Sazuna/UAT_keywords huggingface dataset:
Isotopic Signatures of Supernova Nucleosynthesis in Presolar Silicon Carbide Grains of Type AB with Supersolar <SUP>14</SUP>N/<SUP>15</SUP>N Ratios. We report high-resolution C, N, Al, Si, and S isotope data of 38 presolar SiC grains of type AB. Seventeen of these grains are of subtype AB1 (14N/15N &lt; 440 = solar) and 20 of subtype AB2 (14N/15N ≥ 440), previously proposed to be mainly from supernovae (AB1) and J-type carbon stars (AB2), respectively. Our data are compatible with previously obtained isotope data of AB grains, except that 26Al/27Al ratios of AB1 grains span a narrower range. The data are compared with predictions from supernova models that consider H ingestion into the He shell during the pre-supernova phase. In these models a mixture of explosive H and He burning occurs at the bottom of the He shell during passage of the supernova shock, forming the so-called O/nova zone. Mixing matter from the O/nova zone with matter from the overlying He/C zone and the stellar envelope shows that the isotopic compositions and trends of both AB1 and AB2 grains can be matched within the model uncertainties. This demonstrates that supernovae should be considered as potential sources of AB2 grains, in addition to J-type carbon stars and born-again asymptotic giant branch stars, as previously proposed.

Keywords: Meteorites, Circumstellar matter, Supernovae, Nucleosynthesis
Inferring Galactic Parameters from Chemical Abundances: A Multi-star Approach. Constraining parameters such as the initial mass function high-mass slope and the frequency of Type Ia supernovae is of critical importance in the ongoing quest to understand galactic physics and create realistic hydrodynamical simulations. In this paper, we demonstrate a method for precisely determining these using individual chemical abundances from a large set of stars, coupled with some estimate of their ages. Inference is performed via the simple chemical evolution model Chempy in a Bayesian framework, marginalizing over each star’s specific interstellar medium parameters, including an element-specific “model error” parameter to account for inadequacies in our model. Hamiltonian Monte Carlo methods are used to sample the posterior function, which is made possible by replacing Chempy with a trained neural network at negligible error. The approach is tested using data from both Chempy and the IllustrisTNG simulation, showing subpercent agreement between inferred and true parameters using data from up to 1600 individual stellar abundances. For IllustrisTNG, the strongest constraints are obtained from metal ratios, competitive with those from other methods including star counts. Analysis using a different set of nucleosynthetic yields shows that incorrectly assumed yield models can give non-negligible bias in the derived parameters; this is reduced by our model errors, which further show how well the yield tables match the data. We also find a significant bias from analyzing only a small set of stars, as is often done in current analyses. The method can be easily applied to observational data, giving tight bounds on key galactic parameters from chemical abundances alone.

Keywords: Astrostatistics tools, Stellar abundances, Interstellar abundances, Chemical abundances, Astrostatistics, Astrochemistry, Milky Way Galaxy physics, Chemical enrichment, Galactic abundances
Revealing Hidden Substructures in the M <SUB>BH</SUB>-σ Diagram, and Refining the Bend in the L-σ Relation. Using 145 early- and late-type galaxies (ETGs and LTGs) with directly measured supermassive black hole masses, M BH, we build upon our previous discoveries that: (i) LTGs, most of which have been alleged to contain a pseudobulge, follow the relation {M}BH}\propto {M}* ,{sph}2.16+/- 0.32; and (ii) the ETG relation {M}BH}\propto {M}* ,{sph}1.27+/- 0.07 is an artifact of ETGs with/without disks following parallel {M}BH}\propto {M}* ,{sph}1.9+/- 0.2 relations that are offset by an order of magnitude in the M BH direction. Here, we searched for substructure in the diagram of M BH versus central velocity dispersion σ, using our recently published multi-component galaxy decompositions, by investigating divisions based on the presence of a depleted stellar core (major dry merger), a disk (minor wet/dry merger, gas accretion), or a bar (evolved unstable disk). The Sérsic and core-Sérsic galaxies define two distinct relations: {M}BH}\propto {σ }5.75+/- 0.34 and {M}BH}\propto {σ }8.64+/- 1.10, with {{{Δ }}}rms| {BH}}=0.55 and 0.46 dex, respectively. We also report on the consistency with the slopes and bends in the galaxy luminosity (L)-σ relation due to Sérsic and core-Sérsic ETGs, and LTGs that all have Sérsic light profiles. Two distinct relations (superficially) reappear in the M BH-σ diagram upon separating galaxies with/without a disk (primarily for the ETG sample), while we find no significant offset between barred and non-barred galaxies, nor between galaxies with/without active galactic nuclei. We also address selection biases purported to affect the scaling relations for dynamically measured M BH samples. Our new M BH-σ relations, dependent on morphological type, more precisely estimate M BH in other galaxies, and hold implications for galaxy/black hole coevolution theories, simulations, feedback, the pursuit of a black-hole fundamental plane, and calibration of virial f-factors for reverberation mapping.

Keywords: Supermassive black holes, Late-type galaxies, Galaxy structure, Early-type galaxies, Scaling relations, Galaxy kinematics, Galaxy evolution, Astrophysical black holes
Learning about the Intermediate Neutron-capture Process from Lead Abundances. Lead (Pb) is predominantly produced by the slow neutron-capture process (s process) in asymptotic giant branch (AGB) stars. In contrast to significantly enhanced Pb abundances predicted by low-mass, low-metallicity AGB models, observations of Magellanic post-AGB stars show incompatibly low Pb abundances. Observations of carbon-enhanced metal-poor (CEMP) stars whose s-process enrichments are accompanied by heavy elements traditionally associated with the rapid neutron-capture process (r process) have raised the need for a neutron-capture process operating at neutron densities intermediate to the s and r process: the so-called i process. We study i-process nucleosynthesis with single-zone nuclear-network calculations. Our i-process models can explain the heavy-element abundance patterns measured in Magellanic post-AGB stars including their puzzlingly low Pb abundances. Furthermore, the heavy-element enhancements in the post-AGB and CEMP-i stars, particularly their Pb abundance, allow us to characterize the neutron densities and exposures of the i process that produced the observed abundance patterns. We find that the lower-metallicity CEMP-i stars (≤ft[{Fe}/{{H}}\right]≈ -2.5) have heavy-element abundances best matched by models with higher neutron densities and exposures (τ &gt; 2.0 mbarn-1) compared to the higher-metallicity post-AGB stars (≤ft[{Fe}/{{H}}\right]≈ -1.3, τ &lt; 1.3 mbarn-1). This offers new constraints and insights regarding the properties of i-process sites and demonstrates that the responsible process operates on timescales of the order of a few years or less. This paper is dedicated to the celebration of the 100th birthday of Margaret Burbidge, in recognition of her outstanding contribution to nuclear astrophysics.

Keywords: Binary stars, Nucleosynthesis, Stellar abundances, Carbon stars, Post-asymptotic giant branch, Asymptotic giant branch stars, Nuclear astrophysics, Stellar nucleosynthesis, CEMP stars, Chemically peculiar stars
Carbon-deficient Red Giants. Carbon-deficient red giants (CDRGs) are a rare class of peculiar red giants, also called “weak G-band” or “weak CH” stars. Their atmospheric compositions show depleted carbon, a low {}12{{C}}{/}13{{C}} isotopic ratio, and an overabundance of nitrogen, indicating that the material at the surface has undergone CN-cycle hydrogen burning. I present Strömgren uvby photometry of nearly all known CDRGs. Barium stars, having an enhanced carbon abundance, exhibit the “Bond-Neff effect”—a broad depression in their energy distributions at ∼4000 Å, recently confirmed to be due to the CH molecule. This gives Ba II stars unusually low Strömgren c 1 photometric indices. I show that CDRGs, lacking CH absorption, exhibit an “anti-Bond-Neff effect”—higher c 1 indices than normal red giants. Using precise parallaxes from Gaia DR2, I plot CDRGs in the color-magnitude diagram (CMD) and compare them with theoretical evolution tracks. Most CDRGs lie in a fairly tight clump in the CMD, indicating initial masses in the range ∼2-3.5 {M}⊙ , if they have evolved as single stars. It is unclear whether they are stars that have just reached the base of the red-giant branch and the first dredge-up of CN-processed material, or are more highly evolved helium-burning stars in the red-giant clump. About 10% of CDRGs have higher masses of ∼4-4.5 {M}⊙ , and exhibit unusually high rotational velocities. I show that CDRGs lie at systematically larger distances from the Galactic plane than normal giants, possibly indicating a role of binary mass transfer and mergers. CDRGs continue to present a major puzzle for our understanding of stellar evolution.

Keywords: Chemically peculiar giant stars, Binary stars, Evolved stars, Carbon-nitrogen cycle, Stellar abundances, Strömgren photometry, Stellar parallax, Stellar rotation
Spectral Analysis of Fermi-LAT Gamma-Ray Bursts with Known Redshift and their Potential Use as Cosmological Standard Candles. Long duration gamma-ray bursts may serve as standard candles to constrain cosmological parameters by probing the Hubble diagram well beyond the range of redshift currently accessible using SNe Ia. The standardization of gamma-ray bursts (GRBs) is based on phenomenological relations between two or more parameters found from spectral modeling, one of which is strongly dependent on the cosmological model. The Amati relation links the source-frame energy {E}{{i},{{p}}} at which the prompt gamma-ray spectral energy distribution νF  ν  peaks, and the isotropic-equivalent bolometric energy {E}iso} emitted during the prompt phase. We performed spectral analysis of 26 GRBs with known redshift that have been detected by the Fermi-Large Area Telescope (LAT) during its nine years of operations from 2008 July to 2017 September, thus extending the computation of E iso to the 100 MeV range. Multiple components are required to fit the spectra of a number of GRBs. We found that the Amati relation is satisfied by the 25 LGRBs, with best-fit parameters similar to previous studies that used data from different satellite experiments, while the only short GRB with known redshift is an outlier. Using the Amati relation, we extend the Hubble diagram to redshift 4.35 and constrain the Hubble constant and dark-energy density in the ΛCDM model, with Fermi-LAT GRBs alone and together with another sample of 94 GRBs and with the latest Supernovae type-Ia data. Our results are consistent with the currently acceptable ranges of those cosmological parameters within errors.

Keywords: Cosmology, Cosmological parameters, Gamma-ray bursts, Astronomical radiation sources
Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Neutral Chlorine. We present lifetime measurements using beam-foil techniques for radiative transitions from the 3p 4(1 S)4s 2 S 1/2, 3p 4(3 P)5 {s}2{P}1/{2,3/2}, and 3p 4(3 P)3d 2 F 5/2 levels in Cl I and the corresponding results of the oscillator strengths for transitions at 1004.68, 1079.88, 1090.73, and 1094.77 Å, respectively. We compare our experimental results with available theoretical calculations and astronomical observations in an effort to resolve discrepancies among them.

Keywords: Atomic physics, Laboratory astrophysics, Interstellar abundances, Ultraviolet astronomy, Interstellar absorption, Transition probabilities
Two New “Turn-off” Changing-look Active Galactic Nuclei and Implication on “Partially Obscured” AGNs. We report a spectroscopic identification of two new changing-look active galactic nuclei (CL-AGNs): SDSS J104705.16+544405.8 and SDSS J120447.91+170256.8, both with a “turn-off” type transition from type-1 to type-1.8/1.9. The identification is arrived at through a follow-up spectroscopic observation of the five CL-AGNs candidates that are extracted from the sample recently released in Macleod et al. The candidates are extracted by the authors from the Sloan Digit Sky Survey Data Release 7, and are spectroscopically confirmed quasars with large amplitude variability. By compiling a sample of 26 previously identified CL-AGNs, we confirm the claim by Macleod et al. that CL-AGNs tend to be biased against a low Eddington ratio, and identify an overlap between the CL-AGNs at their dim state and the so-called intermediate-type AGNs. The overlap implies that there two populations of the intermediate-type AGNs with different origins. One is due to the torus orientation effect, and the other to the intrinsic change of the accretion rate of the central supermassive black holes.

Keywords: Active galactic nuclei, Astrophysical masers, Quasars
On the Prospect of Using the Maximum Circular Velocity of Halos to Encapsulate Assembly Bias in the Galaxy-Halo Connection. We investigate a conceptual modification of the halo occupation distribution approach, using the halos’ present-day maximal circular velocity, V max, as an alternative to halo mass. In particular, using a semianalytic galaxy formation model applied to the Millennium WMAP7 simulation, we explore the extent that switching to V max as the primary halo property incorporates the effects of assembly bias into the formalism. We consider fixed number density galaxy samples ranked by stellar mass and examine the variations in the halo occupation functions with either halo concentration or formation time. We find that using V max results in a significant reduction in the occupancy variation of the central galaxies, particularly for concentration. The satellites’ occupancy variation on the other hand increases in all cases. We find effectively no change in the halo clustering dependence on concentration, for fixed bins of V max compared to fixed halo mass. Most crucially, we calculate the impact of assembly bias on galaxy clustering by comparing the amplitude of clustering to that of a shuffled galaxy sample, finding that the level of galaxy assembly bias remains largely unchanged. Our results suggest that while using V max as a proxy for halo mass diminishes some of the occupancy variations exhibited in the galaxy-halo relation, it is not able to encapsulate the effects of assembly bias potentially present in galaxy clustering. The use of other more complex halo properties, such as V peak, the peak value of V max over the assembly history, provides some improvement and warrants further investigation.

Keywords: Cosmology, Galaxy dark matter halos, Cosmological models, Galaxy formation, Large-scale structure of the universe, Observational cosmology, Cold dark matter, Astrostatistics, Clustering, Galaxy evolution, N-body simulations, Galaxies
Classification of New X-Ray Counterparts for Fermi Unassociated Gamma-Ray Sources Using the Swift X-Ray Telescope. Approximately one-third of the gamma-ray sources in the third Fermi-LAT catalog are unidentified or unassociated with objects at other wavelengths. Observations with the X-Ray Telescope on the Neil Gehrels Swift Observatory (Swift-XRT) have yielded possible counterparts in ∼30% of these source regions. The objective of this work is to identify the nature of these possible counterparts, utilizing their gamma-ray properties coupled with the Swift derived X-ray properties. The majority of the known sources in the Fermi catalogs are blazars, which constitute the bulk of the extragalactic gamma-ray source population. The galactic population on the other hand is dominated by pulsars. Overall, these two categories constitute the majority of all gamma-ray objects. Blazars and pulsars occupy different parameter space when X-ray fluxes are compared with various gamma-ray properties. In this work, we utilize the X-ray observations performed with the Swift-XRT for the unknown Fermi sources and compare their X-ray and gamma-ray properties to differentiate between the two source classes. We employ two machine-learning algorithms, decision tree and random forest (RF) classifier, to our high signal-to-noise ratio sample of 217 sources, each of which corresponds to Fermi unassociated regions. The accuracy scores for both methods were found to be 97% and 99%, respectively. The RF classifier, which is based on the application of a multitude of decision trees, associated a probability value (P bzr) for each source to be a blazar. This yielded 173 blazar candidates from this source sample, with P bzr ≥ 90% for each of these sources, and 134 of these possible blazar source associations had P bzr ≥ 99%. The results yielded 13 sources with P bzr ≤ 10%, which we deemed as reasonable candidates for pulsars, seven of which result with P bzr ≤ 1%. There were 31 sources that exhibited intermediate probabilities and were termed ambiguous due to their unclear characterization as a pulsar or a blazar.

Keywords: Gamma-ray sources, Blazars, X-ray sources, Pulsars
Deep Chandra Survey of the Small Magellanic Cloud. III. Formation Efficiency of High-mass X-Ray Binaries. We have compiled the most complete census of high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud with the aim to investigate the formation efficiency of young accreting binaries in its low-metallicity environment. In total, we use 123 X-ray sources with detections in our Chandra X-ray Visionary Program (XVP), supplemented by 14 additional (likely and confirmed) HMXBs identified by Haberl &amp; Sturm that fall within the XVP area, but are neither detected in our survey (nine sources) nor matched with any of the 127 sources identified in the XVP data (five sources). Specifically, we examine the number ratio of the HMXBs [N(HMXBs)] to (a) the number of OB stars, (b) the local star formation rate (SFR), and (c) the stellar mass produced during the specific star formation burst, all as a function of the age of their parent stellar populations. Each of these indicators serves a different role, but in all cases we find that the HMXB formation efficiency increases as a function of time (following a burst of star formation) up to ∼40-60 Myr, and then gradually decreases. The formation efficiency peaks at ∼30-40 Myr with average rates of {\text{}}{{N}}({HMXB})/{SFR}={339}-83+78 {({M}⊙ /{yr})}-1, and N(HMXB)/M \star =({8.74}-0.92+1.0)× {10}-6 {M}⊙ -1, in good agreement with previous estimates of the average formation efficiency in the broad ∼20-60 Myr age range.

Keywords: Early-type stars, Stellar ages, X-ray point sources, High mass x-ray binary stars, Star formation, Magellanic Clouds
Lorentz Factors of Compact Jets in Black Hole X-Ray Binaries. Compact, continuously launched jets in black hole X-ray binaries (BHXBs) produce radio to optical/IR synchrotron emission. In most BHXBs, an IR excess (above the disk component) is observed when the jet is present in the hard spectral state. We investigate why some BHXBs have prominent IR excesses and some do not, quantified by the amplitude of the IR quenching or recovery over the transition from/to the hard state. We find that the amplitude of the IR excess can be explained by inclination-dependent beaming of the jet synchrotron emission and the projected area of the accretion disk. Furthermore, we see no correlation between the expected and the observed IR excess for Lorentz factor 1, which is strongly supportive of relativistic beaming of the IR emission, confirming that the IR excess is produced by synchrotron emission in a relativistic outflow. Using the amplitude of the jet fade and recovery over state transitions and the known orbital parameters, we constrain for the first time the bulk Lorentz factor range of compact jets in several BHXBs (with all the well-constrained Lorentz factors lying in the range of Γ = 1.3-3.5). Under the assumption that the Lorentz factor distribution of BHXB jets is a power law, we find that N({{Γ }})\propto {{{Γ }}}-{1.88-0.34+0.27}. We also find that the very high amplitude IR fade/recovery seen repeatedly in the BHXB GX 339-4 favors a low inclination angle (≲ 15^\circ ) of the jet.

Keywords: Jets, Black holes, High energy astrophysics, Relativistic jets, Stellar mass black holes, Infrared astronomy, Infrared excess, Near infrared astronomy
A Submillimeter Perspective on the GOODS Fields (SUPER GOODS). IV. The Submillimeter Properties of X-Ray Sources in the CDF-S. The Chandra Deep Field (CDF)-S is the deepest X-ray image available and will remain so for the near future. We provide a spectroscopic (64.5%; 64% with spectral classifications) and photometric redshift catalog for the full 7 Ms sample, but much of our analysis focuses on the central (off-axis angles &lt;5.′7) region, which contains a large, faint ALMA sample of 75 &gt; 4.5σ 850 μm sources. We measure the 850 μm fluxes at the X-ray positions using the ALMA images, where available, or an ultradeep SCUBA-2 map. We find that the full X-ray sample produces ∼10% of the 850 μm extragalactic background light. We separate the submillimeter-detected X-ray sources into star-forming galaxies and active galactic nuclei (AGNs) using a star formation rate (SFR) versus X-ray luminosity calibration for high-SFR galaxies. We confirm this separation using the X-ray photon indices. We measure the X-ray fluxes at the accurate positions of the 75 ALMA sources and detect 70% at &gt;3σ in either the 0.5-2 or 2-7 keV bands. However, many of these may produce both their X-ray and submillimeter emission by star formation. Indeed, we find that only 20% of the ALMA sources have intermediate X-ray luminosities (rest-frame 8-28 keV luminosities of 1042.5-1044 erg s-1), and none has a high X-ray luminosity (&gt;1044 erg s-1). Conversely, after combining the CDF-S with the CDF-N, we find extreme star formation (SFR &gt; 300 M ☉ yr-1) in some intermediate X-ray luminosity sources but not in any high X-ray luminosity sources. We argue that the quenching of star formation in the most luminous AGNs may be a consequence of the clearing of gas in these sources.

Keywords: Cosmology, X-ray active galactic nuclei, Galaxy evolution, AGN host galaxies
Resolving the Interstellar Medium in Ultraluminous Infrared QSO Hosts with ALMA. We present ALMA observations of the CO(1-0) line and 3 mm continuum emission in eight ultraluminous infrared (IR) quasi-stellar objects (QSOs) at z = 0.06-0.19. All eight IR QSO hosts are clearly resolved in their CO molecular gas emission with a median source size of 3.2 kpc, and seven out of eight sources are detected in 3 mm continuum, which is found to be more centrally concentrated with respect to molecular gas with sizes of 0.4-1.0 kpc. Our observations reveal a diversity of CO morphology and kinematics for the IR QSO systems, which can be roughly classified into three categories: rotating gas disk with ordered velocity gradient, compact CO peak with disturbed velocity, and multiple CO distinct sources undergoing a merger between a luminous QSO and a companion galaxy separated by a few kpc. The molecular gas in three of the IR QSO hosts is found to be rotation-dominated with a ratio of the maximum rotation velocity to the local velocity dispersion of V rot/σ = 4-6. Basic estimates of the dynamical masses within the CO-emitting regions give masses between 7.4 × 109 and 6.9 × 1010 M ⊙. We find an increasing trend between black hole mass accretion rate and star formation rate (SFR) over 3 orders of magnitude in far-IR luminosity/SFR, in line with the correlation between QSO bolometric luminosity and star formation activity, indicative of a likely direct connection between active galactic nuclei and star formation activity over galaxy evolution timescales.

Keywords: AGN host galaxies, Starburst galaxies