119269007
TYPE-I X-RAY BURSTS REVEAL A FAST CO-EVOLVING BEHAVIOR OF THE CORONA IN AN X-RAY BINARY
The coronae in X-ray binaries (XRBs) still remain poorly understood, although they have been believed for a long time to play a key role in modeling the characteristic outbursts of XRBs. Type-I X-ray bursts, the thermonuclear flashes happening on the surface of a neutron star (NS), can be used as a probe to the innermost region of an NS XRB, where the corona is believed to be located very close to the NS. We report the discovery of a tiny life cycle of the corona that is promptly co-evolved with the type-I bursts superimposed on the outburst of the NS XRB IGR J17473-2721. This finding may serve as the first evidence of directly seeing the rapid disappearance and formation of a corona in an XRB with a cooling/heating timescale of less than a second, which can strongly constrain the accretion models in XRBs at work.
15715110
Suppressed star formation in circumnuclear regions in seyfert galaxies
Feedback from black hole activity is widely believed to play a key role in regulating star formation and black hole growth. A long-standing issue is the relation between star formation and the fueling of the supermassive black holes in active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to tackle this issue. We estimate the surface densities of gas and star formation rates in circumnuclear regions (CNRs). Comparing them with the well-known Kennicutt-Schmidt (K-S) law, we find that the star formation rates (SFRs) in the CNRs of most Seyfert galaxies are suppressed in this sample. Feedback is suggested to explain the suppressed SFRs.
119263279
The 2008 outburst of IGR J17473–2721: evidence for a disk corona?
Context. The 2008 outburst of the atoll source IGR J17473–2721 was observed by INTEGRAL, RXTE and Swift. Tens of type-I X-ray bursts were found in this outburst. Aims. Joint observations by INTEGRAL, RXTE, and Swift provide sufficient data to look into the behavior of IGR J17473–2721 at the rising part of the 2008 outburst. The relation between the duration of the bursts and the accretion rate and the nature of the corona producing the observed power-law component can therefore be studied in detail. Methods. We analyze observational data of IGR J17473–2721, focusing on the spectral evolution during the state transition from quiescent to low hard state (LHS), and on the flux dependence of the type-I X-ray bursts along the outburst. Results. We find that the joint INTEGRAL, RXTE and Swift energy spectrum can be well fitted with a model composed of a blackbody and a cutoff power-law, with a cutoff energy decreasing from ∼150 keV to ∼40 keV as the source leaves the quiescent state toward the low hard state. This fits into a scenario in which the corona is cooled by the soft X-rays along the outburst evolution, as observed in several other atoll sources. Fifty-seven type-I bursts were reported in the 2008 outburst of IGR J17473–2721. By using the flux measured in the 1.5–30 keV band, we find that the linear relationship between the burst duration and the flux still holds for those bursts that occur at the decaying part of the low hard state, but with a different slope than the overall one that was estimated with the bursts happening in the whole extent of, and for the rest of the low hard state. The significance of such a dichotomy in the type-I X-ray bursts is ∼3σ under an F-test. Similar results are hinted at as well with the broader energy-band that was adopted recently. This dichotomy may be understood in a scenario where part of the accreting material forms a corona on the way of falling onto the surface of the neutron star during the decaying part of the low hard state.Based on the accretion rates of the preceding LHS, estimated from type-I X-ray bursts and from persistent emission, at least for IGR J17473-2721, most of the accretion material may fall on the neutron star (NS) surface in the LHS. Considering the burst behavior in the context of the outburst indicates a corona formed on top of the disk rather than on the NS surface.
17406200
EVOLUTION OF GASEOUS DISK VISCOSITY DRIVEN BY SUPERNOVA EXPLOSIONS IN STAR-FORMING GALAXIES AT HIGH REDSHIFT
Motivated by Genzel et al.'s observations of high-redshift star-forming galaxies, containing clumpy and turbulent rings or disks, we build a set of equations describing the dynamical evolution of gaseous disks with inclusion of star formation and its feedback. Transport of angular momentum is due to "turbulent" viscosity induced by supernova explosions in the star formation region. Analytical solutions of the equations are found for the initial cases of a gaseous ring and the integrated form for a gaseous disk, respectively. For a ring with enough low viscosity, it evolves in a slow process of gaseous diffusion and star formation near the initial radius. For a high viscosity, the ring rapidly diffuses in the early phase. The diffusion drives the ring into a region with a low viscosity and starts the second phase undergoing pile-up of gas at a radius following the decreased viscosity torque. The third is a sharply decreasing phase because of star formation consumption of gas and efficient transportation of gas inward forming a stellar disk. We apply the model to two z similar to 2 galaxies BX 482 and BzK 6004, and find that they are undergoing a decline in their star formation activity.
14133011
The Unified Model of Active Galactic Nuclei. I. Non-Hidden Broad-Line Region Seyfert 2 and Narrow-Line Seyfert 1 Galaxies
The unified model of Seyfert galaxies suggests that there are hidden broad-line regions (HBLRs) in Seyfert 2 galaxies (S2s). However, there is increasing evidence for the appearance of a subclass of S2s lacking HBLRs (non-HBLR S2s). An interesting issue arises as to the relations of non-HBLR S2s with other types of Seyfert galaxies and whether or not they can be included in the unified model. We assemble two subsamples consisting of 42 non-HBLR S2s and 44 narrow-line Seyfert 1 galaxies (NLS1s) with redshift z ? 0.05 from published literatures to explore this issue. We compare black hole masses in the galactic centers, accretion rates, and infrared color ratio (f60 ?m/f25 ?m) as a potential indicator of the dusty torus orientation, [O III] ?5007, radio, and far-infrared luminosities. We find that non-HBLR S2s and NLS1s have (1) similar distributions of black hole masses [ ? 107 M?] and Eddington ratios (LBol/LEdd ~ 1); (2) significantly different distributions of f60 ?m/f25 ?m ratios; and (3) similar distributions of bulge magnitudes and luminosities of [O III], radio, and far-infrared emission. The similarities and differences can be understood naturally if they are intrinsically the same, but non-HBLR S2s are viewed at larger angles of the observer's sight than NLS1s. We thus suggest that non-HBLR S2s only have narrower broad-line regions and that they are the counterparts of NLS1s viewed at high inclination angles. The absence of the polarized emission line in non-HBLR S2s is caused by the less massive black holes and high accretion rate similar to NLS1s. The implications of the unification scheme of non-HBLR S2s and NLS1s are discussed.
119247847
THE HARD X-RAY BEHAVIOR OF AQL X-1 DURING TYPE-I BURSTS
We report the discovery of an anti-correlation between the soft and hard X-ray light curves of the X-ray binary Aql X-1 when bursting. This behavior may indicate that the corona is cooled by the soft X-ray shower fed by the type-I X-ray bursts, and that this process happens within a few seconds. Stacking the Aql X-1 light curves of type-I bursts, we find a shortage in the 40-50 keV band, delayed by 4.5 ± 1.4 s with respect to the soft X-rays. The photospheric radius expansion bursts are different in that neither a shortage nor an excess shows up in the hard X-ray light curve.
11916638
Precise mass measurement of 68Se, a waiting-point nuclide along the rp process.
Mass measurements of 68Ge, 68As, and 68Se have been obtained with the Canadian Penning Trap mass spectrometer. The results determine the mass excess of 68Se as -54 232(19) keV, the first measurement with a precision and reliability sufficient to address the light-curve and energy output of x-ray bursts as well as the abundances of the elements synthesized. Under typical conditions used for modeling x-ray bursts, 68Se is found to cause a significant delay in the rp process nucleosynthesis.
52992251
VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. V. A LOW ECCENTRICITY BROWN DWARF FROM THE DRIEST PART OF THE DESERT, MARVELS-6b
We describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 ± 2.0 M Jup to GSC 03546-01452 from the MARVELS radial velocity survey, which we designate as MARVELS-6b. For reasonable priors, our analysis gives a probability of 72% that MARVELS-6b has a mass below the hydrogen-burning limit of 0.072 M ☉, and thus it is a high-confidence BD companion. It has a moderately long orbital period of  days with a low eccentricity of , and a semi-amplitude of m s–1. Moderate resolution spectroscopy of the host star has determined the following parameters: T eff = 5598 ± 63, log g = 4.44 ± 0.17, and [Fe/H] = +0.40 ± 0.09. Based upon these measurements, GSC 03546-01452 has a probable mass and radius of M * = 1.11 ± 0.11 M ☉ and R * = 1.06 ± 0.23 R ☉ with an age consistent with less than ~6 Gyr at a distance of 219 ± 21 pc from the Sun. Although MARVELS-6b is not observed to transit, we cannot definitively rule out a transiting configuration based on our observations. There is a visual companion detected with Lucky Imaging at 7.''7 from the host star, but our analysis shows that it is not bound to this system. The minimum mass of MARVELS-6b exists at the minimum of the mass functions for both stars and planets, making this a rare object even compared to other BDs. It also exists in an underdense region in both period/eccentricity and metallicity/eccentricity space.
119280386
Links Between Z Sources and Atoll Sources
It is known that the Z and atoll sources are two typical types of neutron-star sources in low mass X-ray binaries (LMXBs), which present very different Q-ν relations of lower kHz QPOs. We propose that the Z and atoll sources are two different phases in the evolutionary track of neutron star in LMXBs, instead of two types of distinct sources.
16864996
A New Scenario on X-ray Shallow Decay of Gamma-ray Bursts
In this Letter, we propose that a microphysical process takes a vital role in the shocked region in which the prompt emission of GRBs is emitted. The turbulent energy is included in the internal energy transferred by the kinetic energy of the shock. It dissipates through stochastic acceleration for the electrons to supply the early X-ray emission in the phase of shallow decay. We put the constraints on the time evolution of microphysical parameters. The early X-ray fluxes can be obtained by this scenario and these results are consistent with the Swift observation
124445984
The Chiral Anomalies in W and Z Decays
Some of the important W± and Z decay amplitudes, relating to the chiral anomalies of the quark sector in the Standard Model, are given by means of the interactions determined by the effective Lagrangian (action) of the nonlinear σ model for the pseudogoldstone bosons. The corresponding decay rates are calculated. It is shown that the decay rates are quite large, especially, the rate of the decay W →πγ and probably that of W → Dsγ are predicted being unexpectedly great (ΓW→πγ = 0.35 GeV). This indicates that the chiral anomalies and our approach should receive tests from SPPS and Tevantron experiments.