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2020ApJ...891..100S | Dynamic Potential Sputtering of Lunar Analog Material by Solar Wind Ions | Pyroxenes ((Ca, Mg, Fe, Mn)<SUB>2</SUB>Si<SUB>2</SUB>O<SUB>6</SUB>) belong to the most abundant rock forming minerals that make up the surface of rocky planets and moons. Therefore, sputtering of pyroxenes by solar wind ions has to be considered as a very important process for modifying the surface of planetary bodies. This is increased due to potential sputtering by multiply charged ions; to quantify this effect, sputtering of wollastonite (CaSiO<SUB>3</SUB>) by He<SUP>2+</SUP> ions was investigated. Thin films of CaSiO<SUB>3</SUB> deposited on a quartz crystal microbalance were irradiated, allowing precise, in situ, real time sputtering yield measurements. Experimental results were compared with SDTrimSP simulations, which were improved by adapting the used input parameters. On freshly prepared surfaces, He<SUP>2+</SUP> ions show a significant increase in sputtering, as compared to equally fast He<SUP>+</SUP> ions. However, the yield decreases exponentially with fluence, reaching a lower steady state after sputtering of the first few monolayers. Experiments using Ar<SUP>8+</SUP> ions show a similar behavior, which is qualitatively explained by a preferential depletion of surface oxygen due to potential sputtering. A corresponding quantitative model is applied, and the observed potential sputtering behaviors of both He and Ar are reproduced very well. The results of these calculations support the assumption that mainly O atoms are affected by potential sputtering. Based on our findings, we discuss the importance of potential sputtering for the solar wind eroding the lunar surface. Estimated concentration changes and sputtering yields are both in line with previous modeling for other materials, allowing a consistent perspective on the effects of solar wind potential sputtering. | [
1534,
499,
1692,
948,
1024,
2004
] | [
"solar wind",
"exosphere",
"the moon",
"lunar composition",
"mercury (planet)",
"laboratory astrophysics"
] |
2024ApJ...966L...8B | Generation of Low-inclination, Neptune-crossing Trans-Neptunian Objects by Planet Nine | The solar system's distant reaches exhibit a wealth of anomalous dynamical structure, hinting at the presence of a yet-undetected, massive trans-Neptunian body—Planet Nine (P9). Previous analyses have shown how orbital evolution induced by this object can explain the origins of a broad assortment of exotic orbits, ranging from those characterized by high perihelia to those with extreme inclinations. In this work, we shift the focus toward a more conventional class of TNOs and consider the observed census of long-period, nearly planar, Neptune-crossing objects as a hitherto-unexplored probe of the P9 hypothesis. To this end, we carry out comprehensive N-body simulations that self-consistently model gravitational perturbations from all giant planets, the Galactic tide, as well as passing stars, stemming from initial conditions that account for the primordial giant planet migration and Sun's early evolution within a star cluster. Accounting for observational biases, our results reveal that the orbital architecture of this group of objects aligns closely with the predictions of the P9-inclusive model. In stark contrast, the P9-free scenario is statistically rejected at a ∼5σ confidence level. Accordingly, this work introduces a new line of evidence supporting the existence of P9 and further delineates a series of observational predictions poised for near-term resolution. | [
1705,
1184,
2293
] | [
"trans-neptunian objects",
"orbits",
"solar system evolution"
] |
2024PSJ.....5...45C | Leveraging the Gravity Field Spectrum for Icy Satellite Interior Structure Determination: The Case of Europa with the Europa Clipper Mission | Understanding the interior structures of icy moons is pivotal for addressing their origins and habitability. We introduce an approach employing the gravity field spectrum as an additional constraint for the inversion of differentiated icy bodies' interior structures. After developing the general methodology, we apply it to Europa, utilizing the predicted measurement capability of NASA's Europa Clipper mission, and we prove its effectiveness in resolving key geophysical parameters. Notably, we show that using the gravity field spectrum in combination with the mass and moment of inertia of the body allows us to estimate, depending on the considered end-member interior structure, the hydrosphere thickness with 4–20 km uncertainty and reliably determine the seafloor maximum topographic range and elastic thickness to within 100–600 m and 5–15 km, respectively, together with the power–degree relationship of the seafloor topography. We also show that the proposed method allows us to determine the density of the silicate mantle and the radius of the core to within 0.25 g cc<SUP>‑1</SUP> and 50 km, respectively. | [
2189,
1248,
770,
1889,
627,
1255
] | [
"europa",
"planetary interior",
"hydrosphere",
"markov chain monte carlo",
"galilean satellites",
"planetary science"
] |
2022ApJ...932...52H | Inverse Multiview. I. Multicalibrator Inverse Phase Referencing for Microarcsecond Very Long Baseline Interferometry Astrometry | Very Long Baseline Interferometry (VLBI) astrometry is a well established technique for achieving ±10 μas parallax accuracies at frequencies well above 10 GHz. At lower frequencies, uncompensated interferometer delays associated with the ionosphere play the dominant role in limiting the astrometric accuracy. Multiview is a novel VLBI calibration method, which uses observations of multiple quasars to accurately model and remove time-variable, directional-dependent changes to the interferometer delay. Here we extend the Multiview technique by phase-referencing data to the target source ("inverse Multiview") and test its performance. Multiple observations with a four-antenna VLBI array operating at 8.3 GHz show single-epoch astrometric accuracies near 20 μas for target-reference quasar separations up to about 7°. This represents an improvement in astrometric accuracy by up to an order of magnitude compared to standard phase-referencing. | [
1769,
1337,
1713,
1295
] | [
"very long baseline interferometry",
"radio astrometry",
"trigonometric parallax",
"proper motions"
] |
2024ApJS..271...25C | The First LHAASO Catalog of Gamma-Ray Sources | We present the first catalog of very-high-energy and ultra-high-energy gamma-ray sources detected by the Large High Altitude Air Shower Observatory. The catalog was compiled using 508 days of data collected by the Water Cherenkov Detector Array from 2021 March to 2022 September and 933 days of data recorded by the Kilometer Squared Array from 2020 January to 2022 September. This catalog represents the main result from the most sensitive large coverage gamma-ray survey of the sky above 1 TeV, covering decl. from ‑20° to 80°. In total, the catalog contains 90 sources with an extended size smaller than 2° and a significance of detection at >5σ. Based on our source association criteria, 32 new TeV sources are proposed in this study. Among the 90 sources, 43 sources are detected with ultra-high energy (E > 100 TeV) emission at >4σ significance level. We provide the position, extension, and spectral characteristics of all the sources in this catalog. | [
628,
632,
205
] | [
"gamma-ray astronomy",
"gamma-ray observatories",
"catalogs"
] |
2020ApJ...905...34H | The Photospheric Temperatures of Betelgeuse during the Great Dimming of 2019/2020: No New Dust Required | The processes that shape the extended atmospheres of red supergiants, heat their chromospheres, create molecular reservoirs, drive mass loss, and create dust remain poorly understood. Betelgeuse's V-band "Great Dimming" event of 2019 September/2020 February and its subsequent rapid brightening provides a rare opportunity to study these phenomena. Two different explanations have emerged to explain the dimming; new dust appeared in our line of sight attenuating the photospheric light, or a large portion of the photosphere had cooled. Here we present five years of Wing three-filter (A, B, and C band) TiO and near-IR photometry obtained at the Wasatonic Observatory. These reveal that parts of the photosphere had a mean effective temperature (T<SUB>eff</SUB>) significantly lower than that found by Levesque & Massey. Synthetic photometry from MARCS-model photospheres and spectra reveal that the V band, TiO index, and C-band photometry, and previously reported 4000-6800 Å spectra can be quantitatively reproduced if there are multiple photospheric components, as hinted at by Very Large Telescope (VLT)-SPHERE images in Montargès et al. If the cooler component has ΔT<SUB>eff</SUB> ≥ 250 K cooler than 3650 K, then no new dust is required to explain the available empirical constraints. A coincidence of the dominant short- (∼430 days) and long-period (∼5.8 yr) V-band variations occurred near the time of deep minimum (Guinan et al. 2019a). This is in tandem with the strong correlation of V mag and photospheric radial velocities, recently reported by Dupree et al. (2020b). These suggest that the cooling of a large fraction of the visible star has a dynamic origin related to the photospheric motions, perhaps arising from pulsation or large-scale convective motions. | [
988,
1584,
236,
1237,
2119
] | [
"m supergiant stars",
"stellar atmospheres",
"circumstellar dust",
"stellar photospheres",
"atmospheric variability"
] |
2021ApJS..255...21J | Infrared Surface Brightness Fluctuation Distances for MASSIVE and Type Ia Supernova Host Galaxies | We measured high-quality surface brightness fluctuation (SBF) distances for a sample of 63 massive early-type galaxies using the WFC3/IR camera on the Hubble Space Telescope. The median uncertainty on the SBF distance measurements is 0.085 mag, or 3.9% in distance. Achieving this precision at distances of 50-100 Mpc required significant improvements to the SBF calibration and data analysis procedures for WFC3/IR data. Forty-two of the galaxies are from the MASSIVE Galaxy Survey, a complete sample of massive galaxies within ~100 Mpc; the SBF distances for these will be used to improve the estimates of the stellar and central supermassive black hole masses in these galaxies. Twenty-four of the galaxies are Type Ia supernova hosts, useful for calibrating SN Ia distances for early-type galaxies and exploring possible systematic trends in the peak luminosities. Our results demonstrate that the SBF method is a powerful and versatile technique for measuring distances to galaxies with evolved stellar populations out to 100 Mpc and constraining the local value of the Hubble constant. * Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. These observations are associated with GO Programs #11711, #11712, #12450, #14219, #14654, #14771, #14804, #15265, and #15329. | [
590,
394,
395,
456,
651,
915
] | [
"galaxy distances",
"distance indicators",
"distance measure",
"elliptical galaxies",
"giant elliptical galaxies",
"lenticular galaxies"
] |
2020ApJ...892..108P | Iron Line Tomography of General Relativistic Hydrodynamic Accretion around Kerr Black Holes | We consider a temporal response of relativistically broadened line spectrum of iron from black hole accretion irradiated by an X-ray echo under strong gravity. The physical condition of accreting gas is numerically calculated in the context of general relativistic hydrodynamics under steady-state axisymmetry in Kerr geometry. With the onset of a point-like X-ray flare of a short finite duration just above the accretion surface, the gas is assumed to be ionized to produce a neutral iron fluorescent line. Using a fully relativistic ray-tracing approach, the response of line photons due to the X-ray illumination is traced as a function of time and energy for different source configurations around Schwarzschild and Kerr black holes. Our calculations show that the X-ray echo on the accretion surface clearly imprints a characteristic time-variability in the line spectral features depending on those parameters. Simulated line profiles, aimed for the future microcalorimeter missions of large collecting area such as Athena/X-IFU for typical radio-quiet Seyfert galaxies, are presented to demonstrate that state-of-the-art new observations could differentiate various source parameters by such an X-ray tomographic line reverberation. | [
1447,
159,
739,
16,
293,
1963,
14,
1393
] | [
"seyfert galaxies",
"black hole physics",
"high energy astrophysics",
"active galactic nuclei",
"computational astronomy",
"hydrodynamics",
"accretion",
"relativity"
] |
2022ApJ...937...85P | Changes in the Na D<SUB>1</SUB> Absorption Components of η Carinae Provide Clues on the Location of the Dissipating Central Occulter | The Na D absorption doublet in the spectrum of η Carinae is complex, with multiple absorption features associated with the Great Eruption (1840s), the Lesser Eruption (1890s), and the interstellar clouds. The velocity profile is further complicated by the P Cygni profile originating in the system's stellar winds and blending with the He I λ5876 profile. The Na D profile contains a multitude of absorption components, including those at velocities of -145 km s<SUP>-1</SUP>, -168 km s<SUP>-1</SUP>, and +87 km s<SUP>-1</SUP>, which we concentrate on in this analysis. Ground-based spectra recorded from 2008 to 2021 show significant variability of the -145 km s<SUP>-1</SUP> absorption throughout long-term observations. In the high-ionization phases of η Carinae prior to the 2020 periastron passage, this feature disappeared completely but briefly reappeared across the 2020 periastron, along with a second absorption at -168 km s<SUP>-1</SUP>. Over the past few decades, η Carinae has been gradually brightening, which is shown to be caused by a dissipating occulter. The decreasing absorption of the -145 km s<SUP>-1</SUP> component, coupled with similar trends seen in absorptions of ultraviolet resonant lines, indicate that this central occulter was possibly a large clump associated with the Little Homunculus or another clump between the Little Homunculus and the star. We also report on a foreground absorption component at +87 km s<SUP>-1</SUP>. Comparison of Na D absorption in the spectra of nearby systems demonstrates that this redshifted component likely originates in an extended foreground structure consistent with a previous ultraviolet spectral survey in the Carina Nebula. | [
732,
944,
154,
453,
241
] | [
"massive stars",
"luminous blue variable stars",
"binary stars",
"ejecta",
"circumstellar matter"
] |
2023ApJ...959..123B | Investigating APOKASC Red Giant Stars with Abnormal Carbon-to-nitrogen Ratios | The success of galactic archeology and the reconstruction of the formation history of our Galaxy relies critically on precise ages for large populations of stars. For evolved stars in the red clump and red giant branch, the carbon-to-nitrogen ratio ([C/N]) has recently been identified as a powerful diagnostic of mass and age that can be applied to stellar samples from spectroscopic surveys such as Sloan Digital Sky Survey/APOGEE. Here, we show that at least 10% of red clump stars and red giant branch stars deviate from the standard relationship between [C/N] and mass. We use the APOGEE-Kepler (APOKASC) overlap sample to show that binary interactions are responsible for the majority of these outliers and that stars with indicators of current or previous binarity should be excluded from galactic archeology analyses that rely on [C/N] abundances to infer stellar masses. We also show that the Data Release 14 APOGEE analysis overestimates the surface gravities for even moderately rotating giants (vsini > 2 km s<SUP>-1</SUP>). | [
4
] | [
"a giant stars"
] |
2024ApJ...970...51G | Expanded Sample of Small Magellanic Cloud Ultraviolet Dust Extinction Curves: Correlations between the 2175 Å Bump, q <SUB>PAH</SUB>, Ultraviolet Extinction Shape, and N(H I)/A(V) | The Small Magellanic Cloud (SMC) shows a large variation in ultraviolet (UV) dust extinction curves, ranging from Milky Way (MW) like to significantly steeper curves with no detectable 2175 Å bump. This result is based on a sample of only nine sight lines. From Hubble Space Telescope Space Telescope Imaging Spectrograph and IUE spectra of OB stars, we have measured UV extinction curves along 32 SMC sight lines where eight of these curves were published previously. We find 16 sight lines with steep extinction with no detectable 2175 Å bump, four sight lines with MW-like extinction with a detectable 2175 Å bump, two sight lines with fairly flat UV extinction and weak/absent 2175 Å bumps, and 10 sight lines with unreliable curves due to low SMC dust columns. Our expanded sample shows that the sight lines with and without the 2175 Å bump are located throughout the SMC and not limited to specific regions. The average extinction curve of the 16 bump-less sight lines is very similar to the previous average based on four sight lines. We find no correlation between dust column and the strength of the 2175 Å bump. We test the hypothesis that the 2175 Å bump is due to the same dust grains that are responsible for the mid-infrared carbonaceous (polycyclic aromatic hydrocarbon) emission features and find they are correlated, confirming recent work in the MW. Overall, the slope of the UV extinction increases as the amplitudes of the 2175 Å bump and far-ultraviolet curvature decrease. Finally, the UV slope is correlated with N(H I)/A(V) and the 2175 Å bump and nonlinear far-ultraviolet rise amplitudes are anticorrelated with N(H I)/A(V). | [
836,
837,
1738,
1468
] | [
"interstellar dust",
"interstellar dust extinction",
"ultraviolet extinction",
"small magellanic cloud"
] |
2020ApJS..250....9S | Lyα Radiative Transfer: Monte Carlo Simulation of the Wouthuysen-Field Effect | A three-dimensional Monte Carlo Lyα radiative transfer (RT) code, named LaRT, is developed to study the Lyα RT and the Wouthuysen-Field (WF) effect. Using the code, we calculate the line profile of Lyα radiation within the multiphase interstellar medium (ISM), with a particular emphasis on gas at low densities. We show that the WF effect is in action: the central portion of the line profile tends to approach a small slice of the Planck function with a color temperature equal to the kinetic temperature of the gas, even in a system with an optical thickness as low as τ<SUB>0</SUB> ≈ 100-500. We also investigate the effects of the turbulent motion of the ISM on the emergent Lyα spectrum and color temperature. The turbulent motion broadens the emergent spectrum, as generally expected, but the color temperature is not affected by the turbulent motion in typical astrophysical environments. We utilize two multiphase ISM models, appropriate for the vicinity of the Sun, to calculate the 21 cm spin temperature of neutral hydrogen, including excitation via the Lyα resonant scattering. The first ISM model is a simple clumpy model, while the second is a self-consistent magnetohydrodynamics simulation model using the TIGRESS framework. Lyα photons originating from both H II regions and the collisionally cooling gas are taken into account. We find that the Lyα radiation field is, in general, likely to be strong enough to bring the 21 cm spin temperature of the warm neutral medium close to the kinetic temperature. The escape fraction of Lyα in our ISM models is estimated to be ≈7%-20%. | [
847,
1335,
1967,
1789,
690,
978
] | [
"interstellar medium",
"radiative transfer",
"radiative transfer simulations",
"warm neutral medium",
"h i line emission",
"lyman-alpha galaxies"
] |
2024AJ....167..114S | Planetary Complexity Revealed by the Joint Differential Entropy of Eigencolors | We propose a measure, the joint differential entropy of eigencolors, for determining the spatial complexity of exoplanets using only spatially unresolved light-curve data. The measure can be used to search for habitable planets, based on the premise of a potential association between life and exoplanet complexity. We present an analysis using disk-integrated light curves from Earth, developed in previous studies, as a proxy for exoplanet data. We show that this quantity is distinct from previous measures of exoplanet complexity due to its sensitivity to spatial information that is masked by features with large mutual information between wavelengths, such as cloud cover. The measure has a natural upper limit and appears to avoid a strong bias toward specific planetary features. This makes it a novel and generalizable method, which, when combined with other methods, can broaden the available indicators of habitability. | [
486,
498,
495,
2023,
695,
496,
2022
] | [
"exoplanet astronomy",
"exoplanets",
"exoplanet structure",
"exoplanet surface variability",
"habitable planets",
"exoplanet surface characteristics",
"exoplanet surface composition"
] |
2024ApJ...963...62G | A Quantum Mechanical Treatment of Electron Broadening in Strong Magnetic Fields. II. Large Enhancements due to Exchange Interactions | We present a quantum treatment of atom–electron collisions in magnetic fields, demonstrating the significant importance of including the effect of exchange that arises from two interacting electrons. We find strange behaviors that are not encountered in collisions without a magnetic field. In high magnetic fields, exchange can lead to orders of magnitude enhancements of collision cross sections. Additionally, the elastic collision cross sections that involve the ground state become comparable to those involving excited states, and states with large orbits have the largest contribution to the collisions. We anticipate significant changes to spectral line broadening in neutron star surfaces and atmospheres. | [
1108,
2099,
2083
] | [
"neutron stars",
"atomic spectroscopy",
"collisional broadening"
] |
2023ApJ...959...78C | Strong Resemblance between Surface and Deep Zonal Winds inside Jupiter Revealed by High-degree Gravity Moments | Jupiter's atmosphere interior is a coupled fluid dynamical system strongly influenced by the rapid background rotation. While the visible atmosphere features east-west zonal winds on the order of ~100 m s<SUP>-1</SUP>, zonal flows in the dynamo region are significantly slower, on the order of ~cm s<SUP>-1</SUP> or less, according to the latest magnetic secular variation analysis. The vertical profile of the zonal flows and the underlying mechanism remain elusive. The latest Juno radio tracking measurements afforded the derivation of Jupiter's gravity field to spherical harmonic degree 40. Here, we use the latest gravity solution to reconstruct Jupiter's deep zonal winds without a priori assumptions about their latitudinal profile. The pattern of our reconstructed deep zonal winds strongly resemble that of the surface wind within ±35° latitude from the equator, in particular the northern off-equatorial jet (NOEJ) and the southern off-equatorial jet. The reconstruction features larger uncertainties in the southern hemisphere due to the north-south asymmetric nature of Juno's trajectory. The amplitude of the reconstructed deep NOEJ matches that of the surface wind when the wind is truncated at a depth ~2500 km, and becomes twice that of the surface wind if the truncation depth is reduced to ~1500 km. Our analysis supports the physical picture in which a prominent part of the surface zonal winds extends into Jupiter's interior significantly deeper than the water cloud layer. | [
873,
1244,
1248,
667
] | [
"jupiter",
"planetary atmospheres",
"planetary interior",
"gravitational fields"
] |
2020ApJ...890...46T | Superflares on Solar-type Stars from the First Year Observation of TESS | Superflares, which are strong explosions on stars, have been well studied with the progress of spacetime-domain astronomy. In this work, we present the study of superflares on solar-type stars using Transiting Exoplanet Survey Satellite (TESS) data. Thirteen sectors of observations during the first year of the TESS mission covered the southern hemisphere of the sky, containing 25,734 solar-type stars. We verified 1216 superflares on 400 solar-type stars through automatic search and visual inspection with 2 minute cadence data. Our result suggests a higher superflare frequency distribution than the result from Kepler. This may be because the majority of TESS solar-type stars in our data set are rapidly rotating stars. The power-law index γ of the superflare frequency distribution ( ${dN}/{dE}\propto {E}^{-\gamma }$ ) is constrained to be γ = 2.16 ± 0.10, which is a little larger than that of solar flares but consistent with the results from Kepler. Because only seven superflares of Sun-like stars are detected, we cannot give a robust superflare occurrence frequency. Four stars were accompanied by unconfirmed hot planet candidates. Therefore, superflares may possibly be caused by stellar magnetic activities instead of planet-star interactions. We also find an extraordinary star, TIC43472154, which exhibits about 200 superflares per year. In addition, the correlation between the energy and duration of superflares ( ${T}_{\mathrm{duration}}\propto {E}^{\beta }$ ) is analyzed. We derive the power-law index to be β = 0.42 ± 0.01, which is a little larger than β = 1/3 from the prediction according to magnetic reconnection theory. | [
1603,
558
] | [
"stellar flares",
"g stars"
] |
2022PASP..134h4101B | Performance Assessment of the KASI-Deep Rolling Imaging Fast-optics Telescope Pathfinder | In a ΛCDM universe, most galaxies evolve by mergers and accretions, leaving faint and/or diffuse structures, such as tidal streams and stellar halos. Although these structures are a good indicator of galaxies' recent mass assembly history, they have the disadvantage of being difficult to observe due to their low surface brightness (LSB). To recover these LSB features by minimizing the photometric uncertainties introduced by the optical system, we developed a new optimized telescope named K-DRIFT pathfinder, adopting a linear astigmatism free-three mirror system. Thanks to the off-axis design, it is expected to avoid the loss and scattering of light on the optical path within the telescope. To assess the performance of this prototype telescope, we investigate the photometric depth and capability to identify LSB features. We find that the surface brightness limit reaches down to μ <SUB> r,1σ </SUB> ~ 28.5 mag arcsec<SUP>-2</SUP> in 10″ × 10″ boxes, enabling us to identify a single stellar stream to the east of NGC 5907. We also examine the characteristics of the point-spread function (PSF) and find that the PSF wing reaches a very low level. Still, however, some internal reflections appear within a radius of ~6' from the center of sources. Despite a relatively small aperture (0.3 m) and short integration time (2 hr), this result demonstrates that our telescope is highly efficient in LSB detection. | [
1080,
1861,
573
] | [
"multiple mirror telescopes",
"astronomy data reduction",
"galaxies"
] |
2020ApJ...899L..24S | The Case for an Early Solar Binary Companion | We show that an equal-mass, temporary binary companion to the Sun in the solar birth cluster at a separation of ∼10<SUP>3</SUP> au would have increased the likelihood of forming the observed population of outer Oort Cloud objects and of capturing Planet Nine. In particular, the discovery of a captured origin for Planet Nine would favor our binary model by an order of magnitude relative to a lone stellar history. Our model predicts an overabundance of dwarf planets, discoverable by Legacy Survey of Space and Time, with similar orbits to Planet Nine, which would result from capture by the stellar binary. | [
154,
1157
] | [
"binary stars",
"oort cloud"
] |
2020ApJ...888...53L | Quasi-periodic Pulsations of Gamma-Ray Emissions from a Solar Flare on 2017 September 6 | We investigate quasi-periodic pulsations (QPPs) of high-energy nonthermal emissions from an X9.3 flare (SOL2017-Sep-06T11:53), the most powerful flare since the beginning of solar cycle 24. The QPPs are identified as a series of regular and repeating peaks in the light curves in the γ- and hard X-ray (HXR) channels recorded by the Konus-Wind, as well as the radio and microwave fluxes measured by the CALLISTO radio spectrograph during the impulsive phase. The periods are determined from the global wavelet and Fourier power spectra as 24-30 s in the HXR and microwave channels, which are associated with nonthermal electrons, and ∼20 s in the γ-ray band related to nonthermal ions. Both nonthermal electrons and ions may be accelerated by repetitive magnetic reconnection during the impulsive phase. However, we could not rule out other mechanisms, such as magnetohydrodynamic oscillation in a sausage mode. The QPP detected in this study is useful for understanding the particle acceleration and dynamic process in solar flares and also bridging the gap between stellar and solar flares because the energy realm of the X9.3 solar flare is almost comparable to a typical stellar flare. | [
1536,
1497,
1515,
1496,
1522
] | [
"solar x-ray emission",
"solar gamma-ray emission",
"solar oscillations",
"solar flares",
"solar radio emission"
] |
2022AJ....164..138S | Revising Properties of Planet-Host Binary Systems. II. Apparent Near-Earth-analog Planets in Binaries Are Often Sub-Neptunes | Identifying rocky planets in or near the habitable zones of their stars (near-Earth analogs) is one of the key motivations of many past and present planet-search missions. The census of near-Earth analogs is important because it informs calculations of the occurrence rate of Earth-like planets, which in turn feed into calculations of the yield of future missions to directly image other Earths. Only a small number of potential near-Earth analogs have been identified, meaning that each planet should be vetted carefully and then incorporated into the occurrence rate calculation. A number of putative near-Earth analogs have been identified within binary-star systems. However, stellar multiplicity can bias measured planetary properties, meaning that apparent near-Earth analogs in close binaries may have different radii or instellations than initially measured. We simultaneously fit unresolved optical spectroscopy, optical speckle and near-IR adaptive optics contrasts, and unresolved photometry and retrieved revised stellar temperatures and radii for a sample of 11 binary Kepler targets that host at least one near-Earth-analog planet, for a total of 17 planet candidates. We found that 10 of the 17 planets in our sample had radii that fell in or above the radius gap, suggesting that they are not rocky planets. Only two planets retained super-Earth radii and stayed in the habitable zone, making them good candidates for inclusion in rocky-planet occurrence rate calculations. *Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. | [
498,
1655,
1000,
154,
1777
] | [
"exoplanets",
"super earths",
"main sequence stars",
"binary stars",
"visual binary stars"
] |
2020ApJ...893...53A | Power-law Pseudo-phase-space Density Profiles of Dark Matter Halos: A Fluke of Physics? | It has been known for nearly 20 yr that the pseudo-phase-space density profile of equilibrium simulated dark matter halos, ρ(r)/σ<SUP>3</SUP>(r), is well described by a power law over three decades in radius, even though both the density ρ(r) and the velocity dispersion σ(r) deviate significantly from power laws. The origin of this scale-free behavior is not understood. It could be an inherent property of self-gravitating collisionless systems, or it could be a mere coincidence. To address the question we work with equilibrium halos and, more specifically, the second derivative of the Jeans equation, which, under the assumptions of (I) the Einasto density profile, (II) the linear velocity anisotropy-density slope relation, and (III) ρ/σ<SUP>3</SUP> ∝ r<SUP>-α</SUP>, can be transformed from a differential equation to a cubic algebraic equation. Relations (I)-(III) are all observed in numerical simulations and are well parameterized by a total of four or six model parameters. We do not consider the dynamical evolution of halos; instead, taking advantage of the fact that the algebraic Jeans equation for equilibrium halos puts relations (I)-(III) on the same footing, we study the (approximate) solutions of this equation in the four- and six-dimensional spaces. We argue that the distribution of best solutions in these parameter spaces is inconsistent with ρ/σ<SUP>3</SUP> ∝ r<SUP>-α</SUP> being a fundamental property of gravitational evolution and conclude that the scale-free nature of this quantity is likely to be a fluke. | [
353,
343,
354
] | [
"dark matter",
"cosmology",
"dark matter density"
] |
2023ApJ...952..128C | Breakdown of the Newton-Einstein Standard Gravity at Low Acceleration in Internal Dynamics of Wide Binary Stars | A gravitational anomaly is found at weak gravitational acceleration g <SUB>N</SUB> ≲ 10<SUP>-9</SUP> m s<SUP>-2</SUP> from analyses of the dynamics of wide binary stars selected from the Gaia DR3 database that have accurate distances, proper motions, and reliably inferred stellar masses. Implicit high-order multiplicities are required and the multiplicity fraction is calibrated so that binary internal motions agree statistically with Newtonian dynamics at a high enough acceleration of ≈10<SUP>-8</SUP> m s<SUP>-2</SUP>. The observed sky-projected motions and separation are deprojected to the 3D relative velocity v and separation r through a Monte Carlo method, and a statistical relation between the Newtonian acceleration g <SUB>N</SUB> ≡ GM/r <SUP>2</SUP> (where M is the total mass of the binary system) and a kinematic acceleration g ≡ v <SUP>2</SUP>/r is compared with the corresponding relation predicted by Newtonian dynamics. The empirical acceleration relation at ≲10<SUP>-9</SUP> m s<SUP>-2</SUP> systematically deviates from the Newtonian expectation. A gravitational anomaly parameter δ <SUB>obs-newt</SUB> between the observed acceleration at g <SUB>N</SUB> and the Newtonian prediction is measured to be: δ <SUB>obs-newt</SUB> = 0.034 ± 0.007 and 0.109 ± 0.013 at g <SUB>N</SUB> ≈ 10<SUP>-8.91</SUP> and 10<SUP>-10.15</SUP> m s<SUP>-2</SUP>, from the main sample of 26,615 wide binaries within 200 pc. These two deviations in the same direction represent a 10σ significance. The deviation represents a direct evidence for the breakdown of standard gravity at weak acceleration. At g <SUB>N</SUB> = 10<SUP>-10.15</SUP> m s<SUP>-2</SUP>, the observed to Newton-predicted acceleration ratio is ${g}_{\mathrm{obs}}/{g}_{\mathrm{pred}}={10}^{\sqrt{2}{\delta }_{\mathrm{obs}-\mathrm{newt}}}=1.43\pm 0.06$ . This systematic deviation agrees with the boost factor that the AQUAL theory predicts for kinematic accelerations in circular orbits under the Galactic external field. | [
154,
661,
1069,
1118
] | [
"binary stars",
"gravitation",
"modified newtonian dynamics",
"non-standard theories of gravity"
] |
2021ApJ...916...14M | Realistic Dispersion of Plasmaspheric Hiss in the Inner Magnetosphere and Its Effect on Wave-induced Electron Scattering Rates | The cold plasma approximation is a common treatment to study wave-particle interactions between plasmaspheric hiss and magnetospheric electrons, which, however, can become a challenge during periods of disturbed geomagnetic activity. To assess the validity of the cold plasma dispersion relation of plasmaspheric hiss, we adopt the cold plasma theory to calculate the wave magnetic field intensities from the electric field intensities observed by Van Allen Probe A from 2012 October 1 to 2018 February 28. Comparisons between the observed and converted hiss magnetic field intensities capture pronounced differences with the enhancement of substorm activity, and exhibit the largest discrepancies on the nightside MLT sector for low-frequency hiss waves. We also use both the hiss dispersion curves derived from the observations and the cold plasma dispersion relation to evaluate hiss-induced electron diffusion coefficients under different substorm activity conditions. The results indicate that the profiles of electron diffusion rates vary considerably for the two hiss dispersion relations and that the differences between them become increasingly distinct with substorm activity intensification. Our study therefore demonstrates that the cold plasma theory can become less reliable for plasmaspheric hiss waves under disturbed geomagnetic circumstances and that the realistic wave dispersion is essential to better quantify the electron scattering effect of hiss waves, which needs to be carefully incorporated into future global simulations of the generation and propagation of plasmaspheric hiss and associated dynamic variability of radiation belt electrons. | [
1758,
997
] | [
"van allen radiation belts",
"planetary magnetospheres"
] |
2022ApJ...940..116C | Evidence for Large-scale Excesses Associated with Low H I Column Densities in the Sky. I. Dust Excess | Where dust and gas are uniformly mixed, atomic hydrogen can be traced through the detection of far-infrared (FIR) or UV emission of dust. We considered, for the origin of discrepancies observed between various direct and indirect tracers of gas outside the Galactic plane, possible corrections to the zero levels of the Planck High Frequency Instrument (HFI) detectors. We set the zero levels of the Planck-HFI skymaps as well as the 100 μm map from COBE/DIRBE and IRAS from the correlation between FIR emission and atomic hydrogen column density excluding regions of lowest gas column density. A modified blackbody model fit to those new zero-subtracted maps led to significantly different maps of the opacity spectral index β and temperature T and an overall increase in the optical depth at 353 GHz τ <SUB>353</SUB> of 7.1 × 10<SUP>-7</SUP> compared to the data release 2 Planck map. When comparing τ <SUB>353</SUB> and the H I column density, we observed a uniform spatial distribution of the opacity outside regions with dark neutral gas and CO except in various large-scale regions of low N <SUB>H I </SUB> that represent 25% of the sky. In those regions, we observed an average dust column density 45% higher than predictions based on N <SUB>H I </SUB> with a maximum of 250% toward the Lockman Hole region. From the average opacity σ <SUB> e353</SUB> = (8.9 ± 0.1) × 10<SUP>-27</SUP> cm<SUP>2</SUP>, we deduced a dust-to-gas mass ratio of 0.53 × 10<SUP>-2</SUP>. We did not see evidence of dust associated with a Reynolds layer of ionized hydrogen. We measured a far-ultraviolet isotropic intensity of 137 ± 15 photons s<SUP>-1</SUP> cm<SUP>-2</SUP> sr<SUP>-1</SUP> Å<SUP>-1</SUP> in agreement with extragalactic flux predictions and a near-ultraviolet isotropic intensity of 378 ± 45 photons s<SUP>-1</SUP> cm<SUP>-2</SUP> sr<SUP>-1</SUP> Å<SUP>-1</SUP> corresponding to twice the predicted flux. | [
847,
857,
412,
529,
1742
] | [
"interstellar medium",
"interstellar thermal emission",
"dust continuum emission",
"far infrared astronomy",
"ultraviolet surveys"
] |
2024AJ....168...55M | Image Deconvolution and Point-spread Function Reconstruction with STARRED: A Wavelet-based Two-channel Method Optimized for Light-curve Extraction | We present STARRED, a point-spread function (PSF) reconstruction, two-channel deconvolution, and light-curve extraction method designed for high-precision photometric measurements in imaging time series. An improved resolution of the data is targeted rather than an infinite one, thereby minimizing deconvolution artifacts. In addition, STARRED performs a joint deconvolution of all available data, accounting for epoch-to-epoch variations of the PSF and decomposing the resulting deconvolved image into a point source and an extended source channel. The output is a high-signal-to-noise-ratio, high-resolution frame combining all data and the photometry of all point sources in the field of view as a function of time. Of note, STARRED also provides exquisite PSF models for each data frame. We showcase three applications of STARRED in the context of the imminent LSST survey and of JWST imaging: (i) the extraction of supernovae light curves and the scene representation of their host galaxy; (ii) the extraction of lensed quasar light curves for time-delay cosmography; and (iii) the measurement of the spectral energy distribution of globular clusters in the "Sparkler," a galaxy at redshift z = 1.378 strongly lensed by the galaxy cluster SMACS J0723.3-7327. STARRED is implemented in JAX, leveraging automatic differentiation and graphics processing unit acceleration. This enables the rapid processing of large time-domain data sets, positioning the method as a powerful tool for extracting light curves from the multitude of lensed or unlensed variable and transient objects in the Rubin-LSST data, even when blended with intervening objects. | [
1910,
1234,
918,
2306
] | [
"deconvolution",
"photometry",
"light curves",
"astronomy image processing"
] |
2022ApJ...939....9M | A Comparison of Global Magnetofrictional Simulations of the 2015 March 20 Solar Eclipse | The solar corona exhibits a wide range of phenomena, from highly non-potential objects such as solar filaments to near-potential structures such as the open magnetic flux. For any global model to be useful in space weather applications, the model must on a single day reproduce all of these phenomena in the same simulation, using the same set of coronal physics and parameters. The purpose of the present paper is to evaluate whether the evolving magnetofrictional model can achieve this goal. Twenty-eight separate simulations are analyzed, where each tries to reproduce both highly non-potential and near-potential phenomena observed in the solar corona on the same day. This day is chosen to be 2015 March 20, the date of the solar eclipse. The study evaluates how the cadence of bipole data, ideal or nonideal coronal physics, and the variety of helicity injection mechanisms affect the accuracy of the simulations. Results show that significantly better agreement arises when using Advective Flux Transport (AFT) synoptic maps to drive the simulations, as compared to 27-day Carrington rotation synoptic maps. Using the nonideal effect of hyperdiffusion leads to the worst agreement with all coronal phenomena. Alternatively, when running either ideal or ohmic diffusion simulations with helicity condensation or bipoles with a self-helicity, a good agreement with both on-disk and limb structures can be found. This suggests that future studies aiming to simulate the corona and reproduce multiple phenomena on a given day should use data products such as AFT and avoid using the nonideal physics of hyperdiffusion. | [
1483,
1503,
1492,
1519
] | [
"solar corona",
"solar magnetic fields",
"solar evolution",
"solar prominences"
] |
2020ApJ...894...67D | Spectroscopic and Asteroseismic Analysis of the Secondary Clump Red Giant HD 226808 | In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars. | [
1577,
2096,
1370,
73
] | [
"stellar abundances",
"high resolution spectroscopy",
"red giant clump",
"asteroseismology"
] |
2024ApJ...963...60P | Discovery of Astrometric Accelerations by Dark Companions in the Globular Cluster ω Centauri | We present results from the search for astrometric accelerations of stars in ω Centauri using 13 yr of regularly scheduled Hubble Space Telescope WFC3/UVIS calibration observations in the cluster core. The high-precision astrometry of ∼160,000 sources was searched for significant deviations from linear proper motion. This led to the discovery of four cluster members and one foreground field star with compelling acceleration patterns. We interpreted them as the result of the gravitational pull by an invisible companion and determined preliminary Keplerian orbit parameters, including the companion's mass. For the cluster members, our analysis suggests periods ranging from 8.8 to 19+ yr and dark companions in the mass range of ∼0.7 to ∼1.4M <SUB>☉</SUB>. At least one companion could exceed the upper mass boundary of white dwarfs and can be classified as a neutron star candidate. | [
80,
656,
761,
756,
154,
1799,
1108,
162,
2360,
1543,
884
] | [
"astrometry",
"globular star clusters",
"hubble space telescope",
"hst photometry",
"binary stars",
"white dwarf stars",
"neutron stars",
"black holes",
"gaia",
"space observatories",
"keplerian orbit"
] |
2021ApJ...921..172Z | Confined and Eruptive Catastrophes of Solar Magnetic Flux Ropes Caused by Mass Loading and Unloading | It is widely accepted that coronal magnetic flux ropes are the core structures of large-scale solar eruptive activities, which have a dramatic impact on the solar-terrestrial system. Previous studies have demonstrated that varying magnetic properties of a coronal flux rope system could result in a catastrophe of the rope, which may trigger solar eruptive activities. Since the total mass of a flux rope also plays an important role in stabilizing the rope, we use 2.5 dimensional magnetohydrodynamic numerical simulations in this article to investigate how a flux rope evolves as its total mass varies. It is found that an unloading process that decreases the total mass of the rope could result in an upward (eruptive) catastrophe in the flux rope system, during which the rope jumps upward and the magnetic energy is released. This indicates that mass unloading processes could initiate the eruption of the flux rope. Moreover, when the system is not too diffusive, there is also a downward (confined) catastrophe that could be caused by mass loading processes via which the total mass accumulates. The magnetic energy, however, is increased during the downward catastrophe, indicating that mass loading processes could cause confined activities that may contribute to the storage of energy before the onset of coronal eruptions. | [
1519,
1496,
1981,
310,
1495,
1475,
1321
] | [
"solar prominences",
"solar flares",
"solar filament eruptions",
"solar coronal mass ejections",
"solar filaments",
"solar activity",
"quiescent solar prominence"
] |
2021AJ....161..128S | Chemical Compositions of Red Giant Stars from Habitable Zone Planet Finder Spectroscopy | We have used the Habitable Zone Planet Finder (HPF) to gather high-resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal branch (RHB) stars, one open cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81-1.28 μm wavelength range of the zyJ bands, partially filling the gap between the optical (0.4-1.0 μm) and infrared (1.5-2.4 μm) spectra already available for the program stars. We derive abundances of 17 species from LTE-based computations involving equivalent widths and spectrum syntheses, and estimate abundance corrections for the species that are most affected by departures from LTE in RHB stars. Generally good agreement is found between HPF-based metallicities and abundance ratios and those from the optical and infrared spectral regions. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C I, P I, S I, K I). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extreme carbon isotope ratio, and one with a rare, very large lithium content. The latter star is unique in our sample in exhibiting very strong He I 10830 Å absorption. The abundances of the open cluster giant concur with those derived from other wavelength regions. Detections of C I and S I in HD 122563 are reported, yielding the lowest metallicity determination of [S/Fe] from more than one multiplet. | [
224,
1031,
1093,
2099,
2048
] | [
"chemical abundances",
"metallicity",
"near infrared astronomy",
"atomic spectroscopy",
"horizontal branch"
] |
2024ApJ...970L..31H | Analyses of Johannes Kepler's Sunspot Drawings in 1607: A Revised Scenario for the Solar Cycles in the Early 17th Century | Telescopic sunspot observations began in 1610 and captured subsequent solar cycles. In combination with proxy reconstructions on an annual scale, these data sets indicate a gradual transition between regular solar cycles and the Maunder Minimum. The telescopic sunspot observations missed the beginning of the first telescopic solar cycle (Solar Cycle ‑13), leaving room for considerable uncertainty as to its temporal evolution. Before these early telescopic observations, however, Kepler made solar observations using camerae obscurae and recorded a sunspot group in three solar drawings in 1607. Here, we make use of Kepler's sunspot drawings and descriptive texts to identify his observational sites and time stamps. We have deprojected his sunspot drawings and compared the reported positions with our calculations of the inclination of the solar equator as seen from these sites at that time. These results locate the reported sunspot group near the solar equator eastward from the central meridian. This contrasts with telescopic sunspot drawings from the 1610s that show sunspot groups in the higher heliographic latitudes. Therefore, what Kepler saw was probably a sunspot group from Solar Cycle ‑14, rather than one from Solar Cycle ‑13. These records allow us to place the beginning of Solar Cycle ‑13 between 1607 and 1610. In comparison with the <SUP>14</SUP>C-based solar-cycle reconstructions, our result supports regular solar-cycle durations around the 1610s, rather than any suggested extreme extensions of the solar-cycle duration(s) around the 1610s. | [
1651,
1650,
1653,
1487,
1015,
1473
] | [
"sunspot groups",
"sunspot cycle",
"sunspots",
"solar cycle",
"maunder minimum",
"solar-terrestrial interactions"
] |
2021ApJ...922....2D | EPIC 228782059: Asteroseismology of What Could Be the Coolest Pulsating Helium-atmosphere White Dwarf (DBV) Known | We present analysis of a new pulsating helium-atmosphere (DB) white dwarf, EPIC 228782059, discovered from 55.1 days of K2 photometry. The long-duration, high-quality light curves reveal 11 independent dipole and quadruple modes, from which we derive a rotational period of 34.1 ± 0.4 hr for the star. An optimal model is obtained from a series of grids constructed using the White Dwarf Evolution Code, which returns M<SUB>*</SUB> = 0.685 ± 0.003M<SUB>⊙</SUB>, T<SUB>eff</SUB> = 21,910 ± 23 K, and $\mathrm{log}g=8.14\pm 0.01$ dex. These values are comparable to those derived from spectroscopy by Koester & Kepler (20,860 ± 160 K, and 7.94 ± 0.03 dex). If these values are confirmed or better constrained by other independent works, it would make EPIC 228782059 one of the coolest pulsating DB white dwarf stars known, and would be helpful for testing different physical treatments of convection, and to further investigate the theoretical instability strip of DB white dwarf stars. | [
358,
1307,
1799,
73,
1234
] | [
"db stars",
"pulsating variable stars",
"white dwarf stars",
"asteroseismology",
"photometry"
] |
2023ApJ...948L..25P | X-Ray Polarization of BL Lacertae in Outburst | We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/γ-ray outburst, a 287 ks observation (2022 November 27-30) was taken using the Imaging X-ray Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from the Neil Gehrels Swift observatory and XMM-Newton in soft X-rays (0.3-10 keV), NuSTAR in hard X-rays (3-70 keV), and optical polarization from the Calar Alto and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the IXPE energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find >99% confidence X-ray polarization ${{\rm{\Pi }}}_{2\mbox{--}4\mathrm{keV}}={21.7}_{-7.9}^{+5.6} \% $ and electric vector polarization angle ψ <SUB>2-4keV</SUB> = -28.°7 ± 8.°7 in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous IXPE BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs. | [
98,
159,
1663,
16,
17,
870,
601,
1390,
289,
1810
] | [
"astrophysical black holes",
"black hole physics",
"supermassive black holes",
"active galactic nuclei",
"active galaxies",
"jets",
"galaxy jets",
"relativistic jets",
"compact radiation sources",
"x-ray astronomy"
] |
2020ApJ...888...46C | Upward Overshooting in Turbulent Compressible Convection. I. Effects of the Relative Stability Parameter, the Prandtl Number, and the Péclet Number | In this paper, we investigate the upward overshooting by three-dimensional numerical simulations. We find that the above convectively stable zone can be partitioned into three layers: the thermal adjustment layer (mixing both entropy and material), the turbulent dissipation layer (mixing material but not entropy), and the thermal dissipation layer (mixing neither entropy nor material). The turbulent dissipation layer is separated from the thermal adjustment layer and the thermal dissipation layer by the first and second zero-points of the vertical velocity correlation. The simulation results are in good agreement with the prediction of the one-dimensional turbulent Reynolds stress model. First, the layer structure is similar. Second, the upper boundary of the thermal adjustment layer is close to the peak of the magnitude of the temperature perturbation. Third, the Péclet number at the upper boundary of the turbulent dissipation layer is close to 1. In addition, we have studied the scalings of the overshooting distance on the relative stability parameter S, the Prandtl number Pr, and the Péclet number Pe. The scaling on S is not unique. The trend is that the overshooting distance decreases with S. Fitting on Pr shows that the overshooting distance increases with Pr. Fitting on Pe shows that the overshooting distance decreases with Pe. Finally, we calculate the ratio of the thickness of the turbulent dissipation layer to that of the thermal adjustment layer. The ratio remains almost constant, with an approximate value of 2.4. | [
301,
1631,
1606,
767,
1592
] | [
"stellar convective zones",
"stellar structures",
"stellar interiors",
"hydrodynamical simulations",
"stellar cores"
] |
2020RNAAS...4..211L | MASTER Follow-up Observations of LIGO GW170104 Event | We present the results of MASTER Global Robotic Net optical observations of the LIGO GW170104 error-box during the LIGO/Virgo O2 run. We observed 3421 square degrees inside 3σ error-field. Dozens of optical transients unrelated to gravitational waves were discovered as the result of MASTER observation strategy, that we presented, including short very bright MASTER optical transients J133017.28+780951.8. | [
1957,
675,
1464,
122,
920
] | [
"transient detection",
"gravitational wave astronomy",
"sky surveys",
"automatic patrol telescopes",
"ligo"
] |
2021ApJ...912...44B | The Color and Brightness of the F-corona Inferred from the 2019 July 2 Total Solar Eclipse | Total solar eclipses (TSEs) provide a unique opportunity to quantify the properties of the K-corona (electrons), F-corona (dust), and E-corona (ions) continuously from the solar surface out to a few solar radii. We apply a novel inversion method to separate emission from the K- and F-corona continua using unpolarized total brightness (tB) observations from five 0.5 nm bandpasses acquired during the 2019 July 2 TSE between 529.5 and 788.4 nm. The wavelength dependence relative to the photosphere (i.e., color) of the F-corona itself is used to infer the tB of the K- and F-corona for each line of sight. We compare our K-corona emission results with the Mauna Loa Solar Observatory (MLSO) K-Cor polarized brightness (pB) observations from the day of the eclipse, and the forward modeled K-corona intensity from the Predictive Science Inc. (PSI) magnetohydrodynamic (MHD) model prediction. Our results are generally consistent with previous work and match both the MLSO data and PSI-MHD predictions quite well, supporting the validity of our approach and of the PSI-MHD model. However, we find that the tB of the F-corona is higher than expected in the low corona, perhaps indicating that the F-corona is slightly polarized—challenging the common assumption that the F-corona is entirely unpolarized. | [
1483,
1489,
1514
] | [
"solar corona",
"solar eclipses",
"solar optical telescopes"
] |
2024PSJ.....5....3S | Bioverse: The Habitable Zone Inner Edge Discontinuity as an Imprint of Runaway Greenhouse Climates on Exoplanet Demographics | Long-term magma ocean phases on rocky exoplanets orbiting closer to their star than the runaway greenhouse threshold-the inner edge of the classical habitable zone-may offer insights into the physical and chemical processes that distinguish potentially habitable worlds from others. The thermal stratification of runaway planets is expected to significantly inflate their atmospheres, potentially providing observational access to the runaway greenhouse transition in the form of a habitable zone inner edge discontinuity in radius-density space. Here, we use Bioverse, a statistical framework combining contextual information from the overall planet population with a survey simulator, to assess the ability of ground- and space-based telescopes to test this hypothesis. We find that the demographic imprint of the runaway greenhouse transition is likely detectable with high-precision transit photometry for sample sizes ≳100 planets if at least ~10% of those orbiting closer than the habitable zone inner edge harbor runaway climates. Our survey simulations suggest that, in the near future, ESA's PLATO mission will be the most promising survey to probe the habitable zone inner edge discontinuity. We determine the survey strategies that maximize the diagnostic power of the obtained data and identify as key mission design drivers: (1) a follow-up campaign of planetary mass measurements and (2) the fraction of low-mass stars in the target sample. Observational constraints on the runaway greenhouse transition will provide crucial insights into the distribution of atmospheric volatiles among rocky exoplanets, which may help to identify the nearest potentially habitable worlds. | [
696,
695,
74,
511,
2184,
487,
1857,
498,
1709,
1332,
1900,
1904
] | [
"habitable zone",
"habitable planets",
"astrobiology",
"extrasolar rocky planets",
"planetary climates",
"exoplanet atmospheres",
"astronomical simulations",
"exoplanets",
"transit photometry",
"radial velocity",
"bayesian statistics",
"parametric hypothesis tests"
] |
2021ApJ...909...74M | The Dragonfly Wide Field Survey. II. Accurate Total Luminosities and Colors of Nearby Massive Galaxies and Implications for the Galaxy Stellar-mass Function | Stellar-mass estimates of massive galaxies are susceptible to systematic errors in their photometry, due to their extended light profiles. In this study, we use data from the Dragonfly Wide Field Survey to accurately measure the total luminosities and colors of nearby massive galaxies. The low surface brightness limits of the survey (μ<SUB>g</SUB> ≈ 31 mag arcsec<SUP>-2</SUP> on a 1' scale) allow us to implement a method, based on integrating the 1D surface brightness profile, that is minimally dependent on any parameterization. We construct a sample of 1188 massive galaxies with $\mathrm{log}{M}_{* }/{M}_{\odot }\gt 10.75$ based on the Galaxy Mass and Assembly (GAMA) survey and measure their total luminosities and g - r colors. We then compare our measurements to various established methods applied to imaging from the Sloan Digital Sky Survey (SDSS), focusing on those favored by the GAMA survey. In general, we find that galaxies are brighter in the r band by an average of ∼0.05 mag and bluer in g - r colors by ∼0.06 mag compared to the GAMA measurements. These two differences have opposite effects on the stellar-mass estimates. The total luminosities are larger by 5% but the mass-to-light ratios are lower by ∼10%. The combined effect is that the stellar-mass estimate of massive galaxies decreases by 7%. This, in turn, implies a small change in the number density of massive galaxies: ≤30% at $\mathrm{log}{M}_{* }/{M}_{\odot }\geqslant 11$ . | [
611,
603,
586,
588
] | [
"galaxy photometry",
"galaxy luminosities",
"galaxy colors",
"galaxy counts"
] |
2021ApJS..255....3A | Radiative Transfer with Opacity Distribution Functions: Application to Narrowband Filters | Modeling of stellar radiative intensities in various spectral passbands plays an important role in stellar physics. At the same time, direct calculation of the high-resolution spectrum and then integration of it over the given spectral passband is computationally demanding due to the vast number of atomic and molecular lines. This is particularly so when employing three-dimensional (3D) models of stellar atmospheres. To accelerate the calculations, one can employ approximate methods, e.g., the use of opacity distribution functions (ODFs). Generally, ODFs provide a good approximation of traditional spectral synthesis, i.e., computation of intensities through filters with strictly rectangular transmission functions. However, their performance strongly deteriorates when the filter transmission noticeably changes within its passband, which is the case for almost all filters routinely used in stellar physics. In this context, the aims of this paper are (a) to generalize the ODFs method for calculating intensities through filters with arbitrary transmission functions, and (b) to study the performance of the standard and generalized ODFs methods for calculating intensities emergent from 3D models of stellar atmospheres. For this purpose we use the newly developed MPS-ATLAS radiative transfer code to compute intensities emergent from 3D cubes simulated with the radiative magnetohydrodynamics code MURaM. The calculations are performed in the 1.5D regime, i.e., along many parallel rays passing through the simulated cube. We demonstrate that the generalized ODFs method allows accurate and fast syntheses of spectral intensities and their center-to-limb variations. | [
1335,
1336,
1584,
1585,
486
] | [
"radiative transfer",
"radiative transfer equation",
"stellar atmospheres",
"stellar atmospheric opacity",
"exoplanet astronomy"
] |
2020ApJ...905...81E | Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids: Final Results | Cepheids in multiple systems provide information on the outcome of the formation of massive stars. They can also lead to exotic end-stage objects. This study concludes our survey of 70 galactic Cepheids using the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) with images at two wavelengths to identify companions closer than 5″. In the entire WFC3 survey we identify 16 probable companions for 13 Cepheids. The 7 Cepheids having resolved candidate companions within 2″ all have the surprising property of themselves being spectroscopic binaries (as compared with a 29% incidence of spectroscopic binaries in the general Cepheid population). This is a strong suggestion that an inner binary is linked to the scenario of a third companion within a few hundred astronomical units. This characteristic is continued for more widely separated companions. Under a model where the outer companion is formed first, it is unlikely that it can anticipate a subsequent inner binary. Rather, it is more likely that a triple system has undergone dynamical interaction, resulting in one star moving outward to its current location. Chandra and Gaia data as well as radial velocities and HST/STIS and IUE spectra are used to derive properties of the components of the Cepheid systems. The colors of the companion candidates show a change in distribution at approximately 2000 au separations, from a range including both hot and cool colors for closer companions, to only low-mass companions for wider separations. <SUP>*</SUP> Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NASA5-26555. <SUP>†</SUP> Based on observations made with the Chandra X-ray Observatory. | [
1081,
818,
218,
1569
] | [
"multiple stars",
"intermediate-type stars",
"cepheid variable stars",
"star formation"
] |
2023ApJ...946....5A | Three-dimensional Global Simulations of Type-II Planet-Disk Interaction with a Magnetized Disk Wind. I. Magnetic Flux Concentration and Gap Properties | Giant planets embedded in protoplanetary disks (PPDs) can create annulus density gaps around their orbits in the type-II regime, potentially responsible for the ubiquity of annular substructures observed in PPDs. Although a substantial amount of works studying type-II planetary migration and gap properties have been published, they have almost exclusively all been conducted under the viscous accretion disk framework. However, recent studies have established magnetized disk winds as the primary mechanism driving disk accretion and evolution, which can coexist with turbulence from the magnetorotational instability (MRI) in the outer PPDs. We conduct a series of 3D global nonideal magnetohydrodynamic (MHD) simulations of type-II planet-disk interactions applicable to the outer PPDs. Our simulations properly resolve the MRI turbulence and accommodate the MHD disk wind. We found that the planet triggers the poloidal magnetic flux concentration around its orbit. The concentrated magnetic flux strongly enhances angular momentum removal in the gap, which is along the inclined poloidal field through a strong outflow emanating from the disk surface outward to the planet gap. The resulting planet-induced gap shape is more similar to an inviscid disk, while being much deeper, which can be understood from a simple inhomogeneous wind torque prescription. The corotation region is characterized by a fast trans-sonic accretion flow that is asymmetric in azimuth about the planet and lacking the horseshoe turns, and the meridional flow is weakened. The torque acting on the planet generally drives inward migration, though the migration rate can be affected by the presence of neighboring gaps through stochastic, planet-free magnetic flux concentration. | [
1966,
1300,
1241,
2206,
2204,
767,
1579
] | [
"magnetohydrodynamical simulations",
"protoplanetary disks",
"planet formation",
"planetary migration",
"planetary-disk interactions",
"hydrodynamical simulations",
"stellar accretion disks"
] |
2020ApJS..248...13G | Energy Level Structure and Transition Data of Er<SUP>2+</SUP> | A majority of Er in the universe is synthesized by the r-process, which can occur in the mergers of neutron stars (NSs). The contribution of this element to the opacity of NS ejecta should be tested, but even the energy levels of first excited configuration have not been fully presented. The main aim of this paper is to present accurate energy levels of the ground [Xe]4f<SUP>12</SUP> and first excited [Xe]4f<SUP>11</SUP>5d configurations of Er<SUP>2+</SUP>. The energy level structure of the Er<SUP>2+</SUP> ion was computed using the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction (RCI) methods, as implemented in the GRASP2018 program package. The Breit interaction, self-energy, and vacuum polarization corrections were included in the RCI computations. The zero-first-order approach was used in the computations. Energy levels with the identification in LS coupling for all (399) states belonging to the [Xe]4f<SUP>12</SUP> and [Xe]4f<SUP>11</SUP>5d configurations are presented. Electric dipole (E1) transition data between the levels of these two configurations are computed. The accuracy of these data is evaluated by studying the behavior of the transition rates as functions of the gauge parameter, as well as by evaluating the cancellation factors. The core electron correlations were studied using different strategies. The rms deviations obtained in this study for states of the ground and excited configurations from the available experimental data are 649 and 754 cm<SUP>-1</SUP>, respectively. | [
2099,
1335,
1585,
2074,
226,
1108
] | [
"atomic spectroscopy",
"radiative transfer",
"stellar atmospheric opacity",
"transition probabilities",
"chemically peculiar stars",
"neutron stars"
] |
2023ApJ...956..110C | Discovery of the Magellanic Stellar Stream Out to 100 kpc | The Magellanic Stream (MS)-an enormous ribbon of gas spanning 140° of the southern sky trailing the Magellanic Clouds-has been exquisitely mapped in the five decades since its discovery. However, despite concerted efforts, no stellar counterpart to the MS has been conclusively identified. This stellar stream would reveal the distance and 6D kinematics of the MS, constraining its formation and the past orbital history of the Clouds. We have been conducting a spectroscopic survey of the most distant and luminous red giant stars in the Galactic outskirts. From this data set, we have discovered a prominent population of 13 stars matching the extreme angular momentum of the Clouds, spanning up to 100° along the MS at distances of 60-120 kpc. Furthermore, these kinematically selected stars lie along an [α/Fe]-deficient track in chemical space from -2.5 < [Fe/H] <- 0.5, consistent with their formation in the Clouds themselves. We identify these stars as high-confidence members of the Magellanic Stellar Stream. Half of these stars are metal-rich and closely follow the gaseous MS, whereas the other half are more scattered and metal-poor. We argue that the metal-rich stream is the recently formed tidal counterpart to the MS, and we speculate that the metal-poor population was thrown out of the SMC outskirts during an earlier interaction between the Clouds. The Magellanic Stellar Stream provides a strong set of constraints-distances, 6D kinematics, and birth locations-that will guide future simulations toward unveiling the detailed history of the Clouds. | [
903,
990,
991,
1468,
2166
] | [
"large magellanic cloud",
"magellanic clouds",
"magellanic stream",
"small magellanic cloud",
"stellar streams"
] |
2024RNAAS...8...82G | Classifying Emission-line Galaxies Using a Dense Neural Network and Support Vector Machine | In this study we present an innovative approach to classifying emission-line galaxies, specifically categorizing them as Star-forming, Seyfert, Low Ionization Nuclear Emission Line Regions, or Composites. Leveraging both a Dense Neural Network and Support Vector Machine, we use key emission-line flux ratios as input features extracted from the Baryon Oscillation Spectroscopic Survey data within the Sloan Digital Sky Survey. The high accuracy in classification for both Machine Learning models showcases their effectiveness and viability in accurately classifying emission-line galaxies with slightly different inputs and target classifications compared to past Machine Learning models. | [
2171,
459,
1907,
1936,
1933
] | [
"galaxy spectroscopy",
"emission line galaxies",
"classification",
"support vector machine",
"neural networks"
] |
2023AJ....165...37L | A Census of the Taurus Star-forming Region and Neighboring Associations with Gaia | I have used high-precision photometry and astrometry from the third data release of Gaia to perform a survey for members of the Taurus star-forming region and young associations in its vicinity. This work has produced a new catalog of 532 adopted members of Taurus, which has only minor changes relative to the previous catalog from Esplin & Luhman. I have used the Gaia astrometry to divide the Taurus members into 13 groups that have distinct kinematics. Meanwhile, I have identified 1378 candidate members of seven associations near Taurus. All of these associations have histograms of spectral types that peak near M5 (~0.15 M <SUB>⊙</SUB>), resembling other young populations in the solar neighborhood. For the Taurus groups and neighboring associations, I have estimated ages from their sequences of low-mass stars in Hertzsprung-Russell diagrams. Most of the Taurus groups have median ages of ~1-3 Myr, while the associations have ages ranging from 13 to 56 Myr. I have used mid-infrared photometry from the Wide-field Infrared Survey Explorer to search for excess emission from circumstellar disks among the candidate members of the associations. Disks are detected for 51 stars, 20 of which are reported for the first time in this work. Some recent studies have proposed that samples of older stars (≳10 Myr) found in the vicinity of Taurus represent a distributed population that is associated with the Taurus cloud complex. However, I find that most of those stars have kinematics that are inconsistent with any relationship with Taurus. <SUP>*</SUP> Based on observations made with the Gaia mission, the Two Micron All Sky Survey, the Wide-field Infrared Survey Explorer, the LAMOST survey, the Sloan Digital Sky Survey IV, the NASA Infrared Telescope Facility, and Gemini Observatory. | [
1565,
1582,
1140,
235,
796,
1300,
2050
] | [
"star forming regions",
"stellar associations",
"ob associations",
"circumstellar disks",
"initial mass function",
"protoplanetary disks",
"low mass stars"
] |
2020ApJ...901L..25S | OGLE-GAL-ACEP-091: The First Known Multi-mode Anomalous Cepheid | Anomalous Cepheids (ACs) are metal-deficient, core-helium-burning pulsating stars with masses in the range 1.2-2.2 ${M}_{\odot }$ . Until recently, all known ACs were pure single-mode pulsators. The first candidate for an AC pulsating in more than one radial mode—OGLE-GAL-ACEP-091—was recently identified in the Milky Way based on the photometric database of the Optical Gravitational Lensing Experiment (OGLE) survey. We analyze this object showing that it is actually a triple-mode pulsator. Its position in the Petersen diagram, the light-curve morphology quantified by Fourier coefficients, and absolute magnitudes derived from the Gaia parallax are consistent with the assumption that OGLE-GAL-ACEP-091 is an AC. Our grid of linear pulsation models indicates that OGLE-GAL-ACEP-091 is a 1.8 ${M}_{\odot }$ star with a metallicity of about [Fe/H] = -0.5 dex. | [
2106,
1078,
1307
] | [
"anomalous cepheid variable stars",
"multi-periodic pulsation",
"pulsating variable stars"
] |
2023ApJ...945..134B | Constraining a Model of the Radio Sky below 6 MHz Using the Parker Solar Probe/FIELDS Instrument in Preparation for Upcoming Lunar-based Experiments | We present a Bayesian analysis of data from the FIELDS instrument on board the Parker Solar Probe (PSP) spacecraft with the aim of constraining low-frequency (≲6 MHz) sky in preparation for several upcoming lunar-based experiments. We utilize data recorded during PSP's coning roll maneuvers, in which the axis of the spacecraft is pointed 45° off of the Sun. The spacecraft then rotates about a line between the Sun and the spacecraft with a period of 24 minutes. We reduce the data into two formats: roll-averaged, in which the spectra are averaged over the roll, and phase-binned, in which the spectra are binned according to the phase of the roll. We construct a forward model of the FIELDS observations that includes numerical simulations of the antenna beam, an analytic emissivity function of the galaxy, and estimates of the absorption due to free electrons. Fitting 5 parameters, we find that the roll-averaged data can be fit well by this model, and we obtain posterior parameter constraints that are in general agreement with previous estimates. The model is not, however, able to fit the phase-binned data well, likely due to limitations such as the lack of nonsmooth emission structure at both small and large scales, enforced symmetry between the northern and southern galactic hemispheres, and large uncertainties in the free electron density. This suggests that significant improvement in the low-frequency sky model is needed in order to fully and accurately represent the sky at frequencies below 6 MHz. | [
1338,
1858,
1900,
1894,
343,
856,
831
] | [
"radio astronomy",
"astronomy data analysis",
"bayesian statistics",
"nested sampling",
"cosmology",
"interstellar synchrotron emission",
"interstellar absorption"
] |
2021ApJ...912L..25J | Raining in MKW 3 s: A Chandra-MUSE Analysis of X-Ray Cold Filaments around 3CR 318.1 | We present the analysis of X-ray and optical observations of gas filaments observed in the radio source 3CR 318.1, associated with NGC 5920, the brightest cluster galaxy (BCG) of MKW 3 s, a nearby cool core galaxy cluster. This work is one of the first X-ray and optical analyses of filaments in cool core clusters carried out using MUSE observations. We aim at identifying the main excitation processes responsible for the emission arising from these filaments. We complemented the optical VLT/MUSE observations, tracing the colder gas phase, with X-ray Chandra observations of the hotter highly ionized gas phase. Using the MUSE observations, we studied the emission line intensity ratios along the filaments to constrain the physical processes driving the excitation, and, using the Chandra observations, we carried out a spectral analysis of the gas along these filaments. We found a spatial association between the X-ray and optical morphology of these filaments, which are colder and have lower metal abundance than the surrounding intracluster medium (ICM), as already seen in other BCGs. Comparing with previous results from the literature for other BCGs, we propose that the excitation process that is most likely responsible for these filaments emission is a combination of star formation and shocks, with a likely contribution from self-ionizing, cooling ICM. Additionally, we conclude that the filaments most likely originated from AGN-driven outflows in the direction of the radio jet. | [
16,
2134,
584,
302
] | [
"active galactic nuclei",
"radio active galactic nuclei",
"galaxy clusters",
"cool cores"
] |
2022ApJ...940..164C | An Atmospheric Retrieval of the Brown Dwarf Gliese 229B | We present results from an atmospheric retrieval analysis of Gl 229B using the Brewster retrieval code. We find the best fit model to be cloud-free, consistent with the T dwarf retrieval work of Line et al.; Zalesky et al. and Gonzales et al. Fundamental parameters (mass, radius, log(L <SUB>Bol</SUB> /L <SUB>Sun</SUB>), log(g)) determined from our model agree within 1σ to SED-derived values, except for T <SUB>eff</SUB> where our retrieved T <SUB>eff</SUB> is approximately 100 K cooler than the evolutionary model-based SED value. We find a retrieved mass of ${50}_{-9}^{+12}$ M <SUB>Jup</SUB>, however, we also find that the observables of Gl 229B can be explained by a cloud-free model with a prior on mass at the dynamical value, 70 M <SUB>Jup</SUB> . We are able to constrain abundances for H<SUB>2</SUB>O, CO, CH<SUB>4</SUB>, NH<SUB>3</SUB>, Na and K and find a supersolar C/O ratio as compared to its primary, Gl 229A. We report an overall subsolar metallicity due to atmospheric oxygen depletion, but find a solar [C/H], which matches that of the primary. We find that this work contributes to a growing trend in retrieval-based studies, particularly for brown dwarfs, toward supersolar C/O ratios and discuss the implications of this result on formation mechanisms and internal physical processes, as well as model biases. | [
185,
2120,
291,
555,
1679,
982
] | [
"brown dwarfs",
"atmospheric composition",
"companion stars",
"fundamental parameters of stars",
"t dwarfs",
"m dwarf stars"
] |
2023PSJ.....4....2B | TNO or Comet? The Search for Activity and Characterization of Distant Object 418993 (2009 MS9) | The perihelion of the trans-Neptunian object (TNO) 2009 MS9 brings it close to the distance where some long-period comets are seen to become active. Knowing this, and the fact that this object appears to brighten in excess of its predicted nucleus brightness, suggests that 2009 MS9 has a delayed onset of activity brought on by the sublimation of a species more volatile than water. In this paper, we characterize 2009 MS9's physical properties and investigate potential outgassing through composite images, sublimation models, and measurements of spectral reflectivity. We find that deep composite images of the object at various epochs along its orbit show no evidence of dust yet place sensitive limits to the dust production. We estimate the nucleus radius to be 11.5 ± 3.5 km using thermal IR modeling from NEOWISE data and use this and data pre-perihelion to estimate a geometric albedo of 0.25. We compare a CO sublimation activity model to its post-perihelion heliocentric light curve and find that these data support an active fractional area of 5 × 10<SUP>-6</SUP> assuming 2 μm-sized grains and other typical comet parameters. The spectral reflectivity of the surface materials obtained with the Gemini Observatory and CFHT at different epochs shows a reddening spectral slope. We compare the physical properties of 2009 MS9 to both TNO and comet populations and speculate that 2009 MS9's reddening may be due to the buildup of a dust mantle on the surface and could be an explanation of why TNOs exhibit a color bimodality. | [
2160,
2161,
2162,
1705
] | [
"comet nuclei",
"comet surfaces",
"comet volatiles",
"trans-neptunian objects"
] |
2020ApJ...903...65K | Compact Elliptical Galaxies in Different Local Environments: A Mixture of Galaxies with Different Origins? | We present the stellar populations of 138 compact elliptical galaxies (cEs) in the redshift range of z < 0.05 using the Sloan Digital Sky Survey (SDSS) DR12. Our cEs are divided into those with [cE(w)] and without [cE(w/o)] a bright (M<SUB>r</SUB> < -21 mag) host galaxy. We investigated the stellar population properties of cEs based on the Lick line indices extracted from SDSS spectra. cE(w)s show [Z/H] and [α/Fe] distributions skewed toward higher values compared to those of the cE(w/o)s. No statistically significant difference in age distribution was found between the cE(w)s and cE(w/o)s. In the mass-metallicity distribution, cE(w)s deviate from the relation observed for early-type galaxies at a given stellar mass, whereas cE(w/o)s conform to the relation. Based on the different features in the stellar populations of cE(w)s and cE(w/o)s, we can propose two different cE formation channels tracing different original masses of the progenitors. cE(w)s would be the remnant cores of the massive progenitor galaxies whose outer parts are tidally stripped by a massive neighboring galaxy (i.e., a nurture origin). In contrast, cE(w/o)s are likely the faint end of early-type galaxies maintaining in situ evolution in an isolated environment with no massive galaxy nearby (i.e., a nature origin). Our results reinforce the propositions that cEs comprise a mixture of galaxies with two types of origins depending on their local environment. | [
288,
285,
281,
456,
594,
595,
1699,
1622
] | [
"compact objects",
"compact galaxies",
"compact dwarf galaxies",
"elliptical galaxies",
"galaxy evolution",
"galaxy formation",
"tidal interaction",
"stellar populations"
] |
2023ApJ...956...57C | Interstellar Carbonaceous Dust Erosion Induced by X-Ray Irradiation of Water Ice in Star-forming Regions | The chemical inventory of protoplanetary midplanes is the basis for forming planetesimals. Among them, solid-state reactions based on CO/CO<SUB>2</SUB> toward molecular complexity on interstellar dust grains have been studied in theoretical and laboratory work. The physicochemical interactions between ice, constituted mainly of H<SUB>2</SUB>O, and dust surfaces are limited to a few experimental studies focusing on vacuum ultraviolet and cosmic-ray processing. In this work, the erosion of C dust grains induced by X-ray irradiation of H<SUB>2</SUB>O ice was systematically investigated for the first time. The work aims to provide a better understanding of the reaction mechanism using selectively isotope-labeled oxygen/carbon species in kinetic analysis. Ultrahigh vacuum experiments were performed to study the interstellar ice analog on submicron, thick C dust at ~13 K. H<SUB>2</SUB>O or O<SUB>2</SUB> ice was deposited on the presynthesized amorphous C dust and exposed to soft X-ray photons (250-1250 eV). Fourier-transform infrared spectroscopy was used to monitor in situ the newly formed species as a function of the incident photon fluence. Field emission scanning electron microscopy was used to monitor the morphological changes of (non-)eroded carbon samples. The X-ray processing of the ice/dust interface leads to the formation of CO<SUB>2</SUB>, which further dissociates and forms CO. Carbonyl groups are formed by oxygen addition to grain surfaces and are confirmed as intermediate species in the formation process. The yields of CO and CO<SUB>2</SUB> were found to be dependent on the thickness of the carbon layer. The astronomical relevance of the experimental findings is discussed. | [
2268,
75,
838,
2004,
201,
849
] | [
"dust destruction",
"astrochemistry",
"interstellar dust processes",
"laboratory astrophysics",
"carbonaceous grains",
"interstellar molecules"
] |
2022RNAAS...6..155P | Chemical Abundances for 25 JWST Exoplanet Host Stars with KeckSpec | Using a data-driven machine learning tool we report T <SUB>eff</SUB>, $\mathrm{log}(g)$ , $v\sin (i)$ , and elemental abundances for 15 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, Y) for a sample of 25 exoplanet host stars targeted by JWST's first year of observations. The chemical diversity of these stars show that, while a number of their companion planets may have formed in a disk with chemistry similar to Solar, some JWST targets likely experienced different disk compositions. This sample is part of a larger forthcoming catalog that will report homogeneous abundances of ~4500 FGK stars derived from Keck/HIRES optical spectra. | [
224,
2096,
486,
2021,
2130
] | [
"chemical abundances",
"high resolution spectroscopy",
"exoplanet astronomy",
"exoplanet atmospheric composition",
"astrometric exoplanet detection"
] |
2020ApJ...897...23F | Kinematics of the Magellanic Stream and Implications for Its Ionization | The Magellanic Stream and the Leading Arm form a massive, filamentary system of gas clouds surrounding the Large and Small Magellanic Clouds. Here we present a new component-level analysis of their ultraviolet (UV) kinematic properties using a sample of 31 sightlines through the Magellanic System observed with the Hubble Space Telescope/Cosmic Origins Spectrograph. Using Voigt-profile fits to UV metal-line absorption, we quantify the kinematic differences between the low-ion ( $\mathrm{Si}\,\mathrm{II}$ and ${\rm{C}}\,\mathrm{II}$ ), intermediate-ion ( $\mathrm{Si}\,\mathrm{III}$ ), and high-ion ( $\mathrm{Si}\,\mathrm{IV}$ and ${\rm{C}}\,\mathrm{IV}$ ) absorption lines and compare the kinematics between the Stream and Leading Arm. We find that the Stream shows generally simple, single-phase kinematics, with statistically indistinguishable b-value distributions for the low-, intermediate-, and high-ion components, all dominated by narrow ( $b\lesssim 25$ km s<SUP>-1</SUP>) components that are well aligned in velocity. In contrast, we find tentative evidence that the Leading Arm shows complex, multi-phase kinematics, with broader high ions than low ions. These results suggest that the Stream is photoionized up to ${\rm{C}}\,\mathrm{IV}$ by a hard ionizing radiation field. This can be naturally explained by the Seyfert-flare model of Bland-Hawthorn, in which a burst of ionizing radiation from the Galactic Center photoionized the Stream as it passed below the south Galactic pole. The Seyfert flare is the only known source of radiation that is both powerful enough to explain the Hα intensity of the Stream and hard enough to photoionize $\mathrm{Si}\,\mathrm{IV}$ and ${\rm{C}}\,\mathrm{IV}$ to the observed levels. The flare's timescale of a few Myr suggests it is the same event that created the giant X-ray/γ-ray Fermi Bubbles at the Galactic Center. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with programs 11541, 11632, 11524, 11585, 11598, 11686, 12025, 12029, 12038, 12212, 12248, 12275, 12569, 12604, and 14687. | [
735,
594,
565,
991,
1879,
1054,
1052
] | [
"high-velocity clouds",
"galaxy evolution",
"galactic center",
"magellanic stream",
"circumgalactic medium",
"milky way galaxy",
"milky way evolution"
] |
2022ApJ...936...44Z | A Uniform Retrieval Analysis of Ultra-cool Dwarfs. IV. A Statistical Census from 50 Late-T Dwarfs | The spectra of brown dwarfs are key to exploring the chemistry and physics that take place in their atmospheres. Late-T dwarf spectra are particularly diagnostic, due to their relatively cloud-free atmospheres and deep molecular bands. With the use of powerful atmospheric retrieval tools applied to the spectra of these objects, direct constraints on molecular/atomic abundances, gravity, and vertical thermal profiles can be obtained, enabling a broad exploration of the chemical/physical mechanisms operating in their atmospheres. We present a uniform retrieval analysis on low-resolution Infrared Telescope Facility SpeX near-infrared spectra for a sample of 50 T dwarfs, including new observations as part of a recent volume-limited survey. This analysis more than quadruples the sample of T dwarfs with retrieved temperature profiles and abundances (H<SUB>2</SUB>O, CH<SUB>4</SUB>, NH<SUB>3</SUB>, K, and subsequent C/O and metallicities). We are generally able to constrain the effective temperatures to within 50 K, the volume mixing ratios for major species to within 0.25 dex, the atmospheric metallicities [M/H] to within 0.2, and the C/O ratios to within 0.2. We compare our retrieved constraints on the thermal structures, chemistry, and gravities of these objects with predictions from self-consistent radiative-convective equilibrium models and find, in general, though with substantial scatter, consistency with solar composition chemistry and the thermal profiles of the neighboring stellar FGK population. Objects with notable discrepancies between the two modeling techniques and potential mechanisms for their differences, be they related to the modeling approach or physically motivated, are discussed more thoroughly in the text. | [
1679,
2120,
1042,
1031,
185,
1900
] | [
"t dwarfs",
"atmospheric composition",
"methane",
"metallicity",
"brown dwarfs",
"bayesian statistics"
] |
2024ApJ...962...21Z | Cosmic Tidal Reconstruction in Redshift Space | Gravitational coupling between large- and small-scale density perturbations leads to anisotropic distortions to local small-scale matter fluctuations. Such local anisotropic distortions can be used to reconstruct large-scale matter distribution, known as tidal reconstruction. In this paper, we apply the tidal reconstruction methods to simulated galaxies in redshift space. We find that redshift-space distortions (RSDs) lead to anisotropic reconstruction results. While the reconstructed radial modes are more noisy mainly due to the small-scale velocity dispersion, the transverse modes are still reconstructed with high fidelity, and well correlated with the original large-scale density modes. The bias of the reconstructed field at large scales shows a simple angular dependence, which can be described by a form similar to that of the linear RSD. The noise power spectrum is nearly isotropic and scale independent on large scales. This makes the reconstructed tide fields an ideal tracer for cosmic variance cancellation and multi-tracer analysis and has profound implications for future 21 cm intensity mapping surveys. | [
343,
902,
1116
] | [
"cosmology",
"large-scale structure of the universe",
"non-gaussianity"
] |
2023PSJ.....4...28G | Analysis of CN Coma Morphology Features of Comet 21P/Giacobini-Zinner | We analyze jet features found in the coma of comet 21P/Giacobini-Zinner (21P/GZ) during its 2018 perihelion passage using narrowband CN photometric imaging in order to determine the comet's rotational period, and we constrain the CN gas outflow velocity and rotational state through the analysis of azimuthally enhanced morphological features. We find that 21P/GZ has a period of either 7.39 ± 0.01 hr or 10.66 ± 0.01 hr. We measure a lower limit to the outflow velocity for the northern jet of 730 ± 30 m s<SUP>-1</SUP> and for the southern jet of 740 ± 30 m s<SUP>-1</SUP>. We analyze the morphologies of the jet features and determine that the northern jet possesses a corkscrew pattern, and we utilize that knowledge to determine a rotational pole position at an R.A. of ${169}_{-23}^{+{28}^{}}$ deg and a decl. of ${73}_{-11}^{+5}$ deg, with an undetermined sense of rotation. | [
1211,
1959,
1452,
280,
2213
] | [
"period determination",
"lomb-scargle periodogram",
"short period comets",
"comets",
"comet dynamics"
] |
2020ApJ...901L..32F | An Upper Limit on the Spin of SgrA* Based on Stellar Orbits in Its Vicinity | The spin of the massive black hole (BH) at the center of the Milky Way, SgrA*, has been poorly constrained so far. We place an upper limit on the spin of SgrA* based on the spatial distribution of the S-stars, which are arranged in two almost edge-on disks that are located at a position angle of approximately ±45° with respect to the Galactic plane, on a milliparsec scale around the Galactic center. Requiring that the frame-dragging precession has not had enough time to make the S-star orbital angular momentum precess, the spin of the massive BH at the center of the Milky Way can be constrained to χ ≲ 0.1. | [
98,
159,
886,
1663,
565,
1421
] | [
"astrophysical black holes",
"black hole physics",
"kerr black holes",
"supermassive black holes",
"galactic center",
"s stars"
] |
2024ApJ...970...68L | Efficient NIRCam Selection of Quiescent Galaxies at 3 < z < 6 in CEERS | Substantial populations of massive quiescent galaxies at z ≥ 3 challenge our understanding of rapid galaxy growth and quenching over short timescales. In order to piece together this evolutionary puzzle, more statistical samples of these objects are required. Established techniques for identifying massive quiescent galaxies are increasingly inefficient and unconstrained at z > 3. As a result, studies report that as much as 70% of quiescent galaxies at z > 3 may be missed from existing surveys. In this work, we propose a new empirical color selection technique designed to select massive quiescent galaxies at 3 ≲ z ≲ 6 using JWST NIRCam imaging data. We use empirically constrained galaxy spectral energy distribution (SED) templates to define a region in the F277W ‑ F444W versus F150W ‑ F277W color plane that captures quiescent galaxies at z > 3. We apply these color selection criteria to the Cosmic Evolution Early Release Science (CEERS) Survey and use SED fitting on sources in the region to identify 44 candidate z ≳ 3 quiescent galaxies. Over half of these sources are newly discovered and, on average, exhibit specific star formation rates of poststarburst galaxies. Most of these sources would not be discovered using canonical UVJ diagrams. We derive volume density estimates of n ∼ 1–4 × 10<SUP>‑5</SUP> Mpc<SUP>‑3</SUP> at 3 < z < 5, finding excellent agreement with existing reports on similar populations in the CEERS field. Thanks to NIRCam's wavelength coverage and sensitivity, this technique provides an efficient tool to search for large samples of these rare galaxies. | [
2016,
734,
1724
] | [
"quenched galaxies",
"high-redshift galaxies",
"two-color diagrams"
] |
2023ApJ...952...63G | Magnetic Activity-Rotation-Age-Mass Relations in Late-pre-main-sequence Stars | We study the four-dimensional relationships between magnetic activity, rotation, mass, and age for solar-type stars in the age range 5-25 Myr. This is the late-pre-main-sequence (l-PMS) evolutionary phase when rapid changes in a star's interior may lead to changes in the magnetic dynamo mechanisms. We carefully derive rotational periods and spot sizes for 471 members of several l-PMS open clusters using photometric light curves from the Zwicky Transient Facility. Magnetic activity was measured in our previous Chandra-based study, and additional rotational data were obtained from other work. Several results emerge. Mass-dependent evolution of rotation through the l-PMS phase agrees with astrophysical models of stellar angular momentum changes, although the data suggest a subpopulation of stars with slower initial rotations than commonly assumed. There is a hint of the onset of unsaturated tachoclinal dependency of X-ray activity on rotation, as reported by Argiroffi et al., but this result is not confidently confirmed. Both X-ray luminosity and starspot area decrease approximately as t <SUP>-1</SUP> for solar-mass stars, suggesting that spot magnetic fields are roughly constant and l-PMS stars follow the universal solar-scaling law between the X-ray luminosity and surface magnetic flux. Assuming convective dynamos are dominant, theoretical magnetic fluxes fail to reveal the universal law for l-PMS stars that enter late Henyey tracks. Altogether we emerge with a few lines of evidence suggesting that the transition from the turbulent to solar-type dynamo occurs at the later stages of l-PMS evolution as stars approach the zero-age main sequence. | [
1290,
1629,
1461,
1823,
1300,
1610
] | [
"pre-main sequence stars",
"stellar rotation",
"single x-ray stars",
"x-ray stars",
"protoplanetary disks",
"stellar magnetic fields"
] |
2020AJ....159....9H | HD 150382: A Lithium-rich Star at the Early-AGB Stage? | We report the discovery of a lithium-rich giant, HD 150382, a post-red-giant-branch clump star. The atmospheric parameters, the chemical abundances for 17 elements, and the isotopic ratio <SUP>12</SUP>C/<SUP>13</SUP>C were determined using the equivalent width and the spectral synthesis methods. The lithium abundance was determined via spectral synthesis of the Li I resonance doublet at λ 6708 yielding log ɛ(Li)<SUB>NLTE</SUB> = 2.55. The excited-state line at λ 6104 also was analyzed. In addition, we have used theoretical evolutionary tracks to determine the mass and luminosity of HD 150382 and compare it with other well-known lithium-rich giants in the literature. Our results show that HD 150382 is a slowly rotating K-giant star having near-solar metallicity. We also show that HD 150382 is not s-process enriched, which is in agreement with its evolutionary status. Finally, based on the abundance results, we study the possible scenarios of the lithium enrichment. <P />Based on the observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under the agreement with Observatório Nacional and under agreement between Observatório Nacional and Max-Planck Institute für Astronomie. | [
927,
226,
4,
2100,
2096
] | [
"lithium stars",
"chemically peculiar stars",
"a giant stars",
"asymptotic giant branch stars",
"high resolution spectroscopy"
] |
2020ApJ...895...13G | Does Modified Gravity Predict Fast Stellar Bars in Spiral Galaxies? | The evolution of disk galaxies in modified gravity is studied by using high-resolution N-body simulations. More specifically, we use the weak field limit of two modified gravity theories, that is, nonlocal gravity and scalar-tensor-vector gravity, known as MOG, and ignore the existence of a dark matter (DM) halo. We construct the same models as in the standard DM model and compare their dynamics with the galactic models in modified gravity. It turns out that there are serious differences between galactic models in these different viewpoints. For example, we explicitly show that the galactic models in modified gravity host faster bars compared to the DM case, but the final stellar bars are weaker in modified gravity. These facts are not new and have already been reported in our previous simulations for exponential galactic models. Therefore, our main purpose is to show that the above-mentioned differences, with an emphasis on the speed of the bars, are independent of the initial density profile of the adopted disk and halo. To do so, we employ different profiles for the disk and halo and show that the results remain qualitatively independent of the initial galactic models. Moreover, a more accurate method has been used to quantify the kinematic properties of the stellar bars. Our results imply that, contrary to the DM models, bars in modified gravity are fast rotators that never leave the fast-bar region until the end of the simulation. | [
1560,
391,
594,
1428,
1118
] | [
"spiral galaxies",
"disk galaxies",
"galaxy evolution",
"scalar-tensor-vector gravity",
"non-standard theories of gravity"
] |
2022AJ....163..202G | PetroFit: A Python Package for Computing Petrosian Radii and Fitting Galaxy Light Profiles | PetroFit is an open-source Python package based on Astropy and Photutils that can calculate Petrosian profiles and fit galaxy images. It offers end-to-end tools for making accurate photometric measurements, estimating morphological properties, and fitting 2D models to galaxy images. Petrosian metric radii can be used for model parameter estimation and aperture photometry to provide accurate total fluxes. Correction tools are provided for improving Petrosian radii estimates affected by galaxy morphology. PetroFit also provides tools for sampling Astropy-based models (including custom profiles and multicomponent models) onto image grids and enables point-spread function convolution to account for the effects of seeing. These capabilities provide a robust means of modeling and fitting galaxy light profiles. We have made the PetroFit package publicly available on GitHub ( PetroFit/petrofit ) and PyPi (pip install petrofit). | [
1855,
208,
1914,
573
] | [
"astronomy software",
"ccd photometry",
"regression",
"galaxies"
] |
2020ApJ...890..107M | Internal Structure and CO<SUB>2</SUB> Reservoirs of Habitable Water Worlds | Water worlds are water-rich (>1 wt% H<SUB>2</SUB>O) exoplanets. The classical models of water worlds considered layered structures determined by the phase boundaries of pure water. However, water worlds are likely to possess comet-like compositions, with between ∼3 and 30 mol% CO<SUB>2</SUB> relative to water. In this study, we build an interior structure model of habitable (I.e., surface liquid ocean-bearing) water worlds using the latest results from experimental data on the CO<SUB>2</SUB>-H<SUB>2</SUB>O system to explore the CO<SUB>2</SUB> budget and localize the main CO<SUB>2</SUB> reservoirs inside of these planets. We show that CO<SUB>2</SUB> dissolved in the ocean and trapped inside of a clathrate layer cannot accommodate a cometary amount of CO<SUB>2</SUB> if the planet accretes more than 11 wt% of volatiles (CO<SUB>2</SUB> + H<SUB>2</SUB>O) during its formation. If the atmosphere holds more than a negligible amount of the CO<SUB>2</SUB> (>0.01% of the planet mass), the planet will not have a habitable surface temperature. We propose a new, potentially dominant, CO<SUB>2</SUB> reservoir for water worlds: CO<SUB>2</SUB> buried inside of the high-pressure water ice mantle as CO<SUB>2</SUB> ices or (H<SUB>2</SUB>CO<SUB>3</SUB> × H<SUB>2</SUB>O), the monohydrate of carbonic acid. If insufficient amounts of CO<SUB>2</SUB> are sequestered in either this reservoir or the planet's iron core, habitable-zone water worlds could generically be stalled in their cooling before liquid oceans have a chance to condense. | [
1248,
1151,
196,
695,
498,
1150,
770
] | [
"planetary interior",
"ocean planets",
"carbon dioxide",
"habitable planets",
"exoplanets",
"ocean-atmosphere interactions",
"hydrosphere"
] |
2023AJ....165..142K | Multifilter Time-series Observations of Eleven Blue Short-period ATLAS Variable Stars | Eleven periodic variable stars were observed photometrically through two to four filters from the set UBVR <SUB> C </SUB> I <SUB> C </SUB>. Phase-folded data for each star cover full cycles of variation. Spectral energy distributions, based on absolute photometry extracted from the literature, are used to inform models of the stars. The stars include four eclipsing systems with hot subdwarfs of spectral type O or B (sdO/B). Periods are in the range 1.8-2.2 hr. Four reflection-effect binaries, with amplitudes as large as 0.5 mag in the R <SUB> C </SUB> filter were observed; periods range from 1.6 to 2.4 hr. In two of these latter systems, the primary stars are also sdB stars, while two have white-dwarf components. In all eight of these binaries the companion stars are probably M dwarfs. The remaining three stars are pulsators: one large-amplitude δ Scuti star previously misclassified as an eclipsing system; one field SX Phe star near the Galactic plane; and one multiperiodic high-luminosity star of unknown type. The amplitude is usually a strong function of the wavelength in pulsating stars, but this is not the case for the high-luminosity variable. One possible explanation is that the luminous star has a pulsating companion. The SX Phe and high-luminosity star are both heavily reddened (A <SUB> V </SUB> > 5 mag). | [
2054,
254,
1761
] | [
"subdwarf stars",
"close binary stars",
"variable stars"
] |
2021PSJ.....2...39D | Constraining the Positive Ion Composition in Saturn's Lower Ionosphere with the Effective Recombination Coefficient | The present study combines Radio and Plasma Wave Science/Langmuir Probe and Ion and Neutral Mass Spectrometer data from Cassini's last four orbits into Saturn's lower ionosphere to constrain the effective recombination coefficient α<SUB>300</SUB> from measured number densities and electron temperatures at a reference electron temperature of 300 K. Previous studies have shown an influx of ring material causes a state of electron depletion due to grain charging, which will subsequently affect the ionospheric chemistry. The requirement to take grain charging into account limits the derivation of α<SUB>300</SUB> to upper limits. Assuming photochemical equilibrium and using an established method to calculate the electron production rate, we derive upper limits for α<SUB>300</SUB> of ≲ 3 × 10<SUP>-7</SUP> cm<SUP>3</SUP> s<SUP>-1</SUP> for altitudes below 2000 km. This suggests that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients like HCO<SUP>+</SUP>. An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate coefficients > 5 × 10<SUP>-7</SUP> cm<SUP>3</SUP> s<SUP>-1</SUP> at an electron temperature of 300 K. | [
1255,
1426,
1544,
2072
] | [
"planetary science",
"saturn",
"space plasmas",
"recombination"
] |
2022ApJ...927..128B | On the Spectral Evolution of Hot White Dwarf Stars. II. Time-dependent Simulations of Element Transport in Evolving White Dwarfs with STELUM | White dwarf stars are subject to various element transport mechanisms that can cause their surface composition to change radically as they cool, a phenomenon known as spectral evolution. In this paper, we undertake a comprehensive theoretical investigation of the spectral evolution of white dwarfs. First, we introduce STELUM, a new implementation of the stellar evolutionary code developed at the Université de Montréal. We provide a thorough description of the physical content and numerical techniques of the code, covering the treatment of both stellar evolution and chemical transport. Then, we present two state-of-the-art numerical simulations of element transport in evolving white dwarfs. Atomic diffusion, convective mixing, and mass loss are considered simultaneously as time-dependent diffusive processes and are fully coupled to the cooling. We first model the PG 1159-DO-DB-DQ evolutionary channel: a helium-, carbon-, and oxygen-rich PG 1159 star transforms into a pure-helium DB white dwarf due to gravitational settling and then into a helium-dominated, carbon-polluted DQ white dwarf through convective dredge-up. We also compute for the first time the full DO-DA-DC evolutionary channel: a helium-rich DO white dwarf harboring residual hydrogen becomes a pure-hydrogen DA star through the float-up process and then a helium-dominated, hydrogen-bearing DC star due to convective mixing. We demonstrate that our results are in excellent agreement with available empirical constraints. In particular, our DO-DA-DC simulation perfectly reproduces the lower branch of the bifurcation observed in the Gaia color-magnitude diagram, which can therefore be interpreted as a signature of spectral evolution. | [
1799,
1593,
299,
2046,
1636
] | [
"white dwarf stars",
"stellar diffusion",
"stellar convection envelopes",
"stellar evolutionary models",
"stellar winds"
] |
2021ApJ...907...69L | New Ritz Wavelengths and Transition Probabilities of Parity-forbidden [Mn II] Lines of Astrophysical Interest | We report a comprehensive list of accurate Ritz wavelengths and calculated transition probabilities for parity-forbidden [Mn II] lines. Ritz wavelengths have been derived from experimentally established energy level values resulting from an extensive analysis of a high-resolution Fourier-transform emission spectrum of singly ionized manganese. Our analysis includes transitions between all known metastable and other long-lived levels of Mn II giving a total of 1130 [Mn II] Ritz wavelengths. Our entire list of derived Ritz wavelengths for [Mn II] lines ranges between 237 nm and 170 μm (42,125-58 cm<SUP>-1</SUP>). The accurate Ritz wavelengths and calculated transition probabilities for forbidden lines in this paper are useful in the study and diagnostics of nebulae and other low-density astrophysical plasmas. | [
2064,
2063,
2085,
2082,
2084,
2004,
2093,
2096,
2099
] | [
"atomic data benchmarking",
"atomic physics",
"line positions",
"spectral line lists",
"line intensities",
"laboratory astrophysics",
"theoretical techniques",
"high resolution spectroscopy",
"atomic spectroscopy"
] |
2022ApJ...929..127M | Evolution of Primordial Magnetic Fields during Large-scale Structure Formation | Primordial magnetic fields (PMFs) could explain the large-scale magnetic fields present in the universe. Inflation and phase transitions in the early universe could give rise to such fields with unique characteristics. We investigate the magnetohydrodynamic evolution of these magnetogenesis scenarios with cosmological simulations. We evolve inflation-generated magnetic fields either as (i) uniform (homogeneous) or as (ii) scale-invariant stochastic fields, and phase-transition-generated ones either as (iii) helical or as (iv) nonhelical fields from the radiation-dominated epoch. We find that the final distribution of magnetic fields in the simulated cosmic web shows a dependence on the initial strength and the topology of the seed field. Thus, the observed field configuration retains information on the initial conditions at the moment of the field generation. If detected, PMF observations would open a new window for indirect probes of the early universe. The differences between the competing models are revealed on the scale of galaxy clusters, bridges, as well as filaments and voids. The distinctive spectral evolution of different seed fields produces imprints on the correlation length today. We discuss how the differences between rotation measures from highly ionized regions can potentially be probed with forthcoming surveys. | [
1966,
902,
813,
1294
] | [
"magnetohydrodynamical simulations",
"large-scale structure of the universe",
"intergalactic medium",
"primordial magnetic fields"
] |
2023ApJ...948L..11M | High Tide or Riptide on the Cosmic Shoreline? A Water-rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ 486b from JWST Observations | Planets orbiting M-dwarf stars are prime targets in the search for rocky exoplanet atmospheres. The small size of M dwarfs renders their planets exceptional targets for transmission spectroscopy, facilitating atmospheric characterization. However, it remains unknown whether their host stars' highly variable extreme-UV radiation environments allow atmospheres to persist. With JWST, we have begun to determine whether or not the most favorable rocky worlds orbiting M dwarfs have detectable atmospheres. Here, we present a 2.8-5.2 μm JWST NIRSpec/G395H transmission spectrum of the warm (700 K, 40.3× Earth's insolation) super-Earth GJ 486b (1.3 R <SUB>⊕</SUB> and 3.0 M <SUB>⊕</SUB>). The measured spectrum from our two transits of GJ 486b deviates from a flat line at 2.2σ - 3.3σ, based on three independent reductions. Through a combination of forward and retrieval models, we determine that GJ 486b either has a water-rich atmosphere (with the most stringent constraint on the retrieved water abundance of H<SUB>2</SUB>O > 10% to 2σ) or the transmission spectrum is contaminated by water present in cool unocculted starspots. We also find that the measured stellar spectrum is best fit by a stellar model with cool starspots and hot faculae. While both retrieval scenarios provide equal quality fits ( ${\chi }_{\nu }^{2}=1.0$ ) to our NIRSpec/G395H observations, shorter wavelength observations can break this degeneracy and reveal if GJ 486b sustains a water-rich atmosphere. | [
487,
2021,
2133,
1861,
1244,
1791,
1601,
1584,
2285
] | [
"exoplanet atmospheres",
"exoplanet atmospheric composition",
"transmission spectroscopy",
"astronomy data reduction",
"planetary atmospheres",
"water vapor",
"stellar faculae",
"stellar atmospheres",
"infrared spectroscopy"
] |
2023ApJ...959L..28N | A Primordial Origin for the Gas-rich Debris Disks around Intermediate-mass Stars | While most debris disks consist of dust with little or no gas, a fraction have significant amounts of gas detected via emission lines of CO, ionized carbon, and/or atomic oxygen. Almost all such gaseous debris disks known are around A-type stars with ages up to 50 Myr. We show, using semianalytic disk evolution modeling, that this can be understood if the gaseous debris disks are remnant protoplanetary disks that have become depleted of small grains compared to the interstellar medium. Photoelectric heating by the A stars' far-UV (FUV) radiation is then inefficient, while the stars' extreme-UV (EUV) and X-ray emissions are weak owing to a lack of surface convective zones capable of driving magnetic activity. In this picture, it is relatively difficult for stars outside the range of spectral types from A through early B to have such long-lived gas disks. Less-massive stars have stronger magnetic activity in the chromosphere, transition region, and corona with resulting EUV and X-ray emission, while more-massive stars have photospheres hot enough to produce strong EUV radiation. In both cases, primordial disk gas is likely to photoevaporate well before 50 Myr. These results come from 0D disk evolution models where we incorporate internal accretion stresses, MHD winds, and photoevaporation by EUV and X-ray photons with luminosities that are functions of the stellar mass and age. A key issue this work leaves open is how some disks become depleted in small dust so that FUV photoevaporation slows. Candidates include the grains' growth, settling, radial drift, radiation force, and incorporation into planetary systems. | [
1300,
363,
1599,
2170,
492,
847,
5
] | [
"protoplanetary disks",
"debris disks",
"stellar evolution",
"extreme ultraviolet astronomy",
"exoplanet formation",
"interstellar medium",
"a stars"
] |
2020RNAAS...4...52M | Gaia DR2 Color-Temperature Relations Based on Infrared Flux Method Results | The ESA/Gaia mission is providing accurate and precise all-sky photometry. We combined effective temperatures derived, for a sample of dwarf and giant stars, by Gonzalez Hernandez \& Bonifacio (2009) using the Infrared Flux Method, with the photometry available from the second release of the ESA/Gaia mission. We provide colour-temperature relations for the broad-band colours (BP-RP), (BP-G), (G-RP), (G-K), (BP-K), (RP-K). These relations allow the exploitation of the all-sky Gaia DR2 photometry to obtain precise effective temperatures. | [
1584,
1597
] | [
"stellar atmospheres",
"stellar effective temperatures"
] |
2023AJ....166...48D | The Orbital Eccentricities of Directly Imaged Companions Using Observable-based Priors: Implications for Population-level Distributions | The eccentricity of a substellar companion is an important tracer of its formation history. Directly imaged companions often present poorly constrained eccentricities. A recently developed prior framework for orbit fitting called "observable-based priors" has the advantage of improving biases in derived orbit parameters for objects with minimal phase coverage, which is the case for the majority of directly imaged companions. We use observable-based priors to fit the orbits of 21 exoplanets and brown dwarfs in an effort to obtain the eccentricity distributions with minimized biases. We present the objects' individual posteriors compared to their previously derived distributions, showing in many cases a shift toward lower eccentricities. We analyze the companions' eccentricity distribution at a population level, and compare this to the distributions obtained with the traditional uniform priors. We fit a Beta distribution to our posteriors using observable-based priors, obtaining shape parameters α = ${1.09}_{-0.22}^{+0.30}$ and β = ${1.42}_{-0.25}^{+0.33}$ . This represents an approximately flat distribution of eccentricities. The derived α and β parameters are consistent with the values obtained using uniform priors, though uniform priors lead to a tail at high eccentricities. We find that separating the population into high- and low-mass companions yields different distributions depending on the classification of intermediate-mass objects. We also determine via simulation that the minimal orbit coverage needed to give meaningful posteriors under the assumptions made for directly imaged planets is ≈15% of the inferred period of the orbit. | [
492,
185,
1175,
1177,
509,
1900
] | [
"exoplanet formation",
"brown dwarfs",
"orbit determination",
"orbital elements",
"extrasolar gaseous giant planets",
"bayesian statistics"
] |
2023ApJS..264...11P | On the General Correlation between 3D Solar Wind Speed and Density Model and Solar Proxies | The solar wind (SW) is a supersonic outflow of plasma from the solar corona, with the latitudinal speed and density profiles varying with the solar activity. The SW protons charge exchange with the inflowing interstellar neutral atoms and create energetic neutral atoms (ENAs), which bring information on the physical state of the plasma within the boundary region of the heliosphere. The speed of the ENAs depends on their energies, and consequently observations at different energies provide information on different epochs backward in time. Therefore, understanding the history of the evolution of the SW is important to understand this information. In this paper, we extend the work by Porowski et al., who provided the WawHelioIon 3DSW model of the time evolution of latitudinal profiles of the SW speed and density based on results of analysis of interplanetary scintillations (IPSs). Based on results of principal component analysis, we search for correlation between selected solar proxies and the structure of the SW obtained from IPSs and show that it is possible to reproduce the evolution of the SW structure during the past three solar cycles based on the proxies. With this, we extend the history of the evolution of the SW structure back to 1976, i.e., to the epoch when observations of the key proxies-the inclination of the SW current sheet and the solar polar magnetic fields-became available. We point out the potential of the use of the proxies for forecasting the structure of the SW into the future. | [
1872,
1873,
1476,
1534,
1475,
1580,
711,
106
] | [
"fast solar wind",
"slow solar wind",
"solar physics",
"solar wind",
"solar activity",
"stellar activity",
"heliosphere",
"astrosphere interstellar medium interactions"
] |
2020ApJ...895...54C | Digging for Relics of the Past: The Ancient and Obscured Bulge Globular Cluster NGC 6256 | We used a set of moderately deep and high-resolution optical observations obtained with the Hubble Space Telescope to investigate the properties of the stellar population in the heavily obscured bulge globular cluster (GC) NGC 6256. The analysis of the color-magnitude diagram (CMD) revealed a stellar population with an extended blue horizontal branch severely affected by differential reddening, which was corrected, taking into account color excess variations up to δE(B - V) ∼ 0.51. We implemented a Monte Carlo Markov Chain technique to perform the isochrone fitting of the observed CMD in order to derive the stellar age, the cluster distance, and the average color excess in the cluster direction. Using three different sets of isochrones we found that NGC 6256 is characterized by a very old stellar age around 13.0 Gyr, with a typical uncertainty of ∼0.5 Gyr. We also found an average color excess of E(B - V) = 1.19 and a distance from the Sun of 6.8 kpc. We then derived the cluster gravitational center and measured its absolute proper motion using the Gaia-DR2 catalog. All this was used to back-integrate the cluster orbit in a Galaxy-like potential and measure its integrals of motion. It turned out that NGC 6256 is currently in a low-eccentricity orbit entirely confined within the bulge and its integrals of motion are fully compatible with a cluster purely belonging to the Galaxy native GC population. All these pieces of evidence suggest that NGC 6256 is an extremely old relic of the past history of the Galaxy, formed during the very first stages of its assembly. | [
656,
578,
1054,
2041,
1052,
1053,
756,
1889,
1883,
853,
841
] | [
"globular star clusters",
"galaxy bulges",
"milky way galaxy",
"galactic bulge",
"milky way evolution",
"milky way formation",
"hst photometry",
"markov chain monte carlo",
"algorithms",
"interstellar reddening",
"interstellar extinction"
] |
2022AJ....164..141W | SKYSURF: Constraints on Zodiacal Light and Extragalactic Background Light through Panchromatic HST All-sky Surface-brightness Measurements. I. Survey Overview and Methods | We give an overview and describe the rationale, methods, and testing of the Hubble Space Telescope (HST) Archival Legacy project "SKYSURF." SKYSURF uses HST's unique capability as an absolute photometer to measure the ~0.2-1.7 μm sky-surface brightness (sky-SB) from 249,861 WFPC2, ACS, and WFC3 exposures in ~1400 independent HST fields. SKYSURF's panchromatic data set is designed to constrain the discrete and diffuse UV to near-IR sky components: Zodiacal Light (ZL), Kuiper Belt Objects (KBOs), Diffuse Galactic Light (DGL), and the discrete plus diffuse Extragalactic Background Light (EBL). We outline SKYSURF's methods to: (1) measure sky-SB levels between detected objects; (2) measure the discrete EBL, most of which comes from AB≃17-22 mag galaxies; and (3) estimate how much truly diffuse light may exist. Simulations of HST WFC3/IR images with known sky values and gradients, realistic cosmic ray (CR) distributions, and star plus galaxy counts were processed with nine different algorithms to measure the "Lowest Estimated Sky-SB" (LES) in each image between the discrete objects. The best algorithms recover the LES values within 0.2% when there are no image gradients, and within 0.2%-0.4% when there are 5%-10% gradients. We provide a proof of concept of our methods from the WFC3/IR F125W images, where any residual diffuse light that HST sees in excess of zodiacal model predictions does not depend on the total object flux that each image contains. This enables us to present our first SKYSURF results on diffuse light in Carleton et al. | [
761,
1845,
317,
588,
1568
] | [
"hubble space telescope",
"zodiacal cloud",
"cosmic background radiation",
"galaxy counts",
"star counts"
] |
2024ApJ...968...79L | New Galaxy UV Luminosity Constraints on Warm Dark Matter from JWST | We exploit the recent James Webb Space Telescope (JWST) determination of galaxy UV luminosity functions over the redshift range z = 9–14.5 to derive constraints on warm dark matter (WDM) models. The delayed structure formations in WDM universes make high-redshift observations a powerful probe to set limits on the particle mass m <SUB>x</SUB> of WDM candidates. By integrating these observations with blank-field surveys conducted by the Hubble Space Telescope (HST) at redshifts z = 4–8, we impose constraints on both astrophysical parameters (β, γ, ϵ <SUB>N</SUB>, and M <SUB> c </SUB> for a double-power-law star formation efficiency, and for a Gaussian magnitude–halo mass relation) and the WDM parameter (dark matter particle mass m <SUB>x</SUB>) simultaneously. We find a new limit of m <SUB>x</SUB> ≥ 3.2 keV for the mass of thermal relic WDM particles at a 95% confidence level. This bound is tighter than the most stringent result derived using HST data before. Future JWST observations could further reduce the observation uncertainties and improve this constraint. | [
1787,
942
] | [
"warm dark matter",
"luminosity function"
] |
2020AJ....159..277W | A Numerical Method for Determining the Elements of Circumbinary Orbits and Its Application to Circumbinary Planets and the Satellites of Pluto-Charon | Planets and satellites orbiting a binary system exist in the solar system and extrasolar planetary systems. Their orbits can be significantly different from Keplerian orbits, if they are close to the binary and the secondary-to-primary mass ratio is high. A proper description of a circumbinary orbit is in terms of the free eccentricity e<SUB>free</SUB> at the epicyclic frequency κ<SUB>0</SUB>, forced eccentricity e<SUB>forced</SUB> at the mean motion n<SUB>0</SUB>, and oscillations at higher frequencies forced by the non-axisymmetric components of the binary's potential. We show that accurate numerical values for the amplitudes and frequencies of these terms can be extracted from numerical orbit integrations by applying fast Fourier transformation (FFT) to the cylindrical distance between the circumbinary object and the center of mass of the binary as a function of time. We apply this method to three Kepler circumbinary planets and the satellites of Pluto-Charon. For the satellite Styx of Pluto-Charon, the FFT results for κ<SUB>0</SUB> and e<SUB>free</SUB> differ significantly from the first-order analytic value and the value reported by Showalter & Hamilton, respectively. We show that the deviation in κ<SUB>0</SUB> is likely due to the effect of the 3:1 mean-motion resonance and discuss the implications of the lower value for e<SUB>free</SUB>. | [
154,
211,
1177,
490,
498,
1089,
1267
] | [
"binary stars",
"celestial mechanics",
"orbital elements",
"exoplanet dynamics",
"exoplanets",
"natural satellites (solar system)",
"pluto"
] |
2024ApJ...965...97M | The Diffusion Limit of Photoevaporation in Primordial Planetary Atmospheres | Photoevaporation is thought to play an important role in early planetary evolution. In this study, we investigate the diffusion limit of X-ray- and ultraviolet-induced photoevaporation in primordial atmospheres. We find that compositional fractionation resulting from mass loss is more significant than currently recognized, because it is controlled by the conditions at the top of the atmosphere, where particle collisions are less frequent. Such fractionation at the top of the atmosphere develops a compositional gradient that extends downward. The mass outflow eventually reaches a steady state in which the hydrogen loss is diffusion-limited. We derive new analytic expressions for the diffusion-limited mass-loss rate and the crossover mass. | [
2300,
2309,
22
] | [
"atmospheric dynamics",
"atmospheric structure",
"aeronomy"
] |
2023PSJ.....4...22L | Subsurface Science and Search for Life in Ocean Worlds | Several worlds in our solar system are thought to hold oceans of liquid water beneath their frozen surfaces. These subsurface ice and ocean environments are promising targets in the search for life beyond Earth, but they also present significant new technical challenges to planetary exploration. With a focus on Jupiter's moon Europa, here we (1) identify major benefits and challenges to subsurface ocean world science, (2) provide a multidisciplinary survey of relevant sample handling and life detection technologies, and (3) integrate those perspectives into the Subsurface Science and Search for Life in Ocean Worlds (SSSLOW) concept payload. We discuss scientific goals across three complementary categories: (1) search for life, (2) assess habitability, and (3) investigate geological processes. Major mission challenges considered include submerged operation in high-pressure environments, the need to sample fluids with a range of possible chemical conditions, and detection of biosignatures at low concentrations. The SSSLOW addresses these issues by tightly integrated instrumentation and sample handling systems to enable sequential, complementary measurements while prioritizing preservation of sample context. In this work, we leverage techniques and technologies across several fields to demonstrate a path toward future subsurface exploration and life detection in ice and ocean worlds. | [
2189,
74,
1252
] | [
"europa",
"astrobiology",
"planetary probes"
] |
2021RNAAS...5....8Z | Evidence of Increased Macroturbulence for Betelgeuse during Great Dimming | We compared high-resolution spectra of Betelgeuse observed before and during the Great Dimming. Atomic lines are shallow and broad during the Great Dimming presumably because of molecular veiling and increased macroturbulence, ν<SUB>macro</SUB> ≳ 23 km s<SUP>-1</SUP>. The best fit for TiO bands was found for the MARCS model atmosphere with T<SUB>eff</SUB> = 3500 K. | [
988,
1584,
1624,
2096
] | [
"m supergiant stars",
"stellar atmospheres",
"stellar properties",
"high resolution spectroscopy"
] |
2023ApJ...945L..16M | Prospective Implications of Extreme-ultraviolet Coronal Plumes for Magnetic-network Genesis of Coronal Heating, Coronal-hole Solar Wind, and Solar-wind Magnetic Field Switchbacks | We propose that coronal heating in EUV coronal plumes is weaker, not stronger, than in adjacent nonplume coronal magnetic funnels. This expectation stems from (i) the observation that an EUV plume is born as the magnetic flux at the foot of the plume's magnetic funnel becomes tightly packed, and (ii) the observation that coronal heating in quiet regions increases in proportion to the coastline length of the underlying magnetic network. We do not rule out the possibility that coronal heating in EUV plumes might be stronger, not weaker, but we point out how the opposite is plausible. We reason that increasing coronal heating during plume birth would cause co-temporal increasing net upward mass flux in the plume, whereas decreasing coronal heating during plume birth would cause co-temporal net downward mass flux in quiet-region plumes and co-temporal decrease in net upward mass flux or even net downward mass flux in coronal-hole plumes. We further reason that conclusive evidence of weaker coronal heating in EUV plumes would strengthen the possibility that magnetic-twist waves from fine-scale magnetic explosions at the edges of the magnetic network (1) power much of the coronal heating in quiet regions, and (2) power most of the coronal heating and solar-wind acceleration in coronal holes, with many twist waves surviving to become magnetic field switchbacks in the solar wind from coronal holes. | [
2039,
1989,
1534,
1493,
1484
] | [
"solar coronal plumes",
"solar coronal heating",
"solar wind",
"solar extreme ultraviolet emission",
"solar coronal holes"
] |
2021ApJ...915...87S | Dissecting the Size-Mass and Σ<SUB>1</SUB>-Mass Relations at 1.0 < z < 2.5: Galaxy Mass Profiles and Color Gradients as a Function of Spectral Shape | We study how half-mass radii, central mass densities (Σ<SUB>1</SUB>), and color gradients change as galaxies evolve. We separate ~7000 galaxies into 16 groups with similar spectral shapes; each group represents a different evolutionary stage. We find that different galaxy types populate different regions of both size-mass and Σ<SUB>1</SUB>-mass space. The nine star-forming groups lie along the integrated star-forming Σ<SUB>1</SUB>-mass relation. However, these star-forming groups form steep parallel relations in the size-mass plane, with slopes similar to the quiescent size-mass relation. These steep slopes can be explained as a transformation of the star-forming Σ<SUB>1</SUB>-mass relation and its scatter. We identify three types of transitional galaxies. Green valley and post-starburst galaxies are similarly compact at z > 1.5; however, their distinct color gradients indicate that the two populations represent different pathways to quenching. Post-starburst galaxies have flat color gradients and compact structures, consistent with a fast quenching pathway that requires structural change and operates primarily at high redshift. Green valley galaxies have negative color gradients, and are both larger and more numerous toward lower redshift. These galaxies are consistent with slow quenching without significant structural change. We find that dusty star-forming galaxies at z ≳ 2 are very compact and may represent the "burst" before post-starburst galaxies; at z ≲ 2, dusty star-forming galaxies are extended and have shallow color gradients consistent with slow quenching. Our results suggest that star-forming galaxies grow gradually up the Σ<SUB>1</SUB>-mass relation until (a) they naturally reach the high Σ<SUB>1</SUB> values required for quiescence or (b) a compaction-type event rapidly increases their Σ<SUB>1</SUB>. | [
594,
622,
2040,
2176,
683,
285
] | [
"galaxy evolution",
"galaxy structure",
"galaxy quenching",
"post-starburst galaxies",
"green valley galaxies",
"compact galaxies"
] |
2023PSJ.....4...45R | The Distribution of Molecular Water in the Lunar South Polar Region Based upon 6 μm Spectroscopic Imaging | The amount and distribution of water on the lunar surface are related to the input and production of water by solar wind and meteoroid bombardment, balanced by photodestruction and mobility across the surface. Using the Stratospheric Observatory for Infrared Astronomy (SOFIA), we imaged the 6.1 μm feature that uniquely traces molecular water, covering 1/4 of the lunar nearside surface south of -60° latitude with 5 km resolution on 2022 February 17 UTC. The water feature strength varies significantly across the region, being drier at +28° longitude to more wet (170 ppm) at -7° longitude, and also decreasing toward the pole. Significant local enhancements are found, associated with south-facing, high-altitude topographic features. This includes relatively high H<SUB>2</SUB>O concentrations in a "wet ridge" just north of the Curtius crater; the south-facing, northern, inner rims of the most prominent craters; the south face of the central peak of the Moretus crater; and permanently shadowed polar regions. | [
436,
948,
974
] | [
"earth-moon system",
"lunar composition",
"lunar surface"
] |
2020ApJ...899....6M | Connecting 3D Evolution of Coronal Mass Ejections to Their Source Regions | Since coronal mass ejections (CMEs) are the major drivers of space weather, it is crucial to study their evolution starting from the inner corona. In this work we use graduated cylindrical shell model to study the 3D evolution of 59 CMEs in the inner (<3 R<SUB>⊙</SUB>) and outer (>3 R<SUB>⊙</SUB>) corona using observations from COR-1 and COR-2 on board the Solar TErrestrial RElations Observatory (STEREO) spacecraft. We identify the source regions of these CMEs and classify them as CMEs associated with active regions (ARs), active prominences (APs), and prominence eruptions. We find 27% of CMEs show true expansion and 31% show true deflections as they propagate outwards. Using 3D kinematic profiles of CMEs, we connect the evolution of true acceleration with the evolution of true width in the inner and outer corona, thereby providing observational evidence for the influence of the Lorentz force on the kinematics to lie in the height range 2.5-3 R<SUB>⊙</SUB>. We find a broad range in the distribution of peak 3D speeds and accelerations, ranging from 396 to 2465 km s<SUP>-1</SUP> and 176 to 10,922 m s<SUP>-2</SUP> respectively, with a long tail toward high values coming mainly from CMEs originating from ARs or APs. Further, we find that the magnitude of true acceleration is inversely correlated with its duration with a power-law index of -1.19. We believe that these results will provide important inputs for the planning of upcoming space missions that will observe the inner corona and for models that study CME initiation and propagation. | [
1483,
310,
1974,
1977,
1321
] | [
"solar corona",
"solar coronal mass ejections",
"solar active regions",
"solar active region filaments",
"quiescent solar prominence"
] |
2024ApJ...970...45K | Importance of Initial Condition on Bar Secular Evolution: Role of Halo Angular Momentum Distribution Discontinuity | The dark matter halo properties, for example, mass, spin, and concentration, play a significant role in the formation and evolution of bars in disk galaxies. This study highlights the importance of a new parameter: the dark matter halo angular momentum distribution in the disk's central region. We experiment with N-body galaxy models having a disk and dark matter similar to Milky Way–type galaxies. In these models, we vary the discontinuity of the angular momentum distribution of the halo (the total spin is the same for all models). Our N-body experiments suggest that bar forms in all models after a few Gyr of disk evolution. However, in the secular evolution of the bar, as we evolve these models until 9.78 Gyr, the bar gains its strength in the model with the most continuous halo angular momentum distribution, and the bar loses strength for the most discontinuous halo angular momentum distribution. The secular evolution of the bar suggests that box/peanut/x-shaped bulges similar to those found in the Milky Way disk should be more pronounced in halos with continuous halo angular momentum distributions. This study demonstrates the importance of the initial condition setup of galaxy systems, namely the discontinuity in the dark matter halo angular momentum distribution for a given density distribution, on the bar secular evolution in the disk galaxy simulations. Further, this study helps reconcile the conflicting results of bar secular evolution in a high-spinning halo of the recent literature. | [
136,
2364,
1965,
1083,
1880,
591
] | [
"barred spiral galaxies",
"galaxy bars",
"computational methods",
"n-body simulations",
"galaxy dark matter halos",
"galaxy dynamics"
] |
2023ApJS..268....8K | Type Ia Supernova Nucleosynthesis: Metallicity-dependent Yields | Type Ia supernova explosions (SN Ia) are fundamental sources of elements for the chemical evolution of galaxies. They efficiently produce intermediate-mass (with Z between 11 and 20) and iron group elements-for example, about 70% of the solar iron is expected to be made by SN Ia. In this work, we calculate complete abundance yields for 39 models of SN Ia explosions, based on three progenitors-a 1.4 M <SUB>⊙</SUB> deflagration detonation model, a 1.0 M <SUB>⊙</SUB> double detonation model, and a 0.8 M <SUB>⊙</SUB> double detonation model-and 13 metallicities, with <SUP>22</SUP>Ne mass fractions of 0, 1 × 10<SUP>-7</SUP>, 1 × 10<SUP>-6</SUP>, 1 × 10<SUP>-5</SUP>, 1 × 10<SUP>-4</SUP>, 1 × 10<SUP>-3</SUP>, 2 × 10<SUP>-3</SUP>, 5 × 10<SUP>-3</SUP>, 1 × 10<SUP>-2</SUP>, 1.4 × 10<SUP>-2</SUP>, 5 × 10<SUP>-2</SUP>, and 0.1, respectively. Nucleosynthesis calculations are done using the NuGrid suite of codes, using a consistent nuclear reaction network between the models. Complete tables with yields and production factors are provided online at Zenodo:Yields (https://doi.org/10.5281/zenodo.8060323). We discuss the main properties of our yields in light of the present understanding of SN Ia nucleosynthesis, depending on different progenitor mass and composition. Finally, we compare our results with a number of relevant models from the literature. | [
1728,
1131,
100,
1129
] | [
"type ia supernovae",
"nucleosynthesis",
"astrophysical explosive burning",
"nuclear astrophysics"
] |
2022ApJ...935..162K | Resolving the Core of R136 in the Optical | The sharpest optical images of the R136 cluster in the Large Magellanic Cloud are presented, allowing us for the first time to resolve members of the central core, including R136a1, the most-massive star known. These data were taken using the Gemini speckle imager Zorro in medium-band filters with effective wavelengths similar to BVRI achieving angular resolutions between 30-40 mas. All stars previously known in the literature, having V < 16 mag within the central 2″ × 2″, were recovered. Visual companions (≥40 mas; 2000 au) were detected for the WN5h stars R136 a1 and a3. Photometry of the visual companion of a1 suggests it is of mid-O spectral type. Based on new photometric luminosities using the resolved Zorro imaging, the masses of the individual WN5h stars are estimated to be between 150 and 200 M <SUB>⊙</SUB>, lowering significantly the present-day masses of some of the most-massive stars known. These mass estimates are critical anchor points for establishing the stellar upper-mass function. | [
732,
1569,
1805,
1552
] | [
"massive stars",
"star formation",
"wn stars",
"speckle interferometry"
] |
2020AJ....159..214F | A Multiwavelength Search for Intrinsic Linear Polarization in Wolf-Rayet Winds | Wolf-Rayet stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent interstellar polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ∼0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Strömgren b filter (probing the complex λ4600-4700 emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization. | [
1806,
154,
1278,
1671,
90,
732
] | [
"wolf-rayet stars",
"binary stars",
"polarimetry",
"surveys",
"astronomical reference materials",
"massive stars"
] |
2022ApJ...928..146L | Signatures of a Surviving Helium-star Companion in Type Ia Supernovae and Constraints on the Progenitor Companion of SN 2011fe | Single-degenerate (SD) binary systems composed of a white dwarf and a nondegenerate helium (He)-star companion have been proposed as the potential progenitors of Type Ia supernovae (SNe Ia). The He-star companions are expected to survive the SN Ia explosion in this SD progenitor model. In the present work, we map the surviving He-star companion models computed from our previous three-dimensional hydrodynamical simulations of ejecta-companion interaction into the one-dimensional stellar evolution code Modules for Experiments in Stellar Astrophysics to follow their long-term evolution to make predictions of their post-impact observational properties, which can be helpful in searches for such surviving He-star companions in future observations. By comparing with the very-late-epoch light curve of the best observed SN Ia, SN 2011fe, we find that our surviving He-star companions become significantly more luminous than SN 2011fe about 1000 days after maximum light. This suggests that an He star is very unlikely to be a companion to the progenitor of SN 2011fe. | [
1728,
767,
254,
1599,
715,
291
] | [
"type ia supernovae",
"hydrodynamical simulations",
"close binary stars",
"stellar evolution",
"helium-rich stars",
"companion stars"
] |
2023ApJ...950...82H | Using Dark Energy Explorers and Machine Learning to Enhance the Hobby-Eberly Telescope Dark Energy Experiment | We present analysis using a citizen science campaign to improve the cosmological measures from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the Hubble expansion rate, H(z), and angular diameter distance, D <SUB>A</SUB>(z), at z = 2.4, each to percent-level accuracy. This accuracy is determined primarily from the total number of detected Lyα emitters (LAEs), the false positive rate due to noise, and the contamination due to [O II] emitting galaxies. This paper presents the citizen science project, Dark Energy Explorers (https://www.zooniverse.org/projects/erinmc/dark-energy-explorers), with the goal of increasing the number of LAEs and decreasing the number of false positives due to noise and the [O II] galaxies. Initial analysis shows that citizen science is an efficient and effective tool for classification most accurately done by the human eye, especially in combination with unsupervised machine learning. Three aspects from the citizen science campaign that have the most impact are (1) identifying individual problems with detections, (2) providing a clean sample with 100% visual identification above a signal-to-noise cut, and (3) providing labels for machine-learning efforts. Since the end of 2022, Dark Energy Explorers has collected over three and a half million classifications by 11,000 volunteers in over 85 different countries around the world. By incorporating the results of the Dark Energy Explorers, we expect to improve the accuracy on the D <SUB>A</SUB>(z) and H(z) parameters at z = 2.″4 by 10%-30%. While the primary goal is to improve on HETDEX, Dark Energy Explorers has already proven to be a uniquely powerful tool for science advancement and increasing accessibility to science worldwide. | [
343,
339,
2165,
351
] | [
"cosmology",
"cosmological parameters",
"astronomy education",
"dark energy"
] |
2022AJ....164..245S | Weak Lensing in the Blue: A Counter-intuitive Strategy for Stratospheric Observations | The statistical power of weak lensing measurements is principally driven by the number of high-redshift galaxies whose shapes are resolved. Conventional wisdom and physical intuition suggest this is optimized by deep imaging at long (red or near-IR) wavelengths, to avoid losing redshifted Balmer-break and Lyman-break galaxies. We use the synthetic Emission Line ("EL")-COSMOS catalog to simulate lensing observations using different filters, from various altitudes. Here were predict the number of exposures to achieve a target z ≳ 0.3 source density, using off-the-shelf and custom filters. Ground-based observations are easily better at red wavelengths, as (more narrowly) are space-based observations. However, we find that SUPERBIT, a diffraction-limited observatory operating in the stratosphere, should instead perform its lensing-quality observations at blue wavelengths. | [
670,
584,
583,
738,
1145,
923,
1797
] | [
"gravitational lensing",
"galaxy clusters",
"galaxy cluster counts",
"high altitude balloons",
"observational astronomy",
"limiting magnitude",
"weak gravitational lensing"
] |
2024AJ....167..260W | Classification of Astronomical Spectra Based on Multiscale Partial Convolution | The automated and efficient classification of astronomical spectra is an important research issue in the era of large sky surveys. Most current studies on automatic spectral classification primarily focus on specific data sets and demonstrate outstanding performance. However, the diversity in spectra poses formidable challenges for these classification models, as they exhibit limited capability to generalize across more comprehensive data sets. In response to these challenges, we pioneer a method called the multiscale partial convolution net (MSPC-Net), which amalgamates partial, large kernel, and grouped convolution to facilitate multilabel spectral classification. By harnessing the capabilities of partial convolution, MSPC-Net can effectively reduce the number of model parameters, accelerate the training process, and mitigate the overfitting issue. Integrating large kernel and grouped convolution empowers the model to capture local and global features simultaneously, enhancing its overall classification efficacy. To rigorously evaluate the model's performance, we generate ten different data sets sourced from the Sloan Digital Sky Survey and Large Sky Area Multi-Object Spectroscopic Telescope. These data sets encompass stellar class, stellar subclass, and full classification, providing a comprehensive assessment across various application scenarios. The experimental results reveal that MSPC-Net consistently outperforms the other models across different data sets, especially demonstrating superior performance in the last two data sets with full classification. Consequently, MSPC-Net is poised to find extensive applications in the detailed classification for large-scale sky survey projects. This work not only addresses the challenges of generalization in spectral classification but also contributes significantly to the advancement of robust models for astronomical research. | [
1938,
253,
1858,
1671
] | [
"convolutional neural networks",
"classification systems",
"astronomy data analysis",
"surveys"
] |
2023ApJ...956...88L | Connection between Polytropic Index and Heating | The paper derives the one-to-one connecting relationships between plasma heating and its polytropic index, and addresses the consequences through the transport equation of temperature. Thermodynamic polytropic processes are classified in accordance to their polytropic index, the exponent of the power-law relationship of thermal pressure expressed with respect to density. These processes generalize the adiabatic one, where no heating is exchanged between the system and its environment. We show that, in addition to heating terms, the transport equation of temperature depends on the adiabatic index, instead of a general, nonadiabatic polytropic index, even when the plasma follows nonadiabatic processes. This is because all the information regarding the system's polytropic index is contained in the heating term, even for a nonconstant polytropic index. Moreover, the paper (i) defines the role of the polytropic index in the context of heating; (ii) clarifies the role of the nonadiabatic polytropic index in the transport equation of temperature; (iii) provides an alternative method for deriving the turbulent heating through the comparably simpler polytropic index path; and, finally, (iv) shows a one-component plasma proof-of-concept of this method and discusses the implications of such derived connecting relationships in the solar wind plasma in the heliosphere. | [
1544,
1281,
711
] | [
"space plasmas",
"polytropes",
"heliosphere"
] |
2020ApJ...897..147L | Toward a General Parameterization of the Warm Dark Matter Halo Mass Function | Studies of flux anomalies statistics and perturbations in stellar streams have the potential to constrain models of warm dark matter (WDM), including sterile neutrinos. Producing these constraints requires a parameterization of the WDM mass function relative to that of the cold dark matter (CDM) equivalent. We use five WDM models with half-mode masses, M<SUB>hm</SUB> = [1.3,35] × 10<SUP>8</SUP> ${M}_{\odot }$ , spread across simulations of the Local Group, lensing ellipticals and the z = 2 universe, to generate such a parameterization: we fit parameters to a functional form for the WDM-to-CDM halo mass function ratio, ${n}_{\mathrm{WDM}}({M}_{X})/{n}_{\mathrm{CDM}}({M}_{X})$ , of ${\left(1+{(\alpha {M}_{\mathrm{hm}}/{M}_{X})}^{\beta }\right)}^{\gamma }$ . For M<SUB>X</SUB> ≡ virial mass of central halos we obtain α = 2.3, β = 0.8, and γ = -1.0, and this fit is steeper than the extended Press-Schechter formalism predicts. For M<SUB>X</SUB> ≡ mass of subhalos we instead obtain α = 4.2, β = 2.5, and γ = -0.2; in both mass definitions the scatter is ∼20%. The second fit typically underestimates the relative abundance of z = 2 WDM subhalos at the tens of percent level. We caution that robust constraints will require bespoke simulations and a careful definition of halo mass, particularly for subhalos of mass <10<SUP>8</SUP> ${M}_{\odot }$ . | [
1787
] | [
"warm dark matter"
] |
2023ApJ...945..151T | Ambipolar Heating of Magnetars | Magnetars, neutron stars thought to be with ultrastrong magnetic fields of 10<SUP>14-15</SUP> G, are observed to be much hotter than ordinary pulsars with ~10<SUP>12</SUP> G, and additional heating sources are required. One possibility is heating by the ambipolar diffusion in the stellar core. This scenario is examined by calculating the models using the relativistic thermal evolutionary code without making the isothermal approximation. The results show that this scenario can be consistent with most of the observed magnetar temperature data. | [
992,
1823,
367,
1108
] | [
"magnetars",
"x-ray stars",
"degenerate matter",
"neutron stars"
] |
2022AJ....163..273E | HD 83443c: A Highly Eccentric Giant Planet on a 22 yr Orbit | We report the discovery of a highly eccentric long-period Jovian planet orbiting the hot-Jupiter host HD 83443. By combining radial velocity data from four instruments (AAT/UCLES, Keck/HIRES, HARPS, Minerva-Australis) spanning more than two decades, we find evidence for a planet with m sin $i={1.35}_{-0.06}^{+0.07}$ M <SUB>J</SUB>, moving on an orbit with a = 8.0 ± 0.8 au and eccentricity e = 0.76 ± 0.05. We combine our radial velocity analysis with Gaia eDR3 /Hipparcos proper motion anomalies and derive a dynamical mass of ${1.5}_{-0.2}^{+0.5}{M}_{\mathrm{Jup}}$ . We perform a detailed dynamical simulation that reveals locations of stability within the system that may harbor additional planets, including stable regions within the habitable zone of the host star. HD 83443 is a rare example of a system hosting a hot Jupiter and an exterior planetary companion. The high eccentricity of HD 83443c suggests that a scattering event may have sent the hot Jupiter to its close orbit while leaving the outer planet on a wide and eccentric path. | [
1242,
1332,
486,
490,
1646,
80
] | [
"planet hosting stars",
"radial velocity",
"exoplanet astronomy",
"exoplanet dynamics",
"subgiant stars",
"astrometry"
] |
2021ApJ...916..110L | The Detectability of Kiloparsec-scale Dual Active Galactic Nuclei: The Impact of Galactic Structure and Black Hole Orbital Properties | Observational searches for dual active galactic nuclei (dAGNs) at kiloparsec separations are crucial for understanding the role of galaxy mergers in the evolution of galaxies. In addition, kiloparsec-scale dAGNs may serve as the parent population of merging massive black hole (MBH) binaries, an important source of gravitational waves. We use a semi-analytical model to describe the orbital evolution of unequal mass MBH pairs under the influence of stellar and gaseous dynamical friction in post-merger galaxies. We quantify how the detectability of approximately 40,000 kpc-scale dAGNs depends on the structure of their host galaxies and the orbital properties of the MBH pair. Our models indicate that kiloparsec-scale dAGNs are most likely to be detected in gas-rich post-merger galaxies with smaller stellar bulges and relatively massive, rapidly rotating gas disks. The detectability is also increased in systems with MBHs of comparable masses following low eccentricity prograde orbits. In contrast, dAGNs with retrograde, low eccentricity orbits are some of the least detectable systems among our models. The dAGNs in models in which the accreting MBHs are allowed to exhibit radiative feedback are characterized by a significantly lower overall detectability. The suppression in detectability is most pronounced in gas-rich merger remnant galaxies, where radiation feedback is more likely to arise. If so, then large, relatively gas-poor galaxies may be the best candidates for detecting dAGNs. | [
422,
594,
608,
1663,
2017
] | [
"dynamical friction",
"galaxy evolution",
"galaxy mergers",
"supermassive black holes",
"agn host galaxies"
] |
2020ApJ...904L..12C | Detection of Dynamical Instability in Titan's Thermospheric Jet | Similar to Earth, Saturn's largest moon, Titan, possesses a system of high-altitude zonal winds (or jets) that encircle the globe. Using the Atacama Large Millimeter/submillimeter Array (ALMA) in 2016 August, Lellouch et al. discovered an equatorial jet at much higher altitudes than previously known, with a surprisingly fast speed of up to ∼340 m s<SUP>-1</SUP>; however, the origin of such high velocities is not yet understood. We obtained spectrally and spatially resolved ALMA observations in 2017 May to map Titan's 3D global wind field and compare our results with a re-analysis of the 2016 August data. Doppler wind velocity maps were derived in the altitude range ∼300-1000 km (from the upper stratosphere to the thermosphere). At the highest thermospheric altitudes, a 47% reduction in the equatorial zonal wind speed was measured over the 9 month period (corresponding to L<SUB>s</SUB> = 82°-90° on Titan). This is interpreted as being due to a dramatic slowing and loss of confinement (broadening) of the recently discovered thermospheric equatorial jet, as a result of dynamical instability. These unexpectedly rapid changes in the upper-atmospheric dynamics are consistent with strong variability of the jet's primary driving mechanism. | [
112,
400,
1346
] | [
"atmospheric circulation",
"doppler imaging",
"radio interferometry"
] |
2023ApJ...950L...6L | Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters | It is well known that metal-poor red giant branch (RGB) stars show variations in some elemental abundances, including carbon, due to the internal mixing accompanied by their own in situ CN cycle in the hydrogen burning shell. With our new photometric carbon abundance measurements of RGB stars in M22 and other globular clusters (GCs) in our previous studies, M5, M3, and M92, we derive the carbon depletion rates against the V magnitude, d[C/Fe]/M <SUB> V </SUB>, for individual populations in each GC. We find the metallicity dependence of the carbon depletion rates, d[C/Fe]/M <SUB> V </SUB> ∝ -0.25[Fe/H]. Our results also suggest that the carbon depletion rates of the second generation (SG) of stars are larger than those of the first generation (FG) of stars in our sample GCs, most likely due to different internal temperature profiles with different initial helium abundances between the FG and SG. Our results can provide critical constraints both on understanding the mixing efficiency in the theoretical models, which is largely unknown, and on interpretation of the observational carbon abundance evolution of the bright halo RGB stars. | [
1622,
1284,
656,
725,
224,
1599,
1368,
194
] | [
"stellar populations",
"population ii stars",
"globular star clusters",
"hertzsprung russell diagram",
"chemical abundances",
"stellar evolution",
"red giant branch",
"carbon-nitrogen cycle"
] |
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in Dataset Viewer.
Titles and Abstracts for papers from ADS/SciX that have been tagged with some Unified Astronomy Thesaurus (https://astrothesaurus.org/) keywords.
Bibcode provided for identification.
DatasetDict({
train: Dataset({
features: ['bibcode', 'title', 'abstract', 'verified_uat_ids', 'verified_uat_labels'],
num_rows: 18677
})
val: Dataset({
features: ['bibcode', 'title', 'abstract', 'verified_uat_ids', 'verified_uat_labels'],
num_rows: 3025
})
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For each sample:
'verified_uat_labels'is a list of UAT concept keywords tagged to this paper (by the authors or publisher).'verified_uat_ids'is a list of integers corresponding to the UAT id for each concept above.
It is recommended to use the UAT repository (https://github.com/astrothesaurus/UAT) to match IDs to concepts (these potentially having synonyms) and work on the IDs, not the labels.
Sample:
{
bibcode : '2020ApJ...891..100S',
title : 'Dynamic Potential Sputtering of Lunar Analog Material by Solar Wind Ions',
abstract : 'Pyroxenes ((Ca, Mg, Fe, Mn)<SUB>2</SUB>Si<SUB>2</SUB>O<SUB>6</SUB>) belong to the most abundant rock forming minerals that make up the surface of rocky planets and moons. Therefore, sputtering of pyroxenes by solar wind ions has to be considered as a very important process for modifying the surface of planetary bodies. This is increased due to potential sputtering by multiply charged ions; to quantify this effect, sputtering of wollastonite (CaSiO<SUB>3</SUB>) by He<SUP>2+</SUP> ions was investigated. Thin films of CaSiO<SUB>3</SUB> deposited on a quartz crystal microbalance were irradiated, allowing precise, in situ, real time sputtering yield measurements. Experimental results were compared with SDTrimSP simulations, which were improved by adapting the used input parameters. On freshly prepared surfaces, He<SUP>2+</SUP> ions show a significant increase in sputtering, as compared to equally fast He<SUP>+</SUP> ions. However, the yield decreases exponentially with fluence, reaching a lower steady state after sputtering of the first few monolayers. Experiments using Ar<SUP>8+</SUP> ions show a similar behavior, which is qualitatively explained by a preferential depletion of surface oxygen due to potential sputtering. A corresponding quantitative model is applied, and the observed potential sputtering behaviors of both He and Ar are reproduced very well. The results of these calculations support the assumption that mainly O atoms are affected by potential sputtering. Based on our findings, we discuss the importance of potential sputtering for the solar wind eroding the lunar surface. Estimated concentration changes and sputtering yields are both in line with previous modeling for other materials, allowing a consistent perspective on the effects of solar wind potential sputtering.',
verified_uat_ids : [1534, 499, 1692, 948, 1024, 2004],
verified_uat_labels : ['solar wind', 'exosphere', 'the moon', 'lunar composition', 'mercury (planet)', 'laboratory astrophysics'],
}
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