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SAO/NASA Astrophysics Data System 15

2022ApJ...938..110B

The Pantheon+ Analysis: Cosmological Constraints

We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω<SUB> M </SUB> = 0.334 ± 0.018 from SNe Ia alone. For a flat w <SUB>0</SUB>CDM model, we measure w <SUB>0</SUB> = -0.90 ± 0.14 from SNe Ia alone, H <SUB>0</SUB> = 73.5 ± 1.1 km s<SUP>-1</SUP> Mpc<SUP>-1</SUP> when including the Cepheid host distances and covariance (SH0ES), and w <SUB>0</SUB> = $-{0.978}_{-0.031}^{+0.024}$ when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w <SUB>0</SUB> values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w <SUB>0</SUB> w <SUB> a </SUB>CDM universe, and measure w <SUB> a </SUB> = $-{0.1}_{-2.0}^{+0.9}$ from Pantheon+ SNe Ia alone, H <SUB>0</SUB> = 73.3 ± 1.1 km s<SUP>-1</SUP> Mpc<SUP>-1</SUP> when including SH0ES Cepheid distances, and w <SUB> a </SUB> = $-{0.65}_{-0.32}^{+0.28}$ when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H <SUB>0</SUB> and cannot explain the present "Hubble tension" between local measurements and early universe predictions from the cosmological model.

2021ApJ...916L..12C

The Changing Lightcurve of the Double-mode RR Lyrae Variable Star V338 Boo

We present an analysis of the lightcurve extracted from Transiting Exoplanet Survey Satellite (TESS) Full Frame Images (FFIs) of the double-mode RR Lyrae V338 Boo. We find that the fundamental mode pulsation is changing in amplitude across the 54 days of observations. The first overtone mode pulsation also changes, but on a much smaller scale. Harmonics and combinations of the primary pulsation modes also exhibit unusual behavior. Possible connections with other changes in RR Lyrae pulsations are discussed, but a full understanding of the cause of the changes seen in V338 Boo should shed light on some of the most difficult and unanswered questions in stellar pulsation theory, and astrophysics more generally.

2022ApJ...931...41M

Can X-Ray Observations Improve Optical-UV-based Accretion-rate Estimates for Quasars?

Current estimates of the normalized accretion rates of quasars (L/L <SUB>Edd</SUB>) rely on measuring the velocity widths of broad optical-UV emission lines (e.g., Hβ and Mg II λ2800). However, such lines tend to be weak or inaccessible in the most distant quasars, leading to increasing uncertainty in L/L <SUB>Edd</SUB> estimates at z &gt; 6. Utilizing a carefully selected sample of 53 radio-quiet quasars that have Hβ and C IV λ1549 spectroscopy as well as Chandra coverage, we searched for a robust accretion-rate indicator for quasars, particularly at the highest-accessible redshifts (z ~ 6-7). Our analysis explored relationships between the Hβ-based L/L <SUB>Edd</SUB>, the equivalent width (EW) of C IV, and the optical-to-X-ray spectral slope (α <SUB>ox</SUB>). Our results show that EW(C IV) is the strongest indicator of the Hβ-based L/L <SUB>Edd</SUB> parameter, consistent with previous studies, although significant scatter persists particularly for sources with weak C IV lines. We do not find evidence for the α <SUB>ox</SUB> parameter improving this relation, and we do not find a significant correlation between α <SUB>ox</SUB> and Hβ-based L/L <SUB>Edd</SUB>. This absence of an improved relationship may reveal a limitation of our sample. X-ray observations of additional luminous sources, found at z ≳ 1, may allow us to mitigate the biases inherent in our archival sample and test whether X-ray data could improve L/L <SUB>Edd</SUB> estimates. Furthermore, deeper X-ray observations of our sources may provide accurate measurements of the hard-X-ray power-law photon index (Γ), which is considered an unbiased L/L <SUB>Edd</SUB> indicator. Correlations between EW(C IV) and α <SUB>ox</SUB> with a Γ-based L/L <SUB>Edd</SUB> may yield a more robust prediction of a quasar normalized accretion rate.

2021ApJ...909..144B

UV Spectral Slopes at z = 6-9 in the Hubble Frontier Fields: Lack of Evidence for Unusual or Population III Stellar Populations

We present new measurements of the UV spectral slope β for galaxies at z = 6-9 in the Frontier Field cluster MACS J0416.1-2403 and its parallel field to an unprecedented level of low stellar mass. We fit synthetic stellar population models to the observed spectral energy distribution and calculate β by fitting a power law to the best-fit spectrum. With this method, we report the derivation of rest-frame UV colors of galaxies for the Frontier Fields program extending out to z = 9, probing magnitudes as faint as M<SUB>UV</SUB> = -13.5 at z = 6. We find no significant correlation between β and rest-frame UV magnitude M<SUB>1500</SUB> all redshifts, but we do find a strong correlation between β and stellar mass, with lower-mass galaxies exhibiting bluer UV slopes. At z = 7, the bluest median value of our sample is redder than the previously reported values in the literature, whereas at z = 9, our bluest data point has a median value of $\beta =-{2.63}_{-0.43}^{+0.52}$ . Thus, we find no evidence for extreme stellar populations at z &gt; 6. We also observe a strong correlation between β and star formation rate (SFR), such that galaxies with low SFRs exhibit bluer slopes. Additionally, there exists a star formation main sequence up to z = 9 with SFRs correlating with stellar mass. All of these relations show that β values correlate with a process that drives both the overall SFR and stellar mass assembly. Furthermore, we observe no trend between β and specific SFR, suggesting that β is getting set by a global process driven by the scale of the galaxy.

2024PSJ.....5..161D

Photometric Properties within the Reiner Gamma Swirl: Constraining Formation Mechanisms

The area in the Reiner Gamma swirl studied by Weirich et al. for topographic correlations also displays correlations with the Hapke-model-derived single-scattering albedo, surface roughness, and particle scattering properties with swirl unit. The correlations with single-scattering albedo associate compositional variations in plagioclase and FeO content with swirl unit. The correlations with photometric surface roughness show a rougher surface on-swirl, implying a potentially more porous surface on-swirl compared to off-swirl. This suggests the variations in single-scattering albedo are dominated by the compositional differences and not structural differences, such as compaction. Grain-size differences could still contribute to the albedo variations. Differences in particle scattering properties between on-swirl and off-swirl are counter-indicative of the trend expected from variations in space weathering, unless there is a process to initiate either size sorting or compositional differences. The photometric properties point to a complex interaction of multiple processes to form the swirl units, not a singular dominant process. Variations in weathering, dust mobilization and entrapment, and impact modification may all play a key role.

2024ApJ...968L..20Y

Source Region of the Solar Wind: Statistics of the Doppler Velocities at the Chromosphere

The solar wind has been extensively studied recently with in situ observations, and the understanding of its counterpart near the solar surface has also progressed significantly. With the spectroscopic observations from the Chinese Hα Solar Explorer (CHASE), the chromospheric Dopplergram of the full solar disk is first obtained almost simultaneously. By investigating the statistics of the Doppler velocities at the chromosphere, we find that the coronal hole (CH) regions are dominated by Doppler blueshifts, with a stronger net magnetic flux region corresponding to smaller blueshift velocity. In addition to the average blueshift, the probability density of the Doppler shift is not symmetrically distributed but shows an excess at the redshift side, while the reference region does not show such an asymmetry. The redshift asymmetry may provide a possible clue for the interchange reconnection that might happen just above the chromosphere. By sampling the regions at the network boundaries in the CHs, the probability density is slightly enhanced at the parts of both larger blueshifts and redshifts compared with the result for the whole CH region. As the reference region also shows such enhancement, the crucial area associated with the origin of solar wind is not identified efficiently by sampling the overall network boundaries as demonstrated here. The present study shows the first attempt at interpreting the origin of solar wind in the transient CHs based on the CHASE spectroscopic observations, and a combination of full-disk and high-resolution observations is helpful in the future for firmly understanding the source region of solar wind.

2023ApJ...943..128S

Baryonic Effects on Lagrangian Clustering and Angular Momentum Reconstruction

Recent studies illustrate the correlation between the angular momenta of cosmic structures and their Lagrangian properties. However, only baryons are observable and it is unclear whether they reliably trace the cosmic angular momenta. We study the Lagrangian mass distribution, spin correlation, and predictability of dark matter, gas, and stellar components of galaxy-halo systems using IllustrisTNG, and show that the primordial segregations between components are typically small. Their protoshapes are also similar in terms of the statistics of moment of inertia tensors. Under the common gravitational potential they are expected to exert the same tidal torque and the strong spin correlations are not destroyed by the nonlinear evolution and complicated baryonic effects, as confirmed by the high-resolution hydrodynamic simulations. We further show that their late-time angular momenta traced by total gas, stars, or the central galaxies, can be reliably reconstructed by the initial perturbations. These results suggest that baryonic angular momenta can potentially be used in reconstructing the parameters and models related to the initial perturbations.

2022ApJ...932....3J

Non-LTE Inversion of Prominence Spectroscopic Observations in Hα and Mg II h&amp;k lines

We continued our investigation of the plasma characteristics of a quiescent prominence that occurred on 2017 March 30. The prominence was observed simultaneously by several instruments, including the Interface Region Imaging Spectrograph (IRIS) and the Multichannel Subtractive Double Pass (MSDP) spectrograph operating at the Meudon solar tower. We focused on IRIS Mg II h&amp;k and MSDP Hα spectra, selecting 55 well-coaligned points within the prominence. We computed an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence models with a non-LTE (i.e., departures from the local thermodynamic equilibrium) radiative transfer code. We then performed a 1.5D spectral inversion searching for an optimal model that best fits five parameters of the observed profiles (observables), namely, the integrated intensity of the Hα and Mg II k lines, the FWHM of both lines, and the ratio of intensities of the Mg II k and Mg II h lines. The latter is sensitive to temperature. Our results show that the prominence is a low-temperature structure, mostly below 10,000 K, with some excursions to higher values (up to 18,000 K) but also rather low temperatures (around 5000 K). The microturbulent velocity is typically low, peaking around 8 km s<SUP>-1</SUP>, and electron density values are of the order of 10<SUP>10</SUP> cm<SUP>-3</SUP>. The peak effective thickness is 500 km, although the values range up to 5000 km. The studied prominence is rather optically thin in the Hα line and optically thick in the Mg II h&amp;k lines.

2020ApJS..247...13E

Investigating Taxonomic Diversity within Asteroid Families through ATLAS Dual-band Photometry

We present here the c-o colors for identified Flora, Vesta, Nysa-Polana, Themis, and Koronis family members within the historic data set (2015-2018) of the Asteroid Terrestrial-impact Last Alert System (ATLAS). The Themis and Koronis families are known to be relatively pure C- and S-type Bus-DeMeo taxonomic families, respectively, and the extracted color data from the ATLAS broadband c- and o-filters of these two families are used to demonstrate that the ATLAS c-o color is a sufficient parameter to distinguish between the C- and S-type taxonomies. The Vesta and Nysa-Polana families are known to display a mixture of taxonomies possibly due to Vesta's differentiated parent body origin and Nysa-Polana actually consisting of two nested families with differing taxonomies. Our data show that the Flora family also displays a large degree of taxonomic mixing and the data reveal a substantial H-magnitude dependence on color. We propose and exclude several interpretations for the observed taxonomic mix. Additionally, we extract rotation periods of all of the targets reported here and find good agreement with targets that have previously reported periods.

2022RNAAS...6..175D

Plaskett's Star and Its Environment

Astrometric information from GAIA DR3 is used to examine the environment around the massive binary system Plaskett's Star (PS). PS is found to be embedded in a stellar grouping that has distinct kinematic and spatial distributions. Based on the characteristics of these neighboring stars, it is suggested that PS may have formed during the earliest phases of star formation in the neighboring cluster NGC 2244-if so, then PS likely has an age in excess of ~5 million years.

2022PASP..134j5001B

SPECULOOS Northern Observatory: Searching for Red Worlds in the Northern Skies

SPECULOOS is a ground-based transit survey consisting of six identical 1 m robotic telescopes. The immediate goal of the project is to detect temperate terrestrial planets transiting nearby ultracool dwarfs (late M-dwarf stars and brown dwarfs), which could be amenable for atmospheric research with the next generation of telescopes. Here, we report the developments of the northern counterpart of the project-SPECULOOS Northern Observatory, and present its performance during the first three years of operations from mid-2019 to mid-2022. Currently, the observatory consists of one telescope, which is named Artemis. The Artemis telescope demonstrates remarkable photometric precision, allowing it to be ready to detect new transiting terrestrial exoplanets around ultracool dwarfs. Over the period of the first three years after the installation, we observed 96 objects from the SPECULOOS target list for 6000 hr with a typical photometric precision of 0.5%, and reaching a precision of 0.2% for relatively bright non-variable targets with a typical exposure time of 25 s. Our weather downtime (clouds, high wind speed, high humidity, precipitation and/or high concentration of dust particles in the air) over the period of three years was 30% of overall night time. Our actual downtime is 40% because of additional time loss associated with technical problems.

2023RNAAS...7..255K

Pulsational Velocity Variations of the Radial Mode sdBV Star BPM 36430

Hot subdwarf B stars are core-helium burning objects that were once red giants stripped of their outer H envelopes due to binary interactions. Many exhibit pulsations that can be used to determine fundamental stellar parameters like mass and radius. High-cadence TESS photometry of the sdB star BPM 36430 revealed it to be a hybrid-mode pulsator showing several g-mode pulsations and a single strong p-mode oscillation. The latter is likely a radial mode oscillation, given its period (342 s) and high photometric amplitude (2%). Using time-series spectroscopy from the Goodman spectrograph on the 4.1 m SOAR telescope, we detect a sinusoidal radial velocity variation with a semi-amplitude of 4.4 ± 0.4 km s<SUP>-1</SUP> and period consistent with photometry of the p-mode oscillation. This detection provides further evidence the 342 s mode is radial in nature, and that the Baade-Wesselink method can be used with additional observations to constrain the stellar mass and radius.

2021ApJ...908L...6R

Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with ΛCDM

We present an expanded sample of 75 Milky Way Cepheids with Hubble Space Telescope (HST) photometry and Gaia EDR3 parallaxes, which we use to recalibrate the extragalactic distance ladder and refine the determination of the Hubble constant. All HST observations were obtained with the same instrument (WFC3) and filters (F555W, F814W, F160W) used for imaging of extragalactic Cepheids in Type Ia supernova (SN Ia) hosts. The HST observations used the WFC3 spatial scanning mode to mitigate saturation and reduce pixel-to-pixel calibration errors, reaching a mean photometric error of 5 millimags per observation. We use new Gaia EDR3 parallaxes, greatly improved since DR2, and the period-luminosity (P-L) relation of these Cepheids to simultaneously calibrate the extragalactic distance ladder and to refine the determination of the Gaia EDR3 parallax offset. The resulting geometric calibration of Cepheid luminosities has 1.0% precision, better than any alternative geometric anchor. Applied to the calibration of SNe Ia, it results in a measurement of the Hubble constant of 73.0 ± 1.4 km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, in good agreement with conclusions based on earlier Gaia data releases. We also find the slope of the Cepheid P-L relation in the Milky Way, and the metallicity dependence of its zero-point, to be in good agreement with the mean values derived from other galaxies. In combination with the best complementary sources of Cepheid calibration, we reach 1.8% precision and find H<SUB>0</SUB> = 73.2 ± 1.3 km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, a 4.2σ difference with the prediction from Planck CMB observations under ΛCDM. We expect to reach ∼1.3% precision in the near term from an expanded sample of ∼40 SNe Ia in Cepheid hosts.

2024PSJ.....5...16W

Lunar Mare Lava Flow Dynamics and Emplacement: Predictions of Non-Newtonian Flow Dynamics, Syn- and Post-emplacement Cooling and Volatile Release Patterns, and Vertical and Lateral Flow Structure Development

We apply basic principles of magma ascent from deep source regions and its eruption into a low-gravity vacuum environment to develop a theoretical treatment of the fluid dynamics and thermodynamics of mare basalt lava flow emplacement and evolution on the Moon. The vacuum conditions influenced the release of volatiles in magma passing through lava fountains, thus controlling the syn- and post-emplacement vesicularity of the resulting deposits. To explain observed lengths and volumes of Mare Imbrium-type flows, high (10<SUP>6</SUP>-10<SUP>5</SUP> m<SUP>3</SUP> s<SUP>-1</SUP>) initial magma eruption rates were needed. Combined with low lunar magma viscosity, these caused flows to be initially turbulent. Resulting high radiative heat loss and consequent high crystallization rates caused rapid non-Newtonian rheological evolution and suppression of turbulence at tens of kilometers from vents. Slower cooling rates in the subsequent laminar parts of flows imply distinctive crystal growth rate histories. In a four-phase sequence, (i) initial transient dike-tip gas release followed by (ii) Hawaiian fire fountain activity with efficient volatile loss (iii) transitioned to (iv) Strombolian explosions in a lava lake. Late-stage lava now able to retain volatiles intruded and inflated existing flow deposits after flow front advance ceased. Volatiles forced out of solution by second boiling as lava cooled caused additional inflation. Low gravity and lack of atmospheric pressure commonly produced very vesicular lava. Escape of such lava through cracks in flow crusts is a possible source of ring-moat dome structures; collapse of such lava may explain irregular mare patches.

2021ApJ...910...10H

Thermophysical Characterization of Cyclic Frost Formation in the Subsurface and Nominal Water Activity on Comets: Case Study of 67P/Churyumov-Gerasimenko

We use a generic thermophysical model to study in detail the formation of water-ice frost in the near-surface layers of comet 67P/Churyumov-Gerasimenko. We show that nightly frost formation is a common phenomenon. In particular, while abrupt landscapes may be conducive to frost formation, they are not a requisite condition. We show that the process of subsurface frost formation is similar to that of the condensed ice layer, or crust, underneath. The sublimation of frost produces regular, enhanced outgassing early in the morning. In the case of 67P, this activity is subordinate to and precedes the daily peak sourced from the ice-rich layers located above the diurnal skin depth. In any case, frost activity should be a nominal component of comet water activity.

2021ApJ...908..113H

Medium-band Observation of the Neutrino Emitting Blazar, TXS 0506+056

TXS 0506+056 is a blazar that has been recently identified as the counterpart of the neutrino event IceCube-170922A. Understanding the blazar type of TXS 0506+056 is important to constrain the neutrino emission mechanism, but the blazar nature of TXS 0506+056 is still uncertain. As an attempt to understand the nature of TXS 0506+056, we report the medium-band observation results of TXS 0506+056, covering the wavelength range of 0.575-1.025 μm. The use of the medium-band filters allows us to examine if there were any significant changes in its spectral shapes over the course of one month and give a better constraint on the peak frequency of synchrotron radiation with quasi-simultaneous data sets. The peak frequency is found to be 10<SUP>14.28</SUP> Hz, and our analysis shows that TXS 0506+056 is not an outlier from the blazar sequence. As a way to determine the blazar type, we also analyzed if TXS 0506+056 is bluer-when-brighter (BL Lac type and some flat spectrum radio quasars, FSRQs) or redder-when-brighter (found only in some FSRQs). Even though we detect no significant variability in the spectral shape larger than observational error during our medium-band observation period, the comparison with a data set taken in 2012 shows a possible redder-when-brighter behavior of FSRQs. Our results demonstrate that medium-band observations with small to moderate-sized telescopes can be an effective way to trace the spectral evolution of transients such as TXS 0506+056.

2022ApJ...937....1L

Three-dimensional Global Hybrid Simulations of Flux Transfer Event Showers at Mercury

One of the important MESSENGER observations is the formation of flux transfer event (FTE) showers, where tens of FTEs are observed in a short time interval of about 1-2 minutes, at Mercury's magnetopause. In this paper, we investigate the interactions between the solar wind and Mercury's magnetosphere using three-dimensional global hybrid simulations. When the interplanetary magnetic field (IMF) is purely southward, we can observe FTE showers at the low-latitude dayside magnetopause, and these FTEs can propagate northward or southward with a speed of about 90 km s<SUP>-1</SUP>. When the IMF is purely northward, FTE showers can be produced in both the northward and southward hemispheres of the high-latitude nightside magnetopause, and these FTEs propagate toward the magnetotail with a speed of about 250 km s<SUP>-1</SUP>. The typical FTEs have a duration of 1-2 s, and reoccur in 5-6 s. Our simulations provide a good explanation for FTE showers observed by MESSENGER.

2020PSJ.....1...81R

Exploring Trans-Neptunian Space with TESS: A Targeted Shift-stacking Search for Planet Nine and Distant TNOs in the Galactic Plane

We present results from a new pipeline custom-designed to search for faint, undiscovered solar system bodies using full-frame image data from the NASA Transiting Exoplanet Survey Satellite (TESS) mission. This pipeline removes the baseline flux of each pixel before aligning and coadding frames along plausible orbital paths of interest. We first demonstrate the performance of the pipeline by recovering the signals of three trans-Neptunian objects—90377 Sedna (V = 20.64), 2015 BP519 (V = 21.81), and 2007 TG422 (V = 22.32)—both through shift-stacking along their known sky-projected paths and through a blind recovery. We then apply this blind-search procedure in a proof-of-concept survey of TESS Sectors 18 and 19, which extend through a portion of the Galactic plane in the Northern Hemisphere. We search for dim objects at geocentric distances d = 70-800 au in a targeted search for Planet Nine and any previously unknown detached Kuiper Belt objects that may shed light on the Planet Nine hypothesis. With no input orbital information, our present pipeline can reliably recover the signals of distant solar system bodies in the Galactic plane with V &lt; 21 and current distances d ≲ 150 au, and we elaborate on paths forward to push these limits in future optimizations. The methods described in this paper will serve as a foundation for an all-sky shift-stacking survey of the distant solar system with TESS.

2022AJ....163..240M

Milliarcsecond Astrometry for the Galilean Moons Using Stellar Occultations

A stellar occultation occurs when a Solar System object passes in front of a star for an observer. This technique allows the sizes and shapes of the occulting body to be determined with kilometer precision. In addition, this technique constrains the occulting body's positions, albedos, densities, and so on. In the context of the Galilean moons, these events can provide their best ground-based astrometry, with uncertainties in the order of 1 mas (~3 km at Jupiter's distance during opposition). We organized campaigns and successfully observed a stellar occultation by Io (JI) in 2021, one by Ganymede (JIII) in 2020, and one by Europa (JII) in 2019, with stations in North and South America. We also re-analyzed two previously published events: one by Europa in 2016 and another by Ganymede in 2017. We then fit the known 3D shape of the occulting satellite and determine its center of figure. This resulted in astrometric positions with uncertainties in the milliarcsecond level. The positions obtained from these stellar occultations can be used together with dynamical models to ensure highly accurate orbits of the Galilean moons. These orbits can help when planning future space probes aiming at the Jovian system, such as JUICE by ESA and Europa Clipper by NASA. They also allow more efficient planning of flyby maneuvers.

2024ApJ...964L..14A

The NANOGrav 15 yr Data Set: Search for Transverse Polarization Modes in the Gravitational-wave Background

Recently we found compelling evidence for a gravitational-wave background with Hellings and Downs (HD) correlations in our 15 yr data set. These correlations describe gravitational waves as predicted by general relativity, which has two transverse polarization modes. However, more general metric theories of gravity can have additional polarization modes, which produce different interpulsar correlations. In this work, we search the NANOGrav 15 yr data set for evidence of a gravitational-wave background with quadrupolar HD and scalar-transverse (ST) correlations. We find that HD correlations are the best fit to the data and no significant evidence in favor of ST correlations. While Bayes factors show strong evidence for a correlated signal, the data does not strongly prefer either correlation signature, with Bayes factors ∼2 when comparing HD to ST correlations, and ∼1 for HD plus ST correlations to HD correlations alone. However, when modeled alongside HD correlations, the amplitude and spectral index posteriors for ST correlations are uninformative, with the HD process accounting for the vast majority of the total signal. Using the optimal statistic, a frequentist technique that focuses on the pulsar-pair cross-correlations, we find median signal-to-noise ratios of 5.0 for HD and 4.6 for ST correlations when fit for separately, and median signal-to-noise ratios of 3.5 for HD and 3.0 for ST correlations when fit for simultaneously. While the signal-to-noise ratios for each of the correlations are comparable, the estimated amplitude and spectral index for HD are a significantly better fit to the total signal, in agreement with our Bayesian analysis.

2020ApJS..249...29H

Mapping the Galactic Disk with the LAMOST and Gaia Red Clump Sample. I. Precise Distances, Masses, Ages, and 3D Velocities of ∼140,000 Red Clump Stars

We present a sample of ∼140,000 primary red clump (RC) stars of spectral signal-to-noise ratios higher than 20 from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Galactic spectroscopic surveys, selected based on their positions in the metallicity-dependent effective temperature-surface gravity and color-metallicity diagrams, supervised by high-quality Kepler asteroseismology data. The stellar masses and ages of those stars are further determined from the LAMOST spectra, using the kernel principal component analysis method and are trained with thousands of RCs in the LAMOST-Kepler fields with accurate asteroseismic mass measurements. The purity and completeness of our primary RC sample are generally higher than 80%. For the mass and age, a variety of tests show typical uncertainties of 15% and 30%, respectively. Using over 10,000 primary RCs with accurate distance measurements from the parallaxes of Gaia Data Release 2 (DR2), we recalibrate the K<SUB>s</SUB> absolute magnitudes of primary RCs by, for the first time, considering both the metallicity and age dependencies. With the the new calibration, distances are derived for all the primary RCs, with a typical uncertainty of 5-10%, which is even better than the values yielded by the Gaia parallax measurements for stars beyond 3-4 kpc. The sample covers a significant volume of the Galactic disk of 4 ≤ R ≤ 16 kpc, $| Z| \leqslant 5\,\mathrm{kpc}$ , and -20 ≤ φ ≤ 50°. Stellar atmospheric parameters, line-of-sight velocities, and elemental abundances derived from the LAMOST spectra and proper motions of Gaia DR2 are also provided for the sample stars. Finally, the selection function of the sample is carefully evaluated in the color-magnitude plane for different sky areas. The sample is publicly available at 10.5281/zenodo.3875974.

2020ApJ...893L..36Z

Asymmetric Lunar Magnetic Perturbations Produced by Reflected Solar Wind Particles

Magnetic perturbations characterize the solar wind interaction of the Moon. The solar wind plasma absorption on the dayside surface produces large-scale field perturbations behind, I.e., the field enhancement in the central wake and reduction on the wake boundary. The solar wind repellence over local lunar magnetic anomalies (LMAs) leads to small-scale magnetic compressions ahead. In this study, the magnetic perturbations around the Moon are examined by using the observations from a near-Moon satellite mission, the Lunar Prospector, and they exhibit a clear left-right asymmetry in a coordinate system related to the solar wind convection electric field ( ${{\boldsymbol{E}}}_{\mathrm{SW}}$ ). The magnetic field is observed to enhance before the left terminator that ${{\boldsymbol{E}}}_{\mathrm{SW}}$ points to, while on the opposite side, it is not. The test particle simulations show that ${{\boldsymbol{E}}}_{\mathrm{SW}}$ can divert the particles reflected over the LMAs to the left and then the solar wind pickup of these particles leads to the field enhancement observed before the left terminator. Behind the lunar terminator, the wake field reduction is also asymmetric. On the left, the field reduction is more remarkable and located closer to the central wake. The denser plasma, consisting of the background as well as the reflected solar wind particles, may produce a stronger diamagnetic current and thus more significant field reduction there. The asymmetric plasma and magnetic perturbations associated with the reflected particles may be a common and nonnegligible element during the solar wind interaction of a small-scale magnetic field, such as that of an asteroid or a comet.

2023ApJ...942...73X

Cosmic-CoNN: A Cosmic-Ray Detection Deep-learning Framework, Data Set, and Toolkit

Rejecting cosmic rays (CRs) is essential for the scientific interpretation of CCD-captured data, but detecting CRs in single-exposure images has remained challenging. Conventional CR detectors require experimental parameter tuning for different instruments, and recent deep-learning methods only produce instrument-specific models that suffer from performance loss on telescopes not included in the training data. We present Cosmic-CoNN, a generic CR detector deployed for 24 telescopes at the Las Cumbres Observatory, which has been made possible by the three contributions in this work: (1) We build a large and diverse ground-based CR data set leveraging thousands of images from a global telescope network. (2) We propose a novel loss function and a neural network optimized for telescope imaging data to train generic CR-detection models. At 95% recall, our model achieves a precision of 93.70% on Las Cumbres imaging data and maintains a consistent performance on new ground-based instruments never used for training. Specifically, the Cosmic-CoNN model trained on the Las Cumbres CR data set maintains high precisions of 92.03% and 96.69% on Gemini GMOS-N/S 1 × 1 and 2 × 2 binning images, respectively. (3) We build a suite of tools including an interactive CR mask visualization and editing interface, console commands, and Python APIs to make automatic, robust CR detection widely accessible by the community of astronomers. Our data set, open-source code base, and trained models are available at https://github.com/cy-xu/cosmic-conn.

2020ApJ...895L...6Z

A Fast Radio Burst Discovered in FAST Drift Scan Survey

We report the discovery of a highly dispersed fast radio burst (FRB), FRB 181123, from an analysis of ∼1500 hr of drift scan survey data taken using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulse has three distinct emission components, which vary with frequency across our 1.0-1.5 GHz observing band. We measure the peak flux density to be &gt;0.065 Jy and the corresponding fluence &gt;0.2 Jy ms. Based on the observed dispersion measure of 1812 cm<SUP>-3</SUP> pc, we infer a redshift of ∼1.9. From this, we estimate the peak luminosity and isotropic energy to be ≲2 × 10<SUP>43</SUP> erg s<SUP>-1</SUP> and ≲2 × 10<SUP>40</SUP> erg, respectively. With only one FRB from the survey detected so far, our constraints on the event rate are limited. We derive a 95% confidence lower limit for the event rate of 900 FRBs per day for FRBs with fluences &gt;0.025 Jy ms. We performed follow-up observations of the source with FAST for four hours and have not found a repeated burst. We discuss the implications of this discovery for our understanding of the physical mechanisms of FRBs.

2022ApJ...939L..31H

Has JWST Already Falsified Dark-matter-driven Galaxy Formation?

The James Webb Space Telescope (JWST) discovered several luminous high-redshift galaxy candidates with stellar masses of M <SUB>*</SUB> ≳ 10<SUP>9</SUP> M <SUB>⊙</SUB> at photometric redshifts z <SUB>phot</SUB> ≳ 10, which allows to constrain galaxy and structure formation models. For example, Adams et al. identified the candidate ID 1514 with ${\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })={9.8}_{-0.2}^{+0.2}$ located at ${z}_{\mathrm{phot}}={9.85}_{-0.12}^{+0.18}$ and Naidu et al. found even more distant candidates labeled as GL-z11 and GL-z13 with ${\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })={9.4}_{-0.3}^{+0.3}$ at ${z}_{\mathrm{phot}}={10.9}_{-0.4}^{+0.5}$ and ${\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })={9.0}_{-0.4}^{+0.3}$ at ${z}_{\mathrm{phot}}={13.1}_{-0.7}^{+0.8}$ , respectively. Assessing the computations of the IllustrisTNG (TNG50-1 and TNG100-1) and EAGLE projects, we investigate if the stellar mass buildup as predicted by the ΛCDM paradigm is consistent with these observations assuming that the early JWST calibration is correct and that the candidates are indeed located at z ≳ 10. Galaxies formed in the ΛCDM paradigm are by more than an order of magnitude less massive in stars than the observed galaxy candidates implying that the stellar mass buildup is more efficient in the early universe than predicted by the ΛCDM models. This in turn would suggest that structure formation is more enhanced at z ≳ 10 than predicted by the ΛCDM framework. We show that different star formation histories could reduce the stellar masses of the galaxy candidates alleviating the tension. Finally, we calculate the galaxy-wide initial mass function (gwIMF) of the galaxy candidates assuming the integrated galaxy IMF theory. The gwIMF becomes top-heavy for metal-poor star-forming galaxies decreasing therewith the stellar masses compared to an invariant canonical IMF.

2023ApJ...954L..20L

Observations of Twist, Current Helicity, and Writhe in the Magnetic Knots of δ-sunspots Consistent with the Kink Instability of a Highly Twisted Flux Rope

We measure current helicity (H <SUB> r </SUB> <SUP> c </SUP>) as well as proxies for twist (α <SUB> r </SUB>) and writhe (W) in the isolated magnetic knots of three delta (δ)-sunspots and report that the observations are consistent with a kink instability acting on a highly twisted flux tube. δ-spots are active regions (ARs) in which positive and negative umbrae share a penumbra. We identify and isolate "magnetic knots," i.e., opposite polarity umbrae that are in close proximity and forming the δ-configuration, in ARs NOAA 11158, 11267, and 11476 as observed with data from the Solar Dynamic Observatory Helioseismic and Magnetic Imager. We find that H <SUB> r </SUB> <SUP> c </SUP>, α <SUB> r </SUB>, and W have the same sign for each magnetic knot, as predicted in simulations of a kink instability acting on highly twisted flux tubes. The deformed flux tube causing the δ-formation, the magnetic knot, is only a portion of the entire AR and demonstrates the potential for the kink instability to act on a smaller spatial scale within the AR. Each magnetic footpoint contains a single sign of the radial current, J <SUB> r </SUB>, which suggests that we are observing the core of the flux rope without return currents. As a counterexample, we analyze one β-spot that shows H <SUB> r </SUB> <SUP> c </SUP> and α <SUB> r </SUB> have the opposite signs of W. While our observations support the formation mechanism of the magnetic knots in δ-spots being the kink instability, a much larger sample is needed to determine confidently the prevalence of the kink instability as the cause of flux tube deformation.

2021PSJ.....2...50A

Formation Conditions of Titan's and Enceladus's Building Blocks in Saturn's Circumplanetary Disk

The building blocks of Titan and Enceladus are believed to have formed in a late-stage circumplanetary disk (CPD) around Saturn. Evaluating the evolution of the abundances of volatile species in this disk as a function of the migration, growth, and evaporation of icy grains is then of primary importance to assess the origin of the material that eventually formed these two moons. Here we use a simple prescription of Saturn's CPD in which the location of the centrifugal radius is varied, to investigate the time evolution of the icelines of water ice, ammonia hydrate, methane clathrate, carbon monoxide, and dinitrogen pure condensates. To match their compositional data, the building blocks of both moons would have had to form in a region of the CPD situated between the icelines of carbon monoxide and dinitrogen at their outer limit, and the iceline of methane clathrate as their inner limit. We find that a source of dust at the location of centrifugal radius does not guarantee the replenishment of the disk in the volatiles assumed to be primordial in Titan and Enceladus. Only simulations assuming a centrifugal radius in the range 66-100 Saturnian radii allow for the formation and growth of solids with compositions consistent with those measured in Enceladus and Titan. The species are then able to evolve in solid forms in the system for longer periods of time, even reaching an equilibrium, thus favoring the formation of Titan and Enceladus's building blocks in this region of the disk.

2022ApJ...940L...3W

The Dark Matter Tidal Stripping History of the Sagittarius Core with N-body Simulations

The infall of the Sagittarius (Sgr) dwarf spheroidal galaxy in the Milky Way halo is an unique opportunity to understand how the different components of a dwarf galaxy could be tidally removed. In this work, we reconstruct the Sgr core morphology and kinematics on the basis of a model that has already successfully reproduced the Sgr stream. Here we use a very high resolution model that almost resolves individual stars in the Sgr core. It reproduces most of the observed morphology and kinematic properties, without specific fine tuning. We also show that the dark matter may have been almost entirely stripped by Milky Way tides after two passages at the pericenter. Finally the model predicts that the Sgr core will be fully disrupted within the next 2 Gyr.

2024ApJS..270...22W

GeV Variability Properties of TeV Blazars Detected by Fermi-LAT

Variability is a prominent observational feature of blazars. The high-energy radiation mechanism of jets has always been important but is still unclear. In this work, we performed a detailed analysis using Fermi-LAT data across 15 yr and obtained GeV light-curve information for 78 TeV blazars detected by Fermi. We provided annual GeV fluxes and corresponding spectral indices for the 78 TeV blazars and thorough monthly GeV fluxes for a subsample of 41 bright blazars. Our results suggest a strong correlation between the γ-ray photon index and $\mathrm{log}{L}_{\gamma }$ for the flat spectrum radio quasars (FSRQs) and high-energy peaked BL Lacs. Fourteen sources in our sample show significant GeV outbursts/flares above the relatively stable, low-flux light curve, with six of them showing a clear sharp peak profile in their 5 day binned light curves. We quantified the variability utilizing the fractional variability parameter F <SUB>var</SUB>, and found that the flux of the FSRQs showed significantly stronger variability than that of the BL Lacs. The 41 bright blazars in this work are best fit by a log-normal flux distribution. We checked the spectral behavior and found 11 out of the 14 sources show a bluer-when-brighter trend, suggesting this spectral behavior for these TeV blazars at the GeV band arises from the mechanism in which the synchrotron-self Compton process dominates the GeV emission. Our research offers a systematic analysis of the GeV variability properties of TeV blazars and serves as a helpful resource for further associated blazar studies.

2024PSJ.....5..128K

Impact Disruption of Bjurböle Porous Chondritic Projectile

The ∼200 m s<SUP>‑1</SUP> impact of a single 400 kg Bjurböle L/LL ordinary chondrite meteorite onto sea ice resulted in the catastrophic disruption of the projectile. This resulted in a significant fraction of decimeter-sized fragments that exhibit power-law cumulative size and mass distributions. This size range is underrepresented in impact experiments and asteroid boulder studies. The Bjurböle projectile fragments share similarities in shape (sphericity and roughness at small and large scales) with asteroid boulders. However, the mean aspect ratio (3D measurement) and apparent aspect ratio (2D measurement) of the Bjurböle fragments is 0.83 and 0.77, respectively, indicating that Bjurböle fragments are more equidimensional compared to both fragments produced in smaller-scale impact experiments and asteroid boulders. These differences may be attributed either to the fragment source (projectile versus target), to the high porosity and low strength of Bjurböle, to the lower impact velocity compared with typical asteroid collision velocities, or potentially to fragment erosion during sea sediment penetration or cleaning.

2022ApJ...931..136Z

Li-rich Giants in LAMOST Survey. III. The Statistical Analysis of Li-rich Giants

The puzzle of the Li-rich giant is still unsolved, contradicting the prediction of the standard stellar models. Although the exact evolutionary stages play a key role in the knowledge of Li-rich giants, a limited number of Li-rich giants have been observed with high-quality asteroseismic parameters to clearly distinguish the stellar evolutionary stages. Based on the LAMOST Data Release 7 (DR7), we applied a data-driven neural network method to derive the parameters for giant stars, which contain the largest number of Li-rich giants. The red giant stars are classified into three stages of Red Giant Branch (RGB), Primary Red Clump (PRC), and Secondary Red Clump (SRC) relying on the estimated asteroseismic parameters. In the statistical analysis of the properties (i.e., stellar mass, carbon, nitrogen, Li-rich distribution, and frequency) of Li-rich giants, we found that (1) most of the Li-rich RGB stars are suggested to be the descendants of Li-rich pre-RGB stars and/or the result of engulfment of planet or substellar companions; (2) the massive Li-rich SRC stars could be the natural consequence of Li depletion from the high-mass Li-rich RGB stars; and (3) internal mixing processes near the helium flash can account for the phenomenon of Li richness on PRC that dominated the Li-rich giants. Based on the comparison of [C/N] distributions between Li-rich and normal PRC stars, the Li-enriched processes probably depend on the stellar mass.

2021ApJ...918...28C

Eclipsing Binaries Found by the EREBOS Project: Gaia DR2 6097540197980557440-a Deeply Eclipsing sdB+dM System

We present time-series spectroscopy and photometry of Gaia DR2 6097540197980557440, a new deeply eclipsing hot subdwarf B (sdB) + M dwarf (dM) binary. We discovered this object during the course of the Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project, which aims to find new eclipsing sdB+dM binaries (HW Vir systems) and increase the small sample of studied systems. In addition to the primary eclipse, which is in excess of ~5 mag in the optical, the light curve also shows features typical for other HW Vir binaries such as a secondary eclipse and strong reflection effect from the irradiated, cool companion. The orbital period is 0.127037 days (~3 hr), falling right at the peak of the orbital period distribution of known HW Vir systems. Analysis of our time-series spectroscopy yields a radial velocity semiamplitude of K<SUB>sdB</SUB> = 100.0 ± 2.0 km s<SUP>-1</SUP>, which is among the fastest line-of-sight velocities found to date for an HW Vir binary. State-of-the-art atmospheric models that account for deviations from local thermodynamic equilibrium are used to determine the atmospheric parameters of the sdB. Although we cannot claim a unique light-curve modeling solution, the best-fitting model has an sdB mass of M<SUB>sdB</SUB> = 0.47 ± 0.03 M<SUB>⊙</SUB> and a companion mass of M<SUB>dM</SUB> = 0.18 ± 0.01 M<SUB>⊙</SUB>. The radius of the companion appears to be inflated relative to theoretical mass-radius relationships, consistent with other known HW Vir binaries. Additionally, the M dwarf is one of the most massive found to date among this type of binary.

2024ApJ...960...74S

High-energy Neutrinos from Gamma-Ray-faint Accretion-powered Hypernebulae

Hypernebulae are inflated by accretion-powered winds accompanying hyper-Eddington mass transfer from an evolved post-main-sequence star onto a black hole or neutron star companion. The ions accelerated at the termination shock-where the collimated fast disk winds and/or jet collide with the slower, wide-angled wind-fed shell-can generate high-energy neutrinos via hadronic proton-proton reactions, and photohadronic (p γ) interactions with the disk thermal and Comptonized nonthermal background photons. It has been suggested that some fast radio bursts (FRBs) may be powered by such short-lived jetted hyper-accreting engines. Although neutrino emission associated with the millisecond duration bursts themselves is challenging to detect, the persistent radio counterparts of some FRB sources-if associated with hypernebulae-could contribute to the high-energy neutrino diffuse background flux. If the hypernebula birth rate follows that of stellar-merger transients and common envelope events, we find that their volume-integrated neutrino emission-depending on the population-averaged mass-transfer rates-could explain up to ~25% of the high-energy diffuse neutrino flux observed by the IceCube Observatory and the Baikal Gigaton Volume Detector Telescope. The time-averaged neutrino spectrum from hypernebula-depending on the population parameters-can also reproduce the observed diffuse neutrino spectrum. The neutrino emission could in some cases furthermore extend to &gt;100 PeV, detectable by future ultra-high-energy neutrino observatories. The large optical depth through the nebula to Breit-Wheeler (γ γ) interaction attenuates the escape of GeV-PeV gamma rays coproduced with the neutrinos, rendering these gamma-ray-faint neutrino sources, consistent with the Fermi observations of the isotropic gamma-ray background.

2022ApJ...934...49G

A Candle in the Wind: A Radio Filament in the Core of the A3562 Galaxy Cluster

Using a MeerKAT observation of the galaxy cluster A3562 (a member of the Shapley supercluster), we have discovered a narrow, long and straight, very faint radio filament, which branches out at a straight angle from the tail of a radio galaxy located in projection near the core of the cluster. The radio filament spans 200 kpc and aligns with a sloshing cold front seen in the X-rays, staying inside the front in projection. The radio spectral index along the filament appears uniform (within large uncertainties) at α ≃ -1.5. We propose that the radio galaxy is located outside the cold front but dips its tail under the front. The tangential wind that blows there may stretch the radio plasma from the radio galaxy into a filamentary structure. Some reacceleration is needed in this scenario to keep the radio spectrum uniform. Alternatively, the cosmic-ray electrons from that spot in the tail can spread along the cluster magnetic field lines, straightened by that same tangential flow, via anomalously fast diffusion. Our radio filament can provide constraints on this process. We also uncover a compact radio source at the brightest cluster galaxy that is 2-3 orders of magnitude less luminous than those in typical cluster central galaxies-probably an example of a brightest cluster galaxy starved of accretion fuel by gas sloshing.

2021ApJ...921..104C

Testing the Strong Equivalence Principle. II. Relating the External Field Effect in Galaxy Rotation Curves to the Large-scale Structure of the Universe

Theories of modified gravity generically violate the strong equivalence principle, so that the internal dynamics of a self-gravitating system in freefall depends on the strength of the external gravitational field (the external field effect). We fit rotation curves (RCs) from the SPARC database with a model inspired by Milgromian dynamics (MOND), which relates the outer shape of an RC to the external Newtonian field from the large-scale baryonic matter distribution through a dimensionless parameter e<SUB>N</SUB>. We obtain a &gt; 4σ statistical detection of the external field effect (i.e. e<SUB>N</SUB> &gt; 0 on average), confirming previous results. We then locate the SPARC galaxies in the cosmic web of the nearby universe and find a striking contrast in the fitted e<SUB>N</SUB> values for galaxies in underdense versus overdense regions. Galaxies in an underdense region between 22 and 45 Mpc from the celestial axis in the northern sky have RC fits consistent with e<SUB>N</SUB> ≃ 0, while those in overdense regions adjacent to the CfA2 Great Wall and the Perseus-Pisces Supercluster return e<SUB>N</SUB> that are a factor of two larger than the median for SPARC galaxies. We also calculate independent estimates of e<SUB>N</SUB> from galaxy survey data and find that they agree with the e<SUB>N</SUB> inferred from the RCs within the uncertainties, the chief uncertainty being the spatial distribution of baryons not contained in galaxies or clusters.

2020ApJ...895..138K

New Type Ia Supernova Yields and the Manganese and Nickel Problems in the Milky Way and Dwarf Spheroidal Galaxies

In our quest to identify the progenitors of Type Ia supernovae (SNe Ia), we first update the nucleosynthesis yields for both near-Chandrasekhar- (Ch) and sub-Ch-mass white dwarfs (WDs) for a wide range of metallicities with our 2D hydrodynamical code and the latest nuclear reaction rates. We then include the yields in our galactic chemical evolution code to predict the evolution of elemental abundances in the solar neighborhood and dwarf spheroidal (dSph) galaxies Fornax, Sculptor, Sextans, and Carina. In the observations of the solar neighborhood stars, Mn shows an opposite trend to α elements, showing an increase toward higher metallicities, which is very well reproduced by the deflagration-detonation transition of Ch-mass WDs but never by double detonations of sub-Ch-mass WDs alone. The problem of Ch-mass SNe Ia was the Ni overproduction at high metallicities. However, we found that Ni yields of Ch-mass SNe Ia are much lower with the solar-scaled initial composition than in previous works, which keeps the predicted Ni abundance within the observational scatter. From the evolutionary trends of elemental abundances in the solar neighborhood, we conclude that the contribution of sub-Ch-mass SNe Ia to chemical enrichment is up to 25%. In dSph galaxies, however, larger enrichment from sub-Ch-mass SNe Ia than in the solar neighborhood may be required, which causes a decrease in [(Mg, Cr, Mn, Ni)/Fe] at lower metallicities. The observed high [Mn/Fe] ratios in Sculptor and Carina may also require additional enrichment from pure deflagrations, possibly as SNe Iax. Future observations of dSph stars will provide more stringent constraints on the progenitor systems and explosion mechanism of SNe Ia.

2021ApJ...908..148H

Identifying and Repairing Catastrophic Errors in Galaxy Properties Using Dimensionality Reduction

Our understanding of galaxy evolution is derived from large surveys designed to maximize efficiency by only observing the minimum amount needed to infer properties for a typical galaxy. However, for a few percent of galaxies in every survey, these observations are insufficient and derived properties can be catastrophically wrong. Further, it is currently difficult or impossible to determine which objects have failed, so that these contaminate every study of galaxy properties. We develop a novel method to identify these objects by combining the astronomical codes that infer galaxy properties with the dimensionality reduction algorithm t-SNE, which groups similar objects to determine which inferred properties are out of place. This method provides an improvement for the COSMOS catalog, which already uses existing techniques for catastrophic error removal, and therefore should improve the quality of large catalogs and any studies that are sensitive to large redshift errors.

2024ApJ...965L..17S

Discovery of the Longest-period Classical Cepheid in the Milky Way

We report the discovery of the classical Cepheid OGLE-GD-CEP-1884 (= GDS_J1535467-555656) with the longest pulsation period known in our Galaxy. The period of 78.14 days is nearly 10 days longer than that of the previous record-holding Cepheid, S Vulpeculae, and thus, OGLE-GD-CEP-1884 can be categorized as the first ultra-long-period Cepheid in the Milky Way. This star is present in the ASAS-SN and Gaia DR3 catalogs of variable stars, but it has been classified as a long-period variable in those catalogs. Based on more than 10 yr of the photometric monitoring of this star carried out by the OGLE project in the I and V bands and a radial velocity curve from the Gaia Focused Product Release, we unequivocally demonstrate that this object is a fundamental-mode classical Cepheid. By employing the mid-infrared period–luminosity relation, we determine the distance to OGLE-GD-CEP-1884 (4.47 ± 0.34 kpc) and place it on the Milky Way map, along with about 2400 other classical Cepheids. We also discuss the potential of finding additional ultra-long-period Cepheids in our Galaxy.

2022RNAAS...6...79L

Long-term Stability of Six Neptunian Trojans

This paper explores the long-term stability of six Neptunian Trojans. In contrast with other Neptunian Trojans, these objects have previously unknown lifetimes and larger orbital uncertainties due to their shorter observational arcs. We obtained new astrometry of the six Trojans using the Magellan telescope, refit their orbits, and performed Gyr-long numerical integrations to estimate their lifetimes. The results show that five of these six objects are stable over Gyr timescales. The remaining object, 2015 VV<SUB>165</SUB>, has a calculated lifetime of 0.691 ± 0.001 Gyr, which is similar to the previous estimate of 0.65 Gyr. As a result, the shorter lifetime of this latter object is most likely physical (rather than due to uncertainties in its orbital determination).

2020ApJ...905..135B

The Global Stability of M33 in MOND

The dynamical stability of disk galaxies is sensitive to whether their anomalous rotation curves are caused by dark matter halos or Milgromian dynamics (MOND). We investigate this by setting up a MOND model of M33. We first simulate it in isolation for 6 Gyr, starting from an initial good match to the rotation curve (RC). Too large a bar and bulge form when the gas is too hot, but this is avoided by reducing the gas temperature. A strong bar still forms in 1 Gyr, but rapidly weakens and becomes consistent with the observed weak bar. Previous work showed this to be challenging in Newtonian models with a live dark matter halo, which developed strong bars. The bar pattern speed implies a realistic corotation radius of 3 kpc. However, the RC still rises too steeply, and the central line-of-sight velocity dispersion (LOSVD) is too high. We then add a constant external acceleration field of 8.4 × 10<SUP>-12</SUP> m s<SUP>-2</SUP> at 30° to the disk as a first-order estimate for the gravity exerted by M31. This suppresses buildup of material at the center, causing the RC to rise more slowly and reducing the central LOSVD. Overall, this simulation bears good resemblance to several global properties of M33, and highlights the importance of including even a weak external field on the stability and evolution of disk galaxies. Further simulations with a time-varying external field, modeling the full orbit of M33, will be needed to confirm its resemblance to observations.

2022ApJ...940L..23A

A First Look at the Abundance Pattern-O/H, C/O, and Ne/O-in z &gt; 7 Galaxies with JWST/NIRSpec

We analyze the rest-frame near-UV and optical nebular spectra of three z &gt; 7 galaxies from the Early Release Observations taken with the Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST). These three high-z galaxies show the detection of several strong emission nebular lines, including the temperature-sensitive [O III] λ4363 line, allowing us to directly determine the nebular conditions and abundances for O/H, C/O, and Ne/O. We derive O/H abundances and ionization parameters that are generally consistent with other recent analyses. We analyze the mass-metallicity relationship (i.e., slope) and its redshift evolution by comparing between the three z &gt; 7 galaxies and local star-forming galaxies. We also detect the C III] λλ1907, 1909 emission in a z &gt; 8 galaxy from which we determine the most distant C/O abundance to date. This valuable detection of log(C/O) = -0.83 ± 0.38 provides the first test of C/O redshift evolution out to high redshift. For neon, we use the high-ionization [Ne III] λ3869 line to measure the first Ne/O abundances at z &gt; 7, finding no evolution in this α-element ratio. We explore the tentative detection of [Fe II] and [Fe III] lines in a z &gt; 8 galaxy, which would indicate a rapid buildup of metals. Importantly, we demonstrate that properly flux-calibrated and higher-S/N spectra are crucial to robustly determine the abundance pattern in z &gt; 7 galaxies with NIRSpec/JWST.

2021AJ....161..272H

A Stellar Activity F-statistic for Exoplanet Surveys (SAFE)

In the search for planets orbiting distant stars, the presence of stellar activity in the atmospheres of observed stars can obscure the radial velocity signal used to detect such planets. Furthermore, this stellar activity contamination is set by the star itself and cannot simply be avoided with better instrumentation. Various stellar activity indicators have been developed that may correlate with this contamination. We introduce a new stellar activity indicator called the Stellar Activity F-statistic for Exoplanet surveys (SAFE) that has higher statistical power (i.e., probability of detecting a true stellar activity signal) than many traditional stellar activity indicators in a simulation study of an active region on a Sun-like star with a moderate-to-high signal-to-noise ratio. Also through simulation, the SAFE is demonstrated to be associated with the projected area on the visible side of the star covered by active regions. We also demonstrate that the SAFE detects statistically significant stellar activity in most of the spectra for HD 22049, a star known to have high stellar variability. Additionally, the SAFE is calculated for recent observations of the three low-variability stars HD 34411, HD 10700, and HD 3651, the latter of which is known to have a planetary companion. As expected, the SAFE for these three only occasionally detects activity. Furthermore, initial exploration appears to indicate that the SAFE may be useful for disentangling stellar activity signals from planet-induced Doppler shifts.

2020ApJ...896...59A

Neon Abundances of B Stars in the Solar Neighborhood

We constructed a comprehensive model atom for Ne I-Ne II using the most-up-to-date atomic data available and evaluated the nonlocal thermodynamic equilibrium (NLTE) line formation for Ne I and Ne II in classical 1D models representing the atmospheres of B-type stars. We find that the large NLTE strengthening of the Ne I lines corresponding to the 2p<SUP>5</SUP>3p-2p<SUP>5</SUP>3s transition array occurs due to extremely small photoionization cross sections of the 2p<SUP>5</SUP>3s levels that lead to strong overpopulation of these levels relative to their LTE populations. The deviations from LTE for most Ne II lines are small and do not exceed 0.11 dex in absolute value. We analyzed 20 lines of Ne I and 13 lines of Ne II for 24 B-type stars in the temperature range of 10,400 ≤ ${T}_{\mathrm{eff}}$ ≤ 33,400 K. For five stars, the NLTE leads to consistent abundances of Ne I and Ne II, while the difference in LTE abundance can reach up to 0.50 dex. Using the experimental oscillator strengths recently measured by Piracha et al. leads to smaller line-by-line scatter for most of the investigated stars. The average neon abundance in 24 B-type stars in the solar neighborhood is 8.02 ± 0.05. This value may provide indirect constraints on the solar photospheric neon abundance.

2020ApJ...898...23L

The Impact of Type Ia Supernovae in Quiescent Galaxies. II. Energetics and Turbulence

Type Ia supernovae (SNe Ia) provide unique and important feedback in quiescent galaxies, but their impact has been underappreciated. In this paper, we analyze a series of high-resolution simulations to examine the energetics and turbulence of the medium under SNe Ia. We find that when SN remnants are resolved, their effects differ distinctly from a volumetric heating term, as is commonly assumed in unresolved simulations. First, the net heating is significantly higher than expected, by 30 ± 10% per cooling time. This is because a large fraction of the medium is pushed into lower densities, which cool inefficiently. Second, the medium is turbulent; the root-mean-squared (rms) velocity of the gas to 20-50 km s<SUP>-1</SUP> on a driving scale of tens of parsecs. The velocity field of the medium is dominated by compressional modes, which are larger than the solenoidal components by a factor of 3-7. Third, the hot gas has a very broad density distribution. The ratio between the density fluctuations and the rms Mach number, parameterized as b, is 2-20. This is in contrast to previous simulations of turbulent media, which have found b ≲ 1. The difference is mainly caused by the localized heating of SNe Ia, which creates a large density contrast. Last, the typical length scale of a density fluctuation grows with time, forming increasingly larger bubbles and filamentary ridges. These underlying density fluctuations need to be included when X-ray observations are interpreted.

2021AJ....162..146S

A Gaia-based Photometric and Kinematic Analysis of the Old Open Cluster King 11

This paper presents an investigation of an old age open cluster King 11 using Gaia's Early Data Release 3 data. Considering the stars with membership probability (P<SUB>μ</SUB>) &gt; 90%, we identified 676 most probable cluster members within the cluster's limiting radius. The mean proper motion for King 11 is determined as: μ<SUB>x</SUB> = - 3.391 ± 0.006 and μ<SUB>y</SUB> = - 0.660 ± 0.004 mas yr<SUP>-1</SUP>. The blue straggler stars of King 11 show a centrally concentrated radial distribution. The values of limiting radius, age, and distance are determined as 18'51, 3.63 ± 0.42 Gyr, and 3.33 ± 0.15 kpc, respectively. The cluster's apex coordinates (A = 267°84 ± 1°01, D = - 27°48 ± 1°03) are determined using the apex diagram method and verified using the (μ<SUB>U</SUB>, μ<SUB>T</SUB>) diagram. We also obtained the orbit that the cluster follows in the Galaxy and estimated its tentative birthplace in the disk. The resulting spatial velocity of King 11 is 60.2 ± 2.16 km s<SUP>-1</SUP>. A significant oscillation along the Z coordinate up to 0.556 ± 0.022 kpc is determined.

2024ApJ...965...19M

Probing Dark Energy and Modifications of Gravity with Ground-based millimeter-wavelength Line Intensity Mapping

Line intensity mapping (LIM) can provide a powerful means to constrain the theory of gravity and the nature of dark energy at low and high redshifts by mapping the large-scale structure over many redshift epochs. In this paper, we investigate the potential of the next generation ground-based millimeter-wavelength LIM surveys in constraining several models beyond ΛCDM, involving either a dynamic dark energy component or modifications of the theory of gravity. Limiting ourselves to two-point clustering statistics, we consider the measurements of auto-spectra of several CO rotational lines (from J = 2‑1 to J = 6‑5) and the [C II] fine structure line in the redshift range of 0.25 &lt; z &lt; 12. We consider different models beyond ΛCDM, each one with different signatures and peculiarities. Among them, we focus on Jordan–Brans–Dicke and axion-driven early dark energy models as examples of well-studied scalar-tensor theories acting at late and early times, respectively. Additionally, we consider three phenomenological models based on an effective description of gravity at cosmological scales. We show that LIM surveys deployable within a decade (with ∼10<SUP>8</SUP> spectrometer hours) have the potential to improve upon the current bounds on all considered models significantly. The level of improvements range from a factor of a few to an order of magnitude.

2023RNAAS...7...68L

An Estimate of the Distance to AN Ser using an RR Lyrae Period-Luminosity Relationship

The relationship between the period of a Cepheid variable star and its absolute magnitude-the Period-Luminosity, or Leavitt Law-can be used with a measurement of apparent magnitude to measure the star's distance. RR Lyrae stars are evolved low-mass stars with shorter periods and lower luminosities than Cepheids, but they are particularly useful for estimating distances to the oldest stellar clusters. We observed the brightness of an RR Lyrae star over time using the robotic telescopes of Las Cumbres Observatory to determine its period and apparent magnitude in four bands. We used that information and theoretical period-luminosity relationships for RR Lyrae stars to determine the distance to AN Ser to be 876 ± 25 pc. Our measured distance is smaller than that modeled by GAIA DR3 via stellar parallax, BP/RP spectra, and G-band photometry (959 pc).

2023AJ....166..169H

Most Rotational Variables Dominated by a Single Bright Feature Are α <SUP>2</SUP> CVn Stars

We previously reported a rare class of variable star light curves isolated from a sample of 4.7 million candidate variables from the ATLAS survey. Dubbed "UCBH" light curves, they have broad minima and narrow, symmetrical maxima, with typical periods of 1-10 days and amplitudes of 0.05-0.20 mag. They maintain constant amplitude, shape, and phase coherence over multiple years but do not match any known class of pulsating variables. A localized bright spot near the equator of a rotating star will produce a UCBH-type light curve for most viewing geometries. Most stars that exhibit rotational variability caused primarily by a single bright feature should therefore appear as UCBH stars, although a rotating bright spot is not the only thing that could produce a UCBH-type light curve. We have spectroscopically investigated 14 UCBH stars and found 10 of them to be Ap/Bp stars: A-type or B-type stars with greatly enhanced photospheric abundances of specific heavy elements. Rotationally variable Ap/Bp stars are referred to as α <SUP>2</SUP> CVn variables. Most ATLAS UCBH stars are therefore α <SUP>2</SUP> CVn stars, although only a minority of α <SUP>2</SUP> CVn stars in the literature have UCBH light curves. The fact that α <SUP>2</SUP> CVn stars dominate the UCBH class suggests that lone bright spots with sufficient size and contrast develop more readily on Ap/Bp stars than on any other type. The α <SUP>2</SUP> CVn UCBH stars may be characterized by a specific magnetic field topology, making them intriguing targets for future Zeeman-Doppler imaging.

2020ApJ...896..153F

ACRONYM IV: Three New, Young, Low-mass Spectroscopic Binaries

As part of our search for new low-mass members of nearby young moving groups (YMGs), we discovered three low-mass, spectroscopic binaries, two of which are not kinematically associated with any known YMG. Using high-resolution optical spectroscopy, we measure the component and systemic radial velocities of the systems, as well as their lithium absorption and Hα emission, both spectroscopic indicators of youth. One system (2MASS J02543316-5108313, M2.0+M3.0) we confirm as a member of the 40 Myr old Tuc-Hor moving group, but whose binarity was previously undetected. The second young binary (2MASS J08355977-3042306, K5.5+M1.5) is not a kinematic match to any known YMG, but each component exhibits lithium absorption and strong and wide Hα emission indicative of active accretion, setting an upper age limit of 15 Myr. The third system (2MASS J10260210-4105537, M1.0+M3.0) has been hypothesized in the literature to be a member of the 10 Myr old TW Hya Association, but our measured systemic velocity shows the binary is in fact not part of any known YMG. This last system also has lithium absorption in each component, and has strong and variable Hα emission, setting an upper age limit of 15 Myr based on the lithium detection.

2023RNAAS...7..104M

The Behavior of Bp Si Stars in the far-UV-Paper VI: HD 215441

The analysis of spectra of the B9 Si star HD 215441 recorded by the SWP camera on board the International Ultraviolet Explorer reveals large amplitude variations of the far-ultraviolet spectral energy distribution over a time interval of about half the rotation period. In contrast, the level of the mid-UV flux does not vary between phases of FUV flux maximum and minimum which suggests that changes of the silicon continuous and line opacity play an important role in the variations. The optical brightness recorded by the Fine Error Sensor on board IUE is anticorrelated with the FUV flux, reflecting the redistribution of the FUV flux towards longer wavelengths.

2022PASP..134l3001R

Techniques for Measuring Parallax and Proper Motion with VLBI

Astrometry at centimeter wavelengths using Very Long Baseline Interferometry is approaching accuracies of ~1 μas for the angle between a target and a calibrator source separated by ≲1° on the sky. The BeSSeL Survey and the Japanese VERA project are using this to map the spiral structure of the Milky Way by measuring trigonometric parallaxes of hundreds of maser sources associated with massive, young stars. This paper outlines how μas astrometry is done, including details regarding the scheduling of observations, calibration of data, and measuring positions.

2024ApJ...966..112S

Analysis of BMR Tilt from AutoTAB Catalog: Hinting toward the Thin Flux Tube Model?

One of the intriguing mechanisms of the Sun is the formation of bipolar magnetic regions (BMRs) in the solar convection zone (CZ), which are observed as regions of concentrated magnetic fields of opposite polarity on the photosphere. These BMRs are tilted with respect to the equatorial line, which statistically increases with latitude. The thin flux tube model, employing the rise of magnetically buoyant flux loops and their twist by Coriolis force, is a popular paradigm for explaining the formation of tilted BMRs. In this study, we assess the validity of the thin flux tube model by analyzing the tracked BMR data obtained through the Automatic Tracking Algorithm for BMRs. Our observations reveal that the tracked BMRs exhibit the expected collective behaviors. We find that the polarity separation of BMRs increases over their normalized lifetime, supporting the assumption of a rising flux tube from the CZ. Moreover, we observe an increasing trend of the tilt with the flux of the BMR, suggesting that rising flux tubes associated with lower flux regions are primarily influenced by drag force and Coriolis force, while in higher flux regions, magnetic buoyancy dominates. Furthermore, we observe Joy's law dependence for emerging BMRs from their first detection, indicating that at least a portion of the tilt observed in BMRs can be attributed to the Coriolis force. Notably, lower flux regions exhibit a higher amount of fluctuations associated with their tilt measurement compared to stronger flux regions, suggesting that lower flux regions are more susceptible to turbulent convection.

2020ApJ...897...74Z

G15.684-0.29: One of the Largest Galactic Infrared Bubbles Showing Strong Evidence of Triggered Star Formation

The bubble G15.684-0.29 has a radius of 15.7 pc. Its large size indicates that it may have enough time to trigger star formation. We identify 39 dense cold clumps around the bubble from the Hi-GAL survey. All of them satisfy the criteria for forming massive stars, and most of them lie in the bubble shell. We identify 19 molecular clumps around the bubble from the <SUP>12</SUP>CO(3-2) survey, all of which are gravitationally bound. We found 9 Class I YSOs, 28 Class II YSOs, and 12 transition disks (TDs) around the bubble. For those young stellar objects (YSOs) located within the bubble boundary, 6 of 7 Class I YSOs lie in the shell, 15 of 22 Class II YSOs lie inside the bubble, and 3 of 5 TDs lie inside the bubble. The dynamical age of G15.684-0.29 in a turbulent medium is ∼4 Myr, which is much greater than the shell fragmentation time, ∼0.82-1.74 Myr. We suggest that triggered star formation may be ongoing in the shell of the bubble, and the collect and collapse model may work here. However, we cannot rule out the possibility that the radiation-driven implosion model may work on the formation of some YSOs. As we expected, the larger bubble has a much longer dynamical age, but we failed to find a clear age gradient for YSOs around the bubble.

2022AJ....164..195F

DELIGHT: Deep Learning Identification of Galaxy Hosts of Transients using Multiresolution Images

We present DELIGHT, or Deep Learning Identification of Galaxy Hosts of Transients, a new algorithm designed to automatically and in real time identify the host galaxies of extragalactic transients. The proposed algorithm receives as input compact, multiresolution images centered at the position of a transient candidate and outputs two-dimensional offset vectors that connect the transient with the center of its predicted host. The multiresolution input consists of a set of images with the same number of pixels, but with progressively larger pixel sizes and fields of view. A sample of 16,791 galaxies visually identified by the Automatic Learning for the Rapid Classification of Events broker team was used to train a convolutional neural network regression model. We show that this method is able to correctly identify both relatively large (10″ &lt; r &lt; 60″) and small (r ≤ 10″) apparent size host galaxies using much less information (32 kB) than with a large, single-resolution image (920 kB). The proposed method has fewer catastrophic errors in recovering the position and is more complete and has less contamination (&lt;0.86%) recovering the crossmatched redshift than other state-of-the-art methods. The more efficient representation provided by multiresolution input images could allow for the identification of transient host galaxies in real time, if adopted in alert streams from new generation of large -etendue telescopes such as the Vera C. Rubin Observatory.

2024ApJ...961...33Y

A Pathway for Collisional Planetesimal Growth in the Ice-dominant Regions of Protoplanetary Disks

We present a semi-analytic model for the growth, drift, desorption, and fragmentation of millimeter- to meter-sized particles in protoplanetary disks. Fragmentation occurs where particle collision velocities exceed critical fragmentation velocities. Using this criterion, we produce fragmentation regions in disk orbital radius-particle size phase space for particles with a range of material properties, structures, and compositions (including SiO<SUB>2</SUB>, Mg<SUB>2</SUB>SiO<SUB>4</SUB>, H<SUB>2</SUB>O, CO<SUB>2</SUB>, and CO). For reasonable disk conditions, compact aggregate H<SUB>2</SUB>O, CO<SUB>2</SUB>, and CO ice particles do not reach destructive relative velocities and are thus not likely to undergo collisional fragmentation. Uncoated silicate particles are more susceptible to collisional destruction and are expected to fragment in the inner disk, consistent with previous work. We then calculate the growth, drift, and sublimation of small particles, initially located in the outer disk. We find that ice-coated particles can avoid fragmentation as they grow and drift inward under a substantial range of disk conditions, as long as the particles are aggregates composed of 0.1 μm-sized monomers. Such particles may undergo runaway growth in disk regions abundant in H<SUB>2</SUB>O or CO<SUB>2</SUB> ice, depending on the assumed disk temperature structure. These results indicate that icy collisional growth to planetesimally relevant sizes may happen efficiently throughout a disk's lifetime, and is particularly robust at early times when the disk's dust-to-gas ratio is comparable to that of the interstellar medium.

2022ApJ...937...23Z

Magnetohydrodynamic Waves in an Asymmetric Magnetic Slab with Different External Flows

Building on recent studies of the Kelvin-Helmholtz instability (KHI) in the solar atmosphere, we investigate a simple analytical model that can further our understanding of how the presence of bulk flows influences the propagation of magnetohydrodynamic (MHD) waves. Our model builds on a series of recent works on stationary MHD waveguides and looks at a magnetic slab with a density asymmetry, as well as asymmetric background steady flows present in its environment. We obtained approximate solutions to the dispersion relation for the important and applicable limiting cases of a thin or a wide slab, as well as low- and high-β plasmas. We also explored the relation between the angular frequency of trapped MHD waves, the limit for the onset of the KHI, and small parameters describing the flow and density asymmetries. Our analytical investigation is complemented by a numerical analysis for various bulk flow speeds and slab widths. Both these avenues of study reveal that the flow field asymmetry has an important effect on both the cutoff frequencies and the stability of trapped MHD waves in the slab configuration.

2023RNAAS...7...10M

The Abundances of Carbon, Sulfur, Scandium, Titanium, Manganese, Iron, Gallium and Strontium in the Atmosphere of HD144844

Abundances of manganese and gallium are derived in LTE for the B9 Mn P Ga star HD 144844 using the Mn II lines at 4206.37 and 4259.19 Å and the Ga II line at 6334.07 Å including hyperfine spliting and nuclear shifts. Both elements are found to be overabundant, about 7-10 times the manganese abundance, depending on the line of Mn II used, and about 1800 times the solar gallium abundance. The synthesis of three Fe II lines at 4258.15, 4273.33 and 4296.57 Å yields an abundance of iron marginally above the solar iron abundance. The synthesis of other lines in the range 4200 up to 4300 Å yields information on the abundances of carbon and sulfur (0.05 times the solar abundances), of scandium (5 solar), titanium (1.5 solar), strontium (4.5 solar) and samarium (consistent with a 1.0 solar upper limit).

2023ApJ...943...95S

Asteroseismology: Looking for Axions in the Red Supergiant Star Alpha Ori

In this work, for the first time, we use seismic data as well as surface abundances to model the supergiant α-Ori, with the goal of setting an upper bound on the axion-photon coupling constant g <SUB> a γ </SUB>. We find that, in general, stellar models with g <SUB> a γ </SUB> ∈ [0.002; 2.0] × 10<SUP>-10 </SUP>GeV<SUP>-1</SUP> agree with the observational data, but beyond that upper limit, we do not find stellar models that are compatible with the observational constraints and the current literature. From g <SUB> a γ </SUB> = 3.5 × 10<SUP>-10 </SUP>GeV<SUP>-1</SUP> on, the algorithm did not find any fitting models. Even so, all the axionic models considered present distinct internal profiles from the reference case, without axions. Moreover, as the axion energy losses become more significant, the behavior of the stellar models becomes more diversified, even with very similar input parameters. Nonetheless, the consecutive increments of g <SUB> a γ </SUB> still show systematic tendencies, resulting from the axion energy losses. Moreover, we establish three important conclusions: (1) the increased luminosity and higher neutrino production are measurable effects, possibly associated with axion energy losses; (2) stellar models with axion energy loss show a quite distinct internal structure; and (3) the importance of future asteroseismic missions in observing low-degree nonradial modes in massive stars is emphasized-as internal gravity waves probe the near-core regions, where axion effects are most intense. Thus, more seismic data will allow us to constrain g <SUB> a γ </SUB> better and to prove or dismiss the existence of axion energy loss inside massive stars.

2022ApJ...938...74S

A New Approach to Kinetic Energy Flux at the Different Frequencies above the IRIS Bright Points

Various bright structures abound in the chromosphere playing an essential role in the dynamics and evolution therein. Tentatively identifying the wave characteristics in the outer solar atmosphere helps to understand this layer better. One of the most significant aspects of these characteristics is the wave phase speed (PS), which is a dominant contribution to solar coronal heating and energy distribution in the Sun's atmosphere layers. To obtain energy flux (EF), it is necessary to calculate the filling factor (FF) and the PS. In this study, the FF was determined by tracking the size and intensity of the IRIS bright points (BPs). To estimate an accurate PS and EF, it is necessary to know the chromosphere and transition region (TR) thickness and the phase difference between the two desired levels. Chromosphere and TR thickness cannot be measured directly on the disk; this study is performed using spectral data and calibrated based on Doppler velocities. As a result, the PSs in active regions (ARs) and coronal holes (CHs), as well as the IRIS BPs, have been calculated using the cross-power wavelet transform of Doppler velocities. Consequently, about the CH, the PS mean values are from 40 to 180 km s<SUP>-1</SUP> at the network and from 30 to 140 km s<SUP>-1</SUP> at the internetwork; and about the AR, they are from 80 to 540 km s<SUP>-1</SUP> at the network and 70 to 220 km s<SUP>-1</SUP> at the internetwork. Finally, the EF for the IRIS BPs has been calculated in three different frequencies. The results indicate that the network BPs have an influential role in heating the higher layers, while in the internetwork BPs most of the energy returns to the lower layers. <SUP>*</SUP> Released on 2021 March 1

2021AJ....162..211H

Asteroseismology of iota Draconis and Discovery of an Additional Long-period Companion

Giant stars as known exoplanet hosts are relatively rare due to the potential challenges in acquiring precision radial velocities and the small predicted transit depths. However, these giant host stars are also some of the brightest in the sky and so enable high signal-to-noise ratio follow-up measurements. Here, we report on new observations of the bright (V ~ 3.3) giant star ι Draconis (ι Dra), known to host a planet in a highly eccentric ~511 day period orbit. TESS observations of the star over 137 days reveal asteroseismic signatures, allowing us to constrain the stellar radius, mass, and age to ~2%, ~6%, and ~28%, respectively. We present the results of continued radial-velocity monitoring of the star using the Automated Planet Finder over several orbits of the planet. We provide more precise planet parameters of the known planet and, through the combination of our radial-velocity measurements with Hipparcos and Gaia astrometry, we discover an additional long-period companion with an orbital period of $\sim {68}_{-36}^{+60}$ yr. Mass predictions from our analysis place this substellar companion on the border of the planet and brown dwarf regimes. The bright nature of the star combined with the revised orbital architecture of the system provides an opportunity to study planetary orbital dynamics that evolve as the star moves into the giant phase of its evolution.

2023ApJ...942...45L

Are the Heliosphere, Very Local Interstellar Medium, and Local Cavity in Pressure Balance with Galactic Gravity?

The Voyager spacecraft are providing the first in situ measurements of physical properties in the outer heliosphere beyond the heliopause. These data, together with data from the IBEX and Hubble Space Telescope and physical models consistent with these data, now provide critical measurements of pressures in the heliosphere and surrounding interstellar medium. Using these data, we assemble the first comprehensive survey of total pressures inside and outside of the heliopause, in the interstellar gas surrounding the heliosphere, and in the surrounding Local Cavity to determine whether the total pressures in each region are in balance with each other and with the gravitational pressure exerted by the galaxy. We intercompare total pressures in each region that include thermal, nonthermal, plasma, ram, and magnetic pressure components. An important result is the role of dynamic (ram) pressure. Total pressure balance at the heliopause can only be maintained with a substantial contribution of dynamic pressure from the inside. Also, total pressure balance between the outer heliosphere and pristine very local interstellar medium (VLISM) and between the pristine VLISM and the Local Cavity requires large dynamic pressure contributions. *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 NAS AR-09525.01A. These observations are associated with programs #12475, 12596.

2024ApJS..272...41C

Every Data Point Counts: Stellar Flares as a Case Study of Atmosphere-aided Studies of Transients in the LSST Era

Due to their short timescale, stellar flares are a challenging target for the most modern synoptic sky surveys. The upcoming Vera C. Rubin Legacy Survey of Space and Time (LSST), a project designed to collect more data than any precursor survey, is unlikely to detect flares with more than one data point in its main survey. We developed a methodology to enable LSST studies of stellar flares, with a focus on flare temperature and temperature evolution, which remain poorly constrained compared to flare morphology. By leveraging the sensitivity expected from the Rubin system, differential chromatic refraction (DCR) can be used to constrain flare temperature from a single-epoch detection, which will enable statistical studies of flare temperatures and constrain models of the physical processes behind flare emission using the unprecedentedly high volume of data produced by Rubin over the 10 yr LSST. We model the refraction effect as a function of the atmospheric column density, photometric filter, and temperature of the flare, and show that flare temperatures at or above ∼4000 K can be constrained by a single g-band observation at air mass X ≳ 1.2, given the minimum specified requirement on the single-visit relative astrometric accuracy of LSST, and that a surprisingly large number of LSST observations are in fact likely be conducted at X ≳ 1.2, in spite of image quality requirements pushing the survey to preferentially low X. Having failed to measure flare DCR in LSST precursor surveys, we make recommendations on survey design and data products that enable these studies in LSST and other future surveys.

2022PSJ.....3..129B

Mid-ultraviolet Hubble Observations of Europa and the Global Surface Distribution of SO<SUB>2</SUB>

We present spatially resolved reflectance spectra of Europa's surface in the wavelength range of 210-315 nm obtained by the Hubble Space Telescope Imaging Spectrograph in 2018 and 2019. These data provide the first high-quality, near-global spectral observations of Europa from 210 to 240 nm. They show that the reflectance of Europa's leading, trailing, anti-Jovian, and sub-Jovian hemispheres is ~5% near 210 nm, with varying spectral slopes across the mid-UV. This low albedo, even on the more "pristine" leading hemisphere, indicates a lack of the signature far-UV spectral edge characteristic of water ice. We detected and mapped a strong absorption feature at 280 nm that is consistent with an S-O bond that has previously been attributed to SO<SUB>2</SUB> on the surface, hypothesized to be formed through radiolytic processing of Iogenic sulfur ions that have been preferentially emplaced on Europa's trailing hemisphere by Jupiter's magnetic field. Our models show that small inclusions of SO<SUB>2</SUB> (0.1%) within the water ice are sufficient to produce the 280 nm feature without producing a feature at 4.07 μm, which has not been observed in ground-based spectral observations of Europa. This data set is the first to produce a spatially resolved, near-global map of the assumed SO<SUB>2</SUB> feature, which is primarily concentrated near the apex of the trailing hemisphere and correlated with large-scale darker regions in both the visible and the ultraviolet. This distribution is consistent with "cold" exogenic sulfur ion bombardment on Europa.

2024AJ....168...53Y

Investigating Asymmetry Development from SiO to H<SUB>2</SUB>O Maser Regions in VX Sagittarii

Simultaneous very-long-baseline interferometry monitoring observations of H<SUB>2</SUB>O and SiO masers toward VX Sagittarii were conducted from 2014 February to 2019 January. Thirty epochs of observations revealed that the H<SUB>2</SUB>O and SiO masers had asymmetric and ring-like structures, respectively. However, from 2017 September to 2018 March, the SiO maser transformed from a ring-like structure to a northeast–southwest (NE–SW) extension, and the 43.1 and 86.2 GHz SiO maser components had velocities of 39.48 and 10.65 km s<SUP>‑1</SUP> in the NE–SW direction, suggesting a possible localized strong shock wave. The H<SUB>2</SUB>O maser had a double-sided structure oriented in the NE–SW direction with near-stellar velocity components, which aligned with the extended direction of the SiO maser. The nonregular optical brightness and maser intensity variations were speculated to be related to the morphological evolution of the SiO maser. During the stable states attained by regular pulsations, the SiO maser region was presumed to experience radial acceleration, which reverted the SiO maser to a ring-like structure. However, the H<SUB>2</SUB>O maser region, where the acceleration almost terminates, retained its asymmetric morphology due to the prior influence of external forces. The results suggest that substantial energy transfer can alter the dynamics of the SiO maser and surrounding atmosphere, leading to an asymmetric distribution in the H<SUB>2</SUB>O maser region.

2020ApJ...901....6T

Rotational Disruption of Dust and Ice by Radiative Torques in Protoplanetary Disks and the Implications for Observations

Dust and ice mantles on dust grains play an important role in various processes in protoplanetary disks (PPDs) around a young star, including planetesimal formation, surface chemistry, and being the reservoir of water in habitable zones. In this paper, we perform two-dimensional modeling of rotational disruption of dust grains and ice mantles due to centrifugal force within suprathermally rotating grains spun-up by radiative torques for disks around T-Tauri and Herbig Ae/Be stars. We first study rotational disruption of large composite grains and find that large aggregates could be disrupted into individual nanoparticles via the RAdiative Torque Disruption (RATD) mechanism. We then study rotational desorption of ice mantles and ro-thermal desorption of molecules from the ice mantle. We find that ice mantles in the disk's warm surface layer and above can be disrupted into small icy fragments, followed by rapid evaporation of molecules. We suggest that the rotational disruption mechanism can replenish the ubiquitous presence of polycyclic aromatic hydrocarbons/nanoparticles in the hot surface layers of PPDs as observed in mid-IR emission, which are presumably destroyed by extreme ultraviolet (UV) stellar photons. We find that the water snowline is more extended in the presence of rotational desorption, which would decrease the number of comets but increase the number of asteroids formed in the solar nebula. Finally, we suggest that RATD breaking up carbonaceous grains more efficiently than it does silicates might resolve the carbon deficit problem measured on the Earth and rocky bodies.

2023ApJ...947...47K

Detection of Dipole Modulation in CMB Temperature Anisotropy Maps from WMAP and Planck using Artificial Intelligence

Breakdown of rotational invariance of the primordial power spectrum manifests in the statistical anisotropy of the observed Cosmic Microwave Background (CMB) radiation. Hemispherical power asymmetry in the CMB may be caused due to a dipolar modulation, indicating the presence of a preferred direction. Appropriately rescaled local variance maps of the CMB temperature anisotropy data effectively encapsulate this dipolar pattern. As a first-of-its-kind method, we train Artificial Neural Networks (ANNs) with such local variances as input features to distinguish statistically isotropic CMB maps from dipole-modulated ones. Our trained ANNs are able to predict components of the amplitude times the unit vector of the preferred direction for mixed sets of modulated and unmodulated maps, with goodness-of-fit (R <SUP>2</SUP>) scores &gt;0.97 for full sky and &gt;0.96 for partial sky coverage. On all observed foreground-cleaned CMB maps, the ANNs detect the dipolar modulation signal with overall consistent values of amplitudes and directions. This detection is significant at 97.21%-99.38% C.L. for all full sky maps, and at 98.34%-100% C.L. for all partial sky maps. Robustness of the signal holds across full and partial skies, various foreground cleaning methods, inpainting algorithms, instruments, and all the different periods of observation for Planck and WMAP satellites. The significant and robust detection of the signal, in addition to the consistency of values of amplitude and directions, as found independent of any preexisting methods, further mitigates the criticisms of look-elsewhere effects and a posteriori inferences for the preferred dipole direction in the CMB.

2020ApJ...899..140V

A Gaia-based Catalog of Candidate Stripped Nuclei and Luminous Globular Clusters in the Halo of Centaurus A

Tidally stripped galaxy nuclei and luminous globular clusters (GCs) are important tracers of the halos and assembly histories of nearby galaxies, but are difficult to reliably identify with typical ground-based imaging data. In this paper we present a new method to find these massive star clusters using Gaia DR2, focusing on the massive elliptical galaxy Centaurus A (Cen A). We show that stripped nuclei and GCs are partially resolved by Gaia at the distance of Cen A, showing characteristic astrometric and photometric signatures. We use this selection method to produce a list of 632 new candidate luminous clusters in the halo of Cen A out to a projected radius of 150 kpc. Adding in broadband photometry and visual examination improves the accuracy of our classification. In a spectroscopic pilot program we have confirmed five new luminous clusters, which includes the 7th and 10th most luminous GC in Cen A. Three of the newly discovered GCs are further away from Cen A than all previously known GCs. Several of these are compelling candidates for stripped nuclei. We show that our novel Gaia selection method retains at least partial utility out to distances of ∼25 Mpc and hence is a powerful tool for finding and studying star clusters in the sparse outskirts of galaxies in the local universe.

2023ApJ...953..185H

Dark Matter Halo Properties of the Galactic Dwarf Satellites: Implication for Chemo-dynamical Evolution of the Satellites and a Challenge to Lambda Cold Dark Matter

Elucidating dark matter density profiles in Galactic dwarf satellites is essential to understanding not only the quintessence of dark matter, but also the evolution of the satellites themselves. In this work, we present the current constraints on dark matter densities in Galactic ultrafaint dwarf (UFD) and diffuse galaxies. Applying our constructed nonspherical mass models to the currently available kinematic data of the 25 UFDs and two diffuse satellites, we find that whereas most of the galaxies have huge uncertainties on the inferred dark matter density profiles, Eridanus II, Segue I, and Willman 1 favor cuspy central profiles even when considering effects of a prior bias. We compare our results with the simulated subhalos on the plane between the dark matter density at 150 pc and the pericenter distance. We find that the most observed satellites and the simulated subhalos are similarly distributed on this plane, except for Antlia 2, Crater 2, and Tucana 3, which are less than one-tenth of the density. Despite considerable tidal effects, the subhalos detected by commonly used subhalo finders have difficulty explaining such a huge deviation. We also estimate the dynamical mass-to-light ratios of the satellites and confirm the ratio is linked to stellar mass and metallicity. Tucana 3 deviates largely from these relations, while it follows the mass-metallicity relation. This indicates that Tucana 3 has a cored dark matter halo, despite a significant uncertainty in its ratios.

2023ApJ...950..159Z

Characterizing the Conditional Galaxy Property Distribution Using Gaussian Mixture Models

Line-intensity mapping (LIM) is a promising technique to constrain the global distribution of galaxy properties. To combine LIM experiments probing different tracers with traditional galaxy surveys and fully exploit the scientific potential of these observations, it is necessary to have a physically motivated modeling framework. As part of developing such a framework, in this work, we introduce and model the conditional galaxy property distribution (CGPD), i.e., the distribution of galaxy properties conditioned on the host halo mass and redshift. We consider five galaxy properties, including the galaxy stellar mass, molecular gas mass, galaxy radius, gas-phase metallicity, and star formation rate (SFR), which are important for predicting the emission lines of interest. The CGPD represents the full distribution of galaxies in the five-dimensional property space; many important galaxy distribution functions and scaling relations, such as the stellar mass function and SFR main sequence, can be derived from integrating and projecting it. We utilize two different kinds of cosmological galaxy simulations, a semi-analytic model and the IllustrisTNG hydrodynamic simulation, to characterize the CGPD and explore how well it can be represented using a Gaussian mixture model (GMM). We find that with just a few (approximately three) Gaussian components, a GMM can describe the CGPD of the simulated galaxies to high accuracy for both simulations. The CGPD can be mapped to LIM or other observables by constructing the appropriate relationship between galaxy properties and the relevant observable tracers, which will be discussed in future works.

2023PSJ.....4..227L

How Does the Thermal Environment Affect the Exosphere/Surface Interface at Mercury?

The fate of Mercury's exospheric volatiles and, in a lesser way, of the refractory particles absorbed in the first few centimeters of the surface both depend highly on the temperature profile with depth and its diurnal variation. In this paper, we review several mechanisms by which the surface temperature might control the surface/exosphere interface. The day/night cycle of the surface temperature and its orbital variation, the temperature in the permanent shadow regions, and the subsurface temperature profiles are key thermal properties that control the fate of the exospheric volatiles through the volatile ejection mechanisms, the thermal accommodation, and the subsurface diffusion. Such properties depend on the solar illumination from large to small scales but also on the regolith structure. The regolith is also space-weathered by the thermal forcing and by the thermal-mechanical processing. Its composition is changed by the thermal conditions. We conclude by discussing key characteristics that need to be investigated theoretically and/or in the laboratory: the dependency of the surface spectra with respect to temperature, the typical diffusion timescale of the volatile species, and the thermal dependency of their ejection mechanisms.

2020ApJ...889..106Y

Triggering Mechanism and Material Transfer of a Failed Solar Filament Eruption

Solar filament eruptions are often associated with solar flares and coronal mass ejections, which have the greatest impact on space weather. However, the fine structures and the trigger mechanisms of solar filaments are still unclear. To address these issues, we studied a failed solar active-region filament eruption associated with a C-class flare by using high-resolution Hα images from the New Vacuum Solar Telescope, supplemented by EUV observations from the Solar Dynamics Observatory. Before the filament eruption, a small bipolar magnetic field emerged below the filament. Then magnetic reconnection between the filament and the emerging bipolar magnetic field triggered the filament eruption. During the filament eruption, the untwisting motion of the filament can be clearly traced by the eruptive threads. Moreover, the footpoints of the eruptive threads are determined by tracing the descending filament material. Note that the twisted structure of the filament and the right part of the eruptive filament threads cannot be seen before the filament eruption. These eruptive threads in the right part of the filament are found to be rooting in the weak negative polarities near the main negative sunspot. Moreover, a new filament formed in the filament channel due to material injection from the eruptive filament. The above observations and the potential field extrapolations are inclined to support the idea that the filament materials were transferred into the overlying magnetic loops and the nearby filament channel by magnetic reconnection. These observations improve our understanding of the complexity of filament eruptions.

2021PSJ.....2...44B

Low Radio Frequency Observations from the Moon Enabled by NASA Landed Payload Missions

A new era of exploration of the low radio frequency universe from the Moon will soon be underway with landed payload missions facilitated by NASA's Commercial Lunar Payload Services (CLPS) program. CLPS landers are scheduled to deliver two radio science experiments, Radio wave Observations at the Lunar Surface of the photoElectron Sheath (ROLSES) to the nearside and Lunar Surface Electromagnetics Experiment (LuSEE) to the farside, beginning in 2021. These instruments will be pathfinders for a 10 km diameter interferometric array, Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE), composed of 128 pairs of dipole antennas proposed to be delivered to the lunar surface later in the decade. ROLSES and LuSEE, operating at frequencies from ≈100 kHz to a few tens of megahertz, will investigate the plasma environment above the lunar surface and measure the fidelity of radio spectra on the surface. Both use electrically short, spiral-tube deployable antennas and radio spectrometers based upon previous flight models. ROLSES will measure the photoelectron sheath density to better understand the charging of the lunar surface via photoionization and impacts from the solar wind, charged dust, and current anthropogenic radio frequency interference. LuSEE will measure the local magnetic field and exo-ionospheric density, interplanetary radio bursts, Jovian and terrestrial natural radio emission, and the galactic synchrotron spectrum. FARSIDE, and its precursor risk-reduction six antenna-node array PRIME, would be the first radio interferometers on the Moon. FARSIDE would break new ground by imaging radio emission from coronal mass ejections (CME) beyond 2R<SUB>⊙</SUB>, monitor auroral radiation from the B-fields of Uranus and Neptune (not observed since Voyager), and detect radio emission from stellar CMEs and the magnetic fields of nearby potentially habitable exoplanets.

2023ApJ...945L...7K

JWST/MIRI Spectroscopy of the Disk of the Young Eruptive Star EX Lup in Quiescence

EX Lup is a low-mass pre-main-sequence star that occasionally shows accretion-related outbursts. Here, we present JWST/MIRI medium-resolution spectroscopy obtained for EX Lup 14 yr after its powerful outburst. EX Lup is now in quiescence and displays a Class II spectrum. We detect a forest of emission lines from molecules previously identified in infrared spectra of classical T Tauri disks: H<SUB>2</SUB>O, OH, H<SUB>2</SUB>, HCN, C<SUB>2</SUB>H<SUB>2</SUB>, and CO<SUB>2</SUB>. The detection of organic molecules demonstrates that they are back after disappearing during the large outburst. Spectral lines from water and OH are for the first time deblended and will provide a much-improved characterization of their distribution and density in the inner disk. The spectrum also shows broad emission bands from warm, submicron-size amorphous silicate grains at 10 and 18 μm. During the outburst, in 2008, crystalline forsterite grains were annealed in the inner disk within 1 au, but their spectral signatures in the 10 μm silicate band later disappeared. With JWST we rediscovered these crystals via their 19.0, 20.0, and 23.5 μm emission, the strength of which implies that the particles are at ~3 au from the star. This suggests that crystalline grains formed in 2008 were transported outwards and now approach the water snowline, where they may be incorporated into planetesimals. Containing several key tracers of planetesimal and planet formation, EX Lup is an ideal laboratory to study the effects of variable luminosity on the planet-forming material and may provide an explanation for the observed high crystalline fraction in solar system comets.

2021ApJ...909...67C

FANTASY: User-friendly Symplectic Geodesic Integrator for Arbitrary Metrics with Automatic Differentiation

We present FANTASY (Finally A Numerical Trajectory Algorithm both Straightforward and sYmplectic), a user-friendly, open-source symplectic geodesic integrator written in Python. FANTASY is designed to work "out of the box" and does not require anything from the user aside from the metric and the initial conditions for the geodesics. FANTASY efficiently computes derivatives up to machine precision using automatic differentiation, allowing the integration of geodesics in arbitrary space(times) without the need for the user to manually input Christoffel symbols or any other metric derivatives. Further, FANTASY utilizes a Hamiltonian integration scheme that doubles the phase space, where two copies of the particle phase space are evolved together. This technique allows for an integration scheme that is both explicit and symplectic, even when the Hamiltonian is not separable. FANTASY comes prebuilt with second- and fourth-order schemes, and is easily extendable to higher-order schemes. FANTASY also includes an automatic Jacobian calculator that allows for coordinate transformations to be done automatically.

2023ApJ...950..182K

Synthetic Population of Binary Cepheids. II. The Effect of Companion Light on the Extragalactic Distance Scale

Because of their period-luminosity relation (PLR), classical Cepheids play a key role in the calibration of the extragalactic distance scale and the determination of the Hubble-Lemaître constant H <SUB>0</SUB>. Recent findings show that the majority of classical Cepheids should be in binary or multiple systems, which might undermine their accuracy, as the extra-and unaccounted for-light from the companions of Cepheids causes a shift in the PLR. We quantify this shift using synthetic populations of binary Cepheids that we developed for this purpose, as described in Paper I of this series. We find that while all PLRs are shifted toward brighter values due to the excess light from the companions, the bias in the relative distance modulus between two galaxies hosting binary Cepheids can be either positive or negative, depending on the percentage of binary Cepheids in them. If the binarity percentage in the two galaxies is similar, the effect of binarity is canceled. Otherwise, it introduces a shift in the distance modulus of the order of millimagnitudes in the near-infrared passbands and Wesenheit indices, and tens of millimagnitudes in the visual domain; its exact value depends on the variant of the synthetic population (a unique combination of metallicity, star formation history, shape and location of the instability strip, and initial parameter distributions). Such shifts in the distance moduli to Type Ia supernova host galaxies introduce an additional statistical error on H <SUB>0</SUB>, which however does not prevent measuring H <SUB>0</SUB> with a precision of 1%.

2022RNAAS...6..237A

Two Example GRBs Where Fermi LAT "Extended" Data Gives a Better Photon List than "Photon"

When analyzing Fermi LAT data for temporally contained events like gamma-ray bursts (GRBs), the best data type for analyses is "Extended," not "Photon." Although this is already recommended by the online Fermi website, it is easy to overlook and can lead to inferior analyses. Most extended "events" that are temporally and angularly consistent with GRBs are probably photons. While preparing GRB data for other research projects, the authors encountered this counter-intuitive fact several times. The data from two GRBs are presented with a simple analysis as a demonstration.

2024AJ....167...67A

Toward a Spectrophotometric Characterization of the Chilean Night Sky. A First Quantitative Assessment of ALAN across the Coquimbo Region

Light pollution is recognized as a global issue that, like other forms of anthropogenic pollution, has a significant impact on ecosystems and adverse effects on living organisms. Plentiful evidence suggests that it has been increasing at an unprecedented rate at all spatial scales. Chile-which, thanks to its unique environmental conditions, has become one of the most prominent astronomical hubs of the world-seems to be no exception. In this paper we present the results of the first observing campaign aimed at quantifying the effects of artificial lights at night on the brightness and colors of the Chilean sky. Through the analysis of photometrically calibrated all-sky images captured at four representative sites with an increasing degree of anthropization, and the comparison with state-of-the-art numerical models, we show that significant levels of light pollution have already altered the appearance of the natural sky even in remote areas. Our observations reveal that the light pollution level recorded in a small town of the Coquimbo Region is comparable with that of Flagstaff, Arizona, a ten times larger Dark Sky city, and that a mid-size urban area that is a gateway to the Atacama Desert displays photometric indicators of night sky quality that are typical of the most densely populated regions of Europe. Our results suggest that there is still much to be done in Chile to keep light pollution under control and thus preserve the darkness of its night sky-a natural and cultural heritage that it is our responsibility to protect.

2024AJ....167...22D

Optimal Frequency-domain Analysis for Spacecraft Time Series: Introducing the Missing-data Multitaper Power Spectrum Estimator

While the Lomb-Scargle periodogram is foundational to astronomy, it has a significant shortcoming: the variance in the estimated power spectrum does not decrease as more data are acquired. Statisticians have a 60 yr history of developing variance-suppressing power spectrum estimators, but most are not used in astronomy because they are formulated for time series with uniform observing cadence and without seasonal or daily gaps. Here we demonstrate how to apply the missing-data multitaper power spectrum estimator to spacecraft data with uniform time intervals between observations but missing data during thruster fires or momentum dumps. The F-test for harmonic components may be applied to multitaper power spectrum estimates to identify statistically significant oscillations that would not rise above a white noise-based false alarm probability. Multitapering improves the dynamic range of the power spectrum estimate and suppresses spectral window artifacts. We show that the multitaper-F-test combination applied to Kepler observations of KIC 6102338 detects differential rotation without requiring iterative sinusoid fitting and subtraction. Significant signals reside at harmonics of both fundamental rotation frequencies and suggest an antisolar rotation profile. Next we use the missing-data multitaper power spectrum estimator to identify the oscillation modes responsible for the complex "scallop-shell" shape of the K2 light curve of EPIC 203354381. We argue that multitaper power spectrum estimators should be used for all time series with regular observing cadence.

2022ApJ...936..123J

TIC 5724661: A Long-period Binary with a Pulsating sdB Star and δ Scuti Variable

Using TESS 20 s cadence data, we have discovered an unusual combination of pulsating stars in what we infer to be a binary system. The binary consists of a standard δ Scuti star with pulsations over the range 32-41 day<SUP>-1</SUP>; this is in a likely wide orbit with a hot subdwarf-B (sdB) star, which itself has a large-amplitude p-mode pulsation at 524 day<SUP>-1</SUP>. We establish constraints on the period of the putative binary by using radial velocity measurements of the δ Scuti star and show that any sdB companion star must orbit with a period greater than approximately thirty days. Our identification of this sdB binary serves as an important addition to the relatively small number of sdB binaries known to have orbital periods longer than a few days. We model such a binary using MESA and find that this system could be formed through stable, nonconservative mass transfer from either a low-mass or an intermediate-mass progenitor, without undergoing a common-envelope phase.

2022AJ....164..194V

Apsidal Motion and Physical Parameters in the Eclipsing System V490 Sct

We report long-term UBVRIR <SUB> c </SUB> I <SUB> c </SUB> photometry of the highly eccentric 12.04 day detached eclipsing binary V490 Sct (V = 13.1, B9.5+A0, e = 0.40), which we use to determine its relative and absolute parameters. The absolute masses, radii, and temperatures are M <SUB> A </SUB> = 2.33 ± 0.07 M<SUB>⊙</SUB>, R <SUB> A </SUB> = 1.90 ± 0.04 R <SUB>⊙</SUB>, and T <SUB> A </SUB> = 9960 ± 60 K for the primary and M <SUB> B </SUB> = 2.23±0.07 M<SUB>⊙</SUB>, R <SUB> B </SUB> = 1.86 ± 0.04 R <SUB>⊙</SUB>, and T <SUB> B </SUB> = 9700 ± 80 K for the secondary. The system displays a slow periastron advance that is dominated by General Relativity (GR). Our measurement, $\dot{\omega }=0.86$ deg century<SUP>-1</SUP>, is 32% less then the expected rate, $\dot{\omega }\,=\,1.24$ deg century<SUP>-1</SUP>, which has an 83% contribution from GR. A comparison with current stellar evolution models shows a good match to the measured properties at an age of about 130 Myr and Solar abundance. The photometric parallax of the system π = 0.73 ± 0.04 mas, matches the GAIA DR2 value, π = 0.76 ± 0.04 mas.

2023RNAAS...7..168W

A Dataset for Exploring Stellar Activity in Astrometric Measurements from SDO Images of the Sun

We present a data set for investigating the impact of stellar activity on astrometric measurements using NASA's Solar Dynamics Observatory (SDO) images of the Sun. The sensitivity of astrometry for detecting exoplanets is limited by stellar activity (e.g., starspots), which causes the measured "center of flux" of the star to deviate from the true, geometric, center, producing false positive detections. We analyze Helioseismic and Magnetic Imager continuum image data obtained from SDO between 2015 July and 2022 December to examine this "astrometric jitter" phenomenon for the Sun. We employ data processing procedures to clean the images and compute the time series of the sunspot-induced shift between the center of flux and the geometric center. The resulting time series show quasiperiodic variations up to 0.05% of the Sun's radius at its rotation period.

2023AJ....165...66F

Identifying Diffuse Spatial Structures in High-energy Photon Lists

Data from high-energy observations are usually obtained as lists of photon events. A common analysis task for such data is to identify whether diffuse emission exists, and to estimate its surface brightness, even in the presence of point sources that may be superposed. We have developed a novel nonparametric event list segmentation algorithm to divide up the field of view into distinct emission components. We use photon location data directly, without binning them into an image. We first construct a graph from the Voronoi tessellation of the observed photon locations and then grow segments using a new adaptation of seeded region growing that we call Seeded Region Growing on Graph, after which the overall method is named SRGonG. Starting with a set of seed locations, this results in an oversegmented data set, which SRGonG then coalesces using a greedy algorithm where adjacent segments are merged to minimize a model comparison statistic; we use the Bayesian Information Criterion. Using SRGonG we are able to identify point-like and diffuse extended sources in the data with equal facility. We validate SRGonG using simulations, demonstrating that it is capable of discerning irregularly shaped low-surface-brightness emission structures as well as point-like sources with strengths comparable to that seen in typical X-ray data. We demonstrate SRGonG's use on the Chandra data of the Antennae galaxies and show that it segments the complex structures appropriately.

2023ApJ...955L..21N

X-Ray Detection of the Galaxy's Missing Baryons in the Circumgalactic Medium of L* Galaxies

The number of baryons hosted in the disks of galaxies is lower than expected based on the mass of their dark matter halos and the fraction of baryon-to-total matter in the Universe, giving rise to the so-called galaxy missing-baryon problem. The presence of cool circumgalactic matter gravitationally bound to its galaxy's halo up to distances of at least 10 times the size of the galaxy's disk mitigates the problem but is far from being sufficient for its solution. It has instead been suggested that the galaxy's missing baryons may hide in a much hotter gaseous phase of the circumgalactic medium, possibly near the halo virial temperature and coexisting with the cool phase. Here we exploit the best available X-ray spectra of known cool circumgalactic absorbers of L* galaxies to report the first direct high statistical significance (best estimates ranging from 4.2σ to 5.6σ, depending on fitting methodology) detection of associated O VII absorption in the stacked XMM-Newton and Chandra spectra of three quasars. We show that these absorbers trace the hot medium in the X-ray halo of these systems at logT(in K) ≃ 5.8-6.3 (comprising the halo virial temperature T <SUB>vir</SUB> ≃ 10<SUP>6</SUP> K). We estimate masses of the X-ray halo within one virial radius within the interval ${M}_{\mathrm{hot}-\mathrm{CGM}}\simeq {(1\mbox{--}1.7)\times {10}^{11}(Z/0.3{Z}_{\odot })}^{-1}$ M <SUB>⊙</SUB>. For these systems, this corresponds to galaxy missing-baryon fractions in the range ${\xi }_{b}={M}_{\mathrm{hot}-\mathrm{CGM}}/{M}_{\mathrm{missing}}\simeq {(0.7\mbox{--}1.2)(Z/0.3{Z}_{\odot })}^{-1}$ , thus potentially closing the galaxy baryon census in typical L* galaxies. Our measurements contribute significantly to the solution of the long-standing galaxy missing-baryon problem and to the understanding of the continuous cycle of baryons in-and-out of galaxies throughout the life of the Universe.

2021AJ....162...98B

Seeking Echoes of Circumstellar Disks in Kepler Light Curves

Light echoes of flares on active stars offer the opportunity for direct detection of circumstellar dust. We revisit the problem of identifying faint echoes in postflare light curves, focusing on debris disks from ongoing planet formation. Starting with simulations, we develop an algorithm for estimating the radial extent and total mass from disk echo profiles. We apply this algorithm to light curves from over 2100 stars observed by NASA's Kepler mission, selected for multiple short-lived flares in either the long-cadence or short-cadence data sets. While flux uncertainties in light curves from individual stars preclude useful mass limits on circumstellar disks, catalog-averaged light curves yield constraints on disk mass that are comparable to estimates from known debris disks. The average mass in micron- to millimeter-sized dust around the Kepler stars cannot exceed 10% of an Earth mass in exo-Kuiper belts or 10% of a lunar mass in the terrestrial zone. We group stars according to IR excess, based on WISE W1-W3 color, as an indicator for the presence of circumstellar dust. The mass limits are greater for stars with strong IR excess, a hint that echoes are lurking not far beneath the noise in postflare light curves. With increased sensitivity, echo detection will let time-domain astronomy complement spectroscopic and direct-imaging studies in mapping how, when, and where planets form.

2021ApJ...918....2C

Constraining Spatial Densities of Early Ice Formation in Small Dense Molecular Cores from Extinction Maps

Tracing dust in small dense molecular cores is a powerful tool to study the conditions required for ices to form during the prestellar phase. To study these environments, five molecular cores were observed: three with ongoing low-mass star formation (B59, B335, and L483), and two starless collapsing cores (L63 and L694-2). Deep images were taken in the infrared JHK bands with the United Kingdom Infrared Telescope WFCAM (Wide Field Camera) instrument and IRAC channels 1 and 2 on the Spitzer Space Telescope. These five photometric bands were used to calculate extinction along the line of sight toward background stars. After smoothing the data, we produced high spatial resolution extinction maps (~13″-29″). The maps were then projected into the third dimension using the AVIATOR algorithm implementing the inverse Abel transform. The volume densities of the total hydrogen were measured along lines of sight where ices (H<SUB>2</SUB>O, CO, and CH<SUB>3</SUB>OH) have previously been detected. We find that lines of sight with pure CH<SUB>3</SUB>OH or a mixture of CH<SUB>3</SUB>OH with CO have maximum volume densities above 1.0 × 10<SUP>5</SUP> cm<SUP>-3</SUP>. These densities are only reached within a small fraction of each of the cores (~0.3%-2.1%). CH<SUB>3</SUB>OH presence may indicate the onset of complex organic molecule formation within dense cores, and thus we can constrain the region where this onset can begin. The maximum volume densities toward star-forming cores in our sample (~(1.2-1.7) × 10<SUP>6</SUP> cm<SUP>-3</SUP>) are higher than those toward starless cores (~(3.5-9.5) × 10<SUP>5</SUP> cm<SUP>-3</SUP>).

2022ApJ...941...53G

The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies. III. The Link to the M <SUB>•</SUB>-M <SUB>*</SUB> Correlation

We continue to explore the relationship between the total number of globular clusters (GCs), N <SUB>GC</SUB>, and the central black hole mass, M <SUB>•</SUB>, in spiral galaxies. We present here results for the Sab galaxies NGC 3368, NGC 4736 (M94), and NGC 4826 (M64), and the Sm galaxy NGC 4395. The GC candidate selection is based on the (u* - $i^{\prime} $ ) versus ( $i^{\prime} $ - K <SUB> s </SUB>) color-color diagram, and $i^{\prime} $ -band shape parameters. We determine the M <SUB>•</SUB> versus N <SUB>GC</SUB> correlation for these spirals, plus NGC 4258, NGC 253, M104, M81, M31, and the Milky Way. We also redetermine the correlation for the elliptical sample in Harris et al., with updated galaxy types from Sahu et al. Additionally, we derive the total stellar galaxy mass, M <SUB>*</SUB>, from its two-slope correlation with N <SUB>GC</SUB>, and fit M <SUB>•</SUB> versus M <SUB>*</SUB> for both spirals and ellipticals. We obtain log M <SUB>•</SUB> ∝ (1.01 ± 0.13) log N <SUB>GC</SUB> for ellipticals, and log M <SUB>•</SUB> ∝ (1.64 ± 0.24) log N <SUB>GC</SUB> for late-type galaxies (LTGs). The linear M <SUB>•</SUB> versus N <SUB>GC</SUB> correlation in ellipticals could be due to statistical convergence through mergers, unlike the much steeper correlation for LTGs. However, in the M <SUB>•</SUB> versus total stellar mass (M <SUB>*</SUB>) parameter space, with M <SUB>*</SUB> derived from its correlation with N <SUB>GC</SUB>, M <SUB>•</SUB> ∝ (1.48 ± 0.18) log M <SUB>*</SUB> for ellipticals, and M <SUB>•</SUB> ∝ (1.21 ± 0.16) log M <SUB>*</SUB> for LTGs. The observed agreement between ellipticals and LTGs in this parameter space may imply that black holes and galaxies coevolve through calm accretion, active galactic nuclei feedback, and other secular processes.

2023ApJ...958...73G

Morphology of Star-forming Clumps in Ram-pressure Stripped Galaxies as Seen by HST

We characterize the morphological properties of a statistically relevant sample of Hα and UV young star-forming clumps and optical complexes, observed with the Hubble Space Telescope in six galaxies of the GASP sample undergoing ram pressure stripping. The catalogs comprise 2406 (323 in the tails) Hα clumps, 3750 (899) UV clumps, and 424 tail optical complexes. About 15%-20% of the clumps and 50% of the complexes are resolved in size. We find that more than half of the complexes contain no Hα clumps, while most of them contain at least one UV clump. The clump number and size increase with the complex size, while the median complex filling factor is larger for UV clumps (0.27) than that for Hα clumps (0.10) and does not correlate with almost any morphological property. This suggests that the clumps' number and size grow with the complex keeping the filling factor constant. When studying the position of the clumps inside their complexes, Hα clumps, and UV clumps to a lesser extent, show a displacement from the complex center of 0.1-1 kpc, and in ~60% of the cases, they are displaced away from the galactic disk. This is in accordance with the fireball configuration, already observed in the tails of stripped galaxies. Finally, the filling factor and the clump radius increase with the distance from the galactic disk, suggesting that the reciprocal displacement of the different stellar generations increases as a consequence of the velocity gradient caused by ram pressure.

2024AJ....168...28T

Speckle Interferometry at SOAR Telescope in 2023

Results of the speckle-interferometry observations at the 4.1 m Southern Astrophysical Research Telescope obtained during 2023 are presented: 1913 measurements of 1533 resolved pairs or subsystems (median separation 0.″16) and nonresolutions of 552 targets; 42 pairs are resolved here for the first time. This work continues our long-term effort to monitor orbital motion in close binaries and hierarchical systems. A large number (147) of orbits have been determined for the first time or updated using these measurements. Complementarity of this program with the Gaia mission is highlighted.

2022ApJ...933..147B

Spectra of Cosmic-Ray Sodium and Aluminum and Unexpected Aluminum Excess

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$ , e <SUP>±</SUP>, and nuclei (H-Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to ~2 TV. Given their low solar system abundances, a significant fraction of each element is produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. In this paper, we use precise measurements of the sodium and aluminum spectra by AMS-02 together with ACE-CRIS and Voyager 1 data to test their origin. We show that the sodium spectrum agrees well with the predictions made with the GALPROP-HELMOD framework, while the aluminum spectrum shows a significant excess in the rigidity range from 2-7 GV. In this context, we discuss the origin of other low-energy excesses in Li, F, and Fe found earlier. The observed excesses in Li, F, and Al appear to be consistent with the local Wolf-Rayet stars hypothesis, invoked to reproduce anomalous <SUP>22</SUP>Ne/<SUP>20</SUP>Ne, <SUP>12</SUP>C/<SUP>16</SUP>O, and <SUP>58</SUP>Fe/<SUP>56</SUP>Fe ratios in CRs, while excess in Fe is likely connected with a past supernova activity in the solar neighborhood. We also provide updated local interstellar spectra (LIS) of sodium and aluminum in the rigidity range from a few megavolts to ~2 TV. Our calculations employ the self-consistent GALPROP-HELMOD framework, which has proved to be a reliable tool in deriving the LIS of CR $\bar{p}$ , e <SUP>-</SUP>, and nuclei Z ≤ 28.

2021AJ....162...11L

EDEN: Flare Activity of the Nearby Exoplanet-hosting M Dwarf Wolf 359 Based on K2 and EDEN Light Curves

We report the flare activity of Wolf 359, the fifth closest star to the Sun and a candidate exoplanet-hosting M dwarf. The star was a target of the Kepler/K2 mission and was observed by the EDEN project, a global network of 1-2 m class telescopes for detection and characterization of rocky exoplanets in the habitable zones of late-M dwarfs within 50 light year from the solar system. In the combination of the archived K2 data and our EDEN observations, a total of 872 flares have been detected, 861 with the K2 (860 in the short-cadence and 18 in the long-cadence data, with 17 long-cadence events having short-cadence counterparts) and 11 with EDEN. Wolf 359 has relatively strong flare activity even among flaring M dwarfs, in terms of the flare activity indicator (FA) defined as the integrated flare energy relative to the total stellar bolometric energy, where FA = ∑E<SUB>f</SUB>/∫L<SUB>bol</SUB> dt ∼ 8.93 × 10<SUP>-5</SUP> for the long-cadence flares, whereas for K2 short cadence and EDEN flares, the FA values are somewhat larger, FA ≈ 6.67 × 10<SUP>-4</SUP> and FA ≈ 5.25 × 10<SUP>-4</SUP>, respectively. Such a level of activity, in accordance with the rotation period (P<SUB>rot</SUB>), suggests the star to be in the saturation phase. The size of the starspots is estimated to be at least 1.87% ± 0.59% of the projected disk area of Wolf 359. We find no correlation of FA with the stellar rotational phase. Our analysis indicates a flare frequency distribution in a power-law form of ${dN}/{dE}\propto {E}^{-\alpha }$ with α = 2.13 ± 0.14, equivalent to an occurrence rate of flares E<SUB>f</SUB> ≥ 10<SUP>31</SUP> erg about once per day and of superflares with E<SUB>f</SUB> ≥ 10<SUP>33</SUP> erg approximately 10 times per year. These superflares may impact the habitability of system in multiple ways, the details of which are topics for future investigations.

2022AJ....164...66V

Powerful Flare Phenomena in Water Vapor Maser Lines in the Emerging Protostellar System with Protoplanetary Disks IRAS 16293-2422

According to the detailed monitoring of the water maser at a frequency of 22.2 GHz from 2019 to 2021 in IRAS 16293-2422, two powerful phenomena that occurred at radial velocities of about 6 and 8 km s<SUP>-1</SUP> were detected. Each flare phenomenon consisted of several separate flares lasting no more than a month. The existence of the several emitting maser spot configurations with very close radial velocities, located in the line of sight of the observer, were confirmed for the first time. This made possible to demonstrate the plausibility of the water maser activation hypothesis based on an increase in the amplification length of the maser due to several maser condensations. In both cases, powerful short flares were located on the top of less powerful, but more prolonged ones. Their radiation initiated the release of more powerful flares. The broad Doppler spectral lines of less powerful flares indicate that their masers are probably in a saturated state, while more powerful masers are in unsaturated state. New important parameters of water masers have been obtained, including flare amplitudes, maser line widths, H<SUB>2</SUB>O kinetic temperatures during flares, data on the relaxation time of the maser medium, and the fact of existence of a cascade amplification of the water maser in cases of powerful short flares. The possible localization of water masers at features near 6 and 8 km s<SUP>-1</SUP> within the young gas and dust complex IRAS 16293-2422 is also discussed in this work.

2023ApJ...952L..24A

The Luminosity-Area Relation of z &gt; 2 Quasars' Lyα Nebulae

Cool (T ~ 10<SUP>4</SUP> K) gas is commonly observed around z &gt; 2 quasars as traced by extended Lyα emission. These large-scale nebulae are usually studied using circularly averaged surface-brightness profiles, which suppress information on morphological differences. Here, we revisit the Lyα nebulae around 78 z ~ 2-3 quasars to obtain a novel estimate of their area and asymmetry using a common redshift-corrected surface-brightness threshold. We find a luminosity-area relation of the form $\mathrm{log}({L}_{\mathrm{Ly}\alpha }^{\mathrm{Neb}})={a}_{1}\mathrm{log}({\mathrm{Area}}^{\mathrm{Neb}})+{a}_{0}$ . Most nebulae are symmetric and bright, the most lopsided ones being the faintest and less extended. The enormous Lyα nebulae, asymmetric due to the presence of active companions, are the exceptions to this trend. By using simulations able to reproduce z ~ 6 quasars' nebulae, we show that the observed relation should not vary with redshift. Finally, we discuss possible mechanisms that drive the relation and future work needed to constrain them.

2023ApJ...956..122I

On the Encounter between the GASP Galaxy JO36 and the Radio Plume of GIN 049

We report the serendipitous discovery of an unprecedented interaction between the radio lobe of a radio galaxy and a spiral galaxy. The discovery was made thanks to LOFAR observations at 144 MHz of the galaxy cluster A160 (z = 0.04317) provided by the LOFAR Two-metre Sky Survey. The new low-frequency observations revealed that one of the radio plumes of the central galaxy GIN 049 overlaps the spiral galaxy JO36. Previous studies carried out with MUSE revealed that the warm ionized gas in the disk of JO36, traced by the Hα emission, is severely truncated with respect to the stellar disk. We further explore this unique system by including new uGMRT observations at 675 MHz to map the spectral index. The emerging scenario is that JO36 has interacted with the radio plume in the past 200-500 Myr. The encounter resulted in a positive feedback event for JO36 in the form of a star formation rate burst of ~14 M <SUB>⊙</SUB> yr<SUP>-1</SUP>. In turn, the galaxy passage left a trace in the radio-old plasma by reshaping the old relativistic plasma via magnetic draping.

2021AJ....162..177P

Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. XI. Optical Observations from SOAR, Blanco, NTT and OAN-SPM. The Story So Far

Blazars represent about 62% of the sources in the γ-ray Fermi-LAT catalog, and about 80% of the γ-ray sources associated with a lower-energy counterpart, dominating the γ-ray sky. In particular, about 42% of the γ-ray blazars are classified as Blazars Candidates of Uncertain type (BCUs) for which spectroscopic observations are mandatory to confirm their blazar nature. Here we report the spectra of 64 targets observed as part of our follow-up optical spectroscopic campaign. This sample includes 62 sources classified in Fermi-LAT catalog as BCUs, one source classified as a generic active galactic nucleus, and one source classified as a BL Lac in Fermi-LAT and as blazar of uncertain type in the Roma-BZCAT catalog. We confirm the blazar nature of all BCUs. We classify 33 of them as BL Lacs, 11 as Flat Spectrum Radio Quasars, and 18 as blazars with nonnegligible host-galaxy emission. We also classify the generic active galactic nucleus as a BL Lac. Finally, we confirm the classification of the BL Lac. We also reported a lower limit redshift for 43 sources. For 20 sources, we got redshift measurements consistent with the literature values. For the other 21 sources, we obtained their first spectroscopic redshift measurement; while, for two sources, we provide lower limits on the redshift. With the upcoming release of the sixth edition of the Roma-BZCAT Multifrequency Catalog of Blazars, we take the opportunity in the present work to present the collective results of the first phase of our optical spectroscopic follow-up campaign.

2020PASP..132l4501R

Development of the MICADO Flat-field and Wavelength Calibration Unit: From Design to Prototyping

We describe the evolution and the analysis of the design that led to the development of the Flat-field and wavelength Calibration Unit (FCU) for the Multi-AO Imaging CAmera for Deep Observations (MICADO) instrument. MICADO will be one of the first light instruments of the Extremely Large Telescope. The FCU challenge in terms of calibration is related to the large size of the MICADO entrance and final focal plane, ∼200 mm × 200 mm. Such a focal plane scale and its segmentation in 3 × 3 detectors, require significant design modifications with respect to the calibration units of the current and past generation of instruments. The design analysis and ray tracing calculations are complemented with the test and verification of lab prototypes to assess the reliability of the FCU architecture in terms of flat-field illumination uniformity and signal to noise, spectral calibration line coverage and radial velocity stability of the wavelength solution provided to the instrument.

2024ApJ...962L..40C

The First Robust Evidence Showing a Dark Matter Density Spike Around the Supermassive Black Hole in OJ 287

Black hole dynamics suggests that dark matter would redistribute near a supermassive black hole (SMBH) to form a density spike. However, no direct evidence of a dark matter density spike around an SMBH has been identified. In this Letter, we present the first robust evidence showing a dark matter density spike around an SMBH. We revisit the data of the well-known SMBH binary OJ 287 and show that the inclusion of the dynamical friction due to a dark matter density spike around the SMBH can satisfactorily account for the observed orbital decay rate. The derived spike index ${\gamma }_{\mathrm{sp}}={2.351}_{-0.045}^{+0.032}$ gives an excellent agreement with the value γ <SUB>sp</SUB> = 2.333 predicted by the benchmark model assuming an adiabatically growing SMBH. This provides a strong verification of the canonical theory suggested two decades ago modeling the gravitational interaction between collisionless dark matter and SMBHs.

2022AJ....164..230S

The Arizona Radio Observatory 1 mm Spectral Survey of the Hypergiant Star NML Cygni (215-285 GHz)

A sensitive (1σ rms ≤ 3 mK; 2 MHz resolution) 1 mm spectral survey (214.5-285.5 GHz) of the envelope of the oxygen-rich supergiant star NML Cygni (NML Cyg) has been conducted using the 10 m Submillimeter Telescope of the Arizona Radio Observatory. These data represent the first spectral line survey of NML Cyg and are complementary to a previous 1 mm survey of the envelope of a similar hypergiant, VY Canis Majoris (VY CMa). The complete NML Cyg data set is presented here. In the survey, 104 emission lines were observed, arising from 17 different molecules and 4 unidentified features. Many of the observed features have complex line profiles, arising from asymmetric outflows characteristic of hypergiant stars. While most of the lines in the survey arise from SiO, SO, SO<SUB>2</SUB>, and SiS, CO had the strongest emission. Five other C-bearing species are identified in the survey (HCN, CN, HCO<SUP>+</SUP>, CS, and HNC), demonstrating an active carbon chemistry despite the O-rich environment. Moreover, NS was observed, but not NO, although favorable transitions of both molecules lie in the surveyed region. Sulfur chemistry appears to be prominent in NML Cyg and plays an important role in the collimated outflows. The refractory species observed, NaCl and AlO, have narrow emission lines, indicating that these molecules do not reach the terminal expansion velocity. NaCl and AlO likely condense into dust grains at r &lt; 50 R <SUB>*</SUB>. From NaCl, the chlorine isotope ratio was determined to be <SUP>35</SUP>Cl/<SUP>37</SUP>Cl = 3.85 ± 0.30.

2022PSJ.....3...99W

Polar Ice Accumulation from Volcanically Induced Transient Atmospheres on the Moon

Water ice exists at the lunar poles, but its origin, abundance, and distribution are not well understood. One potential source of water to the poles is the volcanic outgassing of volatiles from the lunar interior and subsequent condensation of erupted water vapor as surface ice. We investigate whether volcanic outgassing is a viable source for the accumulation of lunar polar water ice. We construct a model that accounts for volcanic outgassing, atmospheric escape to space, and surface ice accumulation over the period of peak lunar volcanic activity (4-2 Ga) and map the resulting water ice distribution and abundance using current surface temperature data from the Lunar Reconnaissance Orbiter. Our model suggests that ~41% of the total H<SUB>2</SUB>O mass erupted over this period could have condensed as ice in the polar regions, with thicknesses up to several hundreds of meters. The south pole accumulates roughly twice the ice mass of the north, and the southern deposits are thicker. Typical modeled eruptions generate collisional atmospheres with lifetimes of ~2500 yr. However, these atmospheres are episodic and generally do not persist between eruptions. Roughly 15% of an atmosphere's water vapor mass forms a frost on the lunar nightside, while the transient atmosphere persists. Our work suggests that the volcanically active period of the early Moon would have been punctuated by short-lived, collisional atmospheres that enabled the efficient sequestration of large quantities (8.2 × 10<SUP>15</SUP> kg) of water ice at the poles and the temporary diurnal availability of water ice and vapor at all latitudes.

2023AJ....165..212A

To Be or Not to Be: Alicante-8, a Cluster or Not?

Recent surveys have uncovered new young massive clusters that host dozens of red supergiants (RSGs) near the inner Galaxy. However, many of them have still not been fully studied. Using Very Large Telescope/X-shooter near-infrared spectra, we present the first radial velocity analysis for the putative members of the candidate RSG cluster Alicante-8. Our results show a large dispersion of radial velocities among the candidate member stars, indicating that Alicante-8 does not seem to be a real cluster, unlike Alicante-7 and Alicante-10, which are confirmed by the distribution of the radial velocities of their RSG members. Measuring the spectral indices reveals that the assumption that the candidate stars are RSGs was incorrect, leading to the misclassification of Alicante-8 as a candidate RSG cluster. Our results imply that spectral classification based on the widely used CO band at 2.3 μm alone is not a sufficient criterion, because both red giants and RSGs can attain similar CO equivalent widths, and that spectroscopic radial velocities are needed in order to confirm unambiguously the cluster membership.

2023ApJ...959...30S

Probing Orbital Parameters of Gamma-Ray Binaries with TeV Light Curves

Gamma-ray binaries are binary systems in which the energy flux peaks in the gamma-ray energy band. They harbor a compact object (a neutron star or a black hole) orbiting around a massive star, which provides a strong radiation field. It is believed that the gamma-ray emission from such objects can be strongly attenuated through the electron-positron pair production in gamma-gamma interactions. The importance of gamma-gamma absorption depends on the orbital phase and on the geometry of the system. In this work, we propose a method showing how the orbital parameters of gamma-ray binaries could be probed with TeV light curves that have imprinted features of gamma-gamma absorption.