adsabs/SciX_UAT_keywords huggingface dataset:
Kepler Binary Stars in the NGC 6819 Open Cluster: KIC 5113146 and KIC 5111815

In this study, an investigation of two double-lined binary stars KIC 5113146 and KIC 5111815 in the NGC 6819 open cluster is presented based on both photometric and spectroscopic data. Simultaneous analysis of light and radial velocity curves was made and the absolute parameters of the systems' components were determined for the first time. We find that both systems have F-type main-sequence components. The masses and radii were found to be M1 = 1.29 ± 0.02M⊙, R1 = 1.47 ± 0.03 ${R}_{\odot }$ and M2 = 1.19 ± 0.02 ${M}_{\odot }$ , R2 = 1.13 ± 0.02 ${R}_{\odot }$ for the primary and secondary components of KIC 5113146; and M1 = 1.51 ± 0.08 ${M}_{\odot }$ , R1 = 2.02 ± 0.05 ${R}_{\odot }$ and M2 = 1.19 ± 0.07 ${M}_{\odot }$ , R2 = 1.32 ± 0.04 ${R}_{\odot }$ for the components of KIC 5111815, respectively. The evolutionary status of the components was evaluated based on the MESA evolutionary tracks and isochrones. The ages of KIC 5111815 and KIC 5113146 were derived to be about 2.50 ± 0.35 Gyr and 1.95 ± 0.40 Gyr, respectively. Photometric distances were calculated to be 2850 ± 185 pc for KIC 5113146 and 3120 ± 260 pc for KIC 5111815. The results reveal that both KIC 5113146 and KIC 5111815 systems are the most likely members of NGC 6819.

Keywords: stellar astronomy; binary stars; detached binary stars; open star clusters
Searching for the Role of Mergers in Fast and Early SMBH Growth: Morphological Decomposition of Quasars and Their Hosts at z 4.8

We present rest-frame ultraviolet images of six luminous quasars at z ~ 4.8 obtained with the Hubble Space Telescope (HST). These quasars exhibit a wide range of star formation rates (SFRs) and lie in a wide range of environments. We carefully model and subtract the point-like quasar emission and investigate the morphology of the underlying host galaxies at kpc scales. The residual images allowed identification of potential companion sources, which enabled us to explore the role of galaxy merger scenarios in the coevolution of the quasars and their hosts. We also search for the mechanism driving extreme SFRs in three of the six quasars. We find that the rate of detection of potential companions to the host galaxies does not follow trends between high- and low-SFR sources; i.e., the HST imaging suggests that both high- and low-SFR sources are found in both dense and sparse galactic environments. The suggested role of major mergers driving extreme SFRs cannot be supported by the multiwavelength data in hand. Three of four companion sources, previously revealed by submillimeter observations, are not detected in the HST images of three of our quasars. An adapted high-resolution imaging strategy focused on high-SFR sources and extended to a larger quasar sample is required in order to determine the role of mergers in the processes of star formation and supermassive black hole growth at high redshift.

Keywords: supermassive black holes; quasars; galaxy mergers; agn host galaxies; star formation
Orbital Distribution of Infalling Satellite Halos across Cosmic Time

The initial orbits of infalling subhalos largely determine the subsequent evolution of the subhalos and satellite galaxies therein and shed light on the assembly of their hosts. Using a large set of cosmological simulations of various resolutions, we quantify the orbital distribution of subhalos at infall time and its mass and redshift dependence in a large dynamic range. We further provide a unified and accurate model validated across cosmic time, which can serve as the initial condition for semianalytic models. We find that the infall velocity v follows a nearly universal distribution peaked near the host virial velocity Vh for any subhalo mass or redshift, while the infall orbit is most radially biased when v ∼ Vh. Moreover, subhalos that have a higher host mass or a higher sub-to-host ratio tend to move along a more radial direction with a relatively smaller angular momentum than their low host mass or low sub-to-host ratio counterparts, though they share the same normalized orbital energy. These relations are nearly independent of the redshift when using the density peak height as the proxy for host halo mass. The above trends are consistent with the scenario where the dynamical environment is relatively colder for more massive structures because their own gravity is more likely to dominate the local potentials. Based on this understanding, the more massive or isolated halos are expected to have higher velocity anisotropy.

Keywords: dark matter; galaxy dark matter halos; galaxy kinematics; galaxy dynamics; large-scale structure of the universe; n-body simulations; astrostatistics; galaxy formation
FRBs Lensed by Point Masses I. Lens Mass Estimation for Doubly Imaged FRBs

Fast radio bursts (FRBs) are bright radio transient events with durations on the order of milliseconds. The majority of FRB sources discovered so far have a single peak, with the exception of a few showing multiple-peaked profiles, the origin of which is unknown. In this work, we show that the strong lensing effect of a point mass or a point mass + external shear on a single-peak FRB can produce double peaks (i.e., lensed images). In particular, the leading peak will always be more magnified and hence brighter than the trailing peak for a point-mass lens model, while the point-mass + external shear lens model can produce a less magnified leading peak. We find that, for a point-mass lens model, the combination of lens mass M and redshift zl in the form of M(1 + zl) can be directly computed from two observables—the delayed time Δt and the flux ratio of the leading peak to the trailing peak R. For a point-mass + external shear lens model, upper and lower limits in M(1 + zl) can also be obtained from Δt and R for a given external shear strength. In particular, tighter lens mass constraints can be achieved when the observed R is larger. Lastly, we show the process of constraining lens mass using the observed values of Δt and R of two double-peaked FRB sources, i.e., FRB 121002 and FRB 130729, as references, although the double-peaked profiles are not necessarily caused by strong lensing.

Keywords: cosmology; gravitational lensing
ALMA Observations of CO Emission from Luminous Lyman-break Galaxies at z = 6.0293-6.2037

We present our new Atacama Large Millimeter/submillimeter Array (ALMA) observations targeting CO(6-5) emission from three luminous Lyman-break galaxies (LBGs) at z spec = 6.0293-6.2037 found in the Subaru/Hyper Suprime-Cam survey, whose [O III] 88 μm and [C II] 158 μm emissions have been detected with ALMA. We find a marginal detection of the CO(6-5) line from one of our LBGs, J0235-0532, at the ≃4σ significance level and obtain upper limits for the other two LBGs, J1211-0118 and J0217-0208. Our z = 6 luminous LBGs are consistent with the previously found correlation between the CO luminosity and the infrared luminosity. The unique ensemble of the multiple far-infrared emission lines and underlying continuum fed to a photodissociation region model reveals that J0235-0532 has a relatively high density of hydrogen nuclei n H that is comparable to those of low-z (U)LIRGs, quasars, and Galactic star-forming regions with high n H values, while the other two LBGs have lower n H consistent with local star-forming galaxies. By carefully taking account of various uncertainties, we obtain constraints on total gas mass and gas surface density from their CO luminosity measurements. We find that J0235-0532 is located below the Kennicutt-Schmidt (KS) relation, comparable to the z = 5.7 LBG, HZ10, previously detected with CO(2-1). Combined with previous results for dusty starbursts at similar redshifts, the KS relation at z = 5-6 is on average consistent with the local one.

Keywords: millimeter astronomy; submillimeter astronomy; high-redshift galaxies; galactic and extragalactic astronomy; galaxy formation; galaxy evolution; photodissociation regions; interstellar medium; molecular gas; interstellar line emission; co line emission; lyman-break galaxies
Dust Reverberation of 3C 273: Torus Structure and Lag-Luminosity Relation

We monitored the z = 0.158 quasar 3C 273 between 2015 and 2019 in the optical (BVrz) and near-infrared (JHK) with the aim to perform dust reverberation mapping. Accounting for host galaxy and accretion disk contributions, we obtained pure dust light curves in JHK. Cross correlations between the V band and the dust light curves yield an average rest-frame delay for the hot dust of τcent ∼ 410 days. This is a factor of two shorter than that expected from the the dust ring radius Rx ∼ 900 lt-day reported from interferometric studies. The dust covering factor (CF) is about 8%, much smaller than that predicted from the half covering angle of 45° found for active galactic nuclei (AGNs). We analyze the asymmetric shape of the correlation functions and explore whether an inclined biconical bowl-shaped dust torus geometry could bring these findings (τcent, Rx and CF) into a consistent picture. The hot varying dust emission originates from the edge of the bowl rim with a small covering angle 40° < θ < 45°, and we see only the near side of the biconus. Such a dust gloriole with Rx = 900 ± 200 lt-day and an inclination 12° matches the data remarkably well. Comparing the results of 3C 273 with literature for less luminous AGN, we find a lag-luminosity relation τ ∝ Lα with α = 0.33-0.40, flatter than the widely adopted relation with α ∼ 0.5. We address several explanations for the new lag-luminosity relation.

Keywords: reverberation mapping; active galactic nuclei; photometry; quasars
Isomers in Interstellar Environments. I. The Case of Z- and E-cyanomethanimine

In this work, we present the results of our investigation into the chemistry of Z- and E-cyanomethanimine (HNCHCN), both of which are possible precursors to the nucleobase adenine. Ab initio quantum chemical calculations for a number of reactions with atomic hydrogen were carried out. We find that the reaction H + Z/E-HNCHCN leading both to H-addition as well as H2-abstraction proceed via similar short-range barriers with bimolecular rate coefficients on the order of ∼10-17 cm3 s-1. These results were then incorporated into astrochemical models and used in simulations of the giant molecular cloud G+0.693. The calculated abundances obtained from these models were compared with previous observational data and found to be in good agreement, with a predicted [Z/E] ratio of ∼3—somewhat smaller than the previously derived value of 6.1 ± 2.4. We find that the [Z/E] ratio in our simulations is due mostly to ion-molecule destruction rates driven by the different permanent dipoles of the two conformers. Based on these results, we propose a general rule-of-thumb for estimating the abundances of isomers in interstellar environments, which we call the "relative dipole principle."

Keywords: molecule destruction; giant molecular clouds; galactic center; pre-biotic astrochemistry; astrochemistry; interstellar molecules
Coherent Time-domain Canceling of Interference for Radio Astronomy

Radio astronomy is vulnerable to interference from a variety of anthropogenic sources. Among the many strategies for mitigation of this interference is coherent time-domain canceling (CTC), which ideally allows one to "look through" interference, as opposed to avoiding the interference or deleting the afflicted data. However, CTC is difficult to implement, not well understood, and at present this strategy is not in regular use at any major radio telescope. This paper presents a review of CTC including a new comprehensive study of the capabilities and limitations of CTC using metrics relevant to radio astronomy, including fraction of interference power removed and increase in noise. This work is motivated by the emergence of a new generation of communications systems which pose a significantly increased threat to radio astronomy and which may overwhelm mitigation methods now in place.

Keywords: radio telescopes; astronomy data analysis; astronomical instrumentation
TOI-824 b: A New Planet on the Lower Edge of the Hot Neptune Desert

We report the detection of a transiting hot Neptune exoplanet orbiting TOI-824 (SCR J1448-5735), a nearby (d = 64 pc) K4V star, using data from the Transiting Exoplanet Survey Satellite. The newly discovered planet has a radius Rp = 2.93 ± 0.20 ${R}_{\oplus }$ and an orbital period of 1.393 days. Radial velocity measurements using the Planet Finder Spectrograph and the High Accuracy Radial velocity Planet Searcher spectrograph confirm the existence of the planet, and we estimate its mass to be 18.47 ± 1.84 ${M}_{\oplus }$ . The planet's mean density is ${\rho }_{{\rm{p}}}$ = 4.03 ${}_{-0.78}^{+0.98}$ ${\rm{g}}\,{\mathrm{cm}}^{-3}$ , making it more than twice as dense as Neptune. TOI-824 b's high equilibrium temperature makes the planet likely to have a cloud-free atmosphere, and thus it is an excellent candidate for follow-up atmospheric studies. The detectability of TOI-824 b's atmosphere from both ground and space is promising and could lead to the detailed characterization of the most irradiated small planet at the edge of the hot Neptune desert that has retained its atmosphere to date.

Keywords: exoplanet astronomy; exoplanet detection methods; exoplanets; transit photometry; radial velocity; stellar properties
Variability Signatures of a Burst Process in Flaring Gamma-Ray Blazars

Blazars exhibit stochastic flux variability across the electromagnetic spectrum, often exhibiting heavy-tailed flux distributions, commonly modeled as lognormal. However, Tavecchio et al. and Adams et al. found that the high-energy gamma-ray flux distributions of several of the brightest flaring Fermi-LAT flat-spectrum radio quasars (FSRQs) are well modeled by an even heavier-tailed distribution, which we show is the inverse gamma distribution. We propose an autoregressive inverse gamma variability model in which an inverse gamma flux distribution arises as a consequence of a shot-noise process. In this model, discrete bursts are individually unresolved and averaged over within time bins, as in the analysis of Fermi-LAT data. Stochastic variability on timescales longer than the time-bin duration is modeled using first-order autoregressive structure. The flux distribution becomes approximately lognormal in the limiting case of many weak bursts. The fractional variability is predicted to decrease as the time-bin duration increases. Using simulated light curves, we show that the proposed model is consistent with the typical gamma-ray variability properties of FSRQs and BL Lac objects. The model parameters can be physically interpreted as the average burst rate, the burst fluence, and the timescale of long-term stochastic fluctuations.

Keywords: blazars; flat-spectrum radio quasars; bl lacertae objects; gamma-ray astronomy; time series analysis; time domain astronomy; active galactic nuclei
The Behavior of Bp He-weak Stars in the Far UV-Paper VII: HD 144334

The analysis of 14 spectra of the B8 He-weak Si star HD 144334 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution shortwards of 1600 Å over a time interval of about five days in 1994 October. In contrast, the level of the mid-UV flux did 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.

Keywords: chemically peculiar stars; helium-weak stars
TIMES. I. A Systematic Observation in Multiple Molecular Lines toward the Orion A and Ophiuchus Clouds

We have used the Taeduk Radio Astronomy Observatory to observe the Orion A and Ophiuchus clouds in the J = 1-0 lines of 13CO, C18O, HCN, HCO+, and N2H+ and the J = 2-1 line of CS. The fully sampled maps with uniform noise levels are used to create moment maps. The variations of the line intensity and velocity dispersion with total column density, derived from dust emission maps, are presented and compared to previous work. The CS line traces dust column density over more than one order of magnitude, and the N2H+ line best traces the highest column density regime ( $\mathrm{log}({N}_{{{\rm{H}}}_{2}}$ ) > 22.8). Line luminosities, integrated over the cloud, are compared to those seen in other galaxies. The HCO+-to-HCN luminosity ratio in the Orion A cloud is similar to that of starburst galaxies, while that in the Ophiuchus cloud is in between those of active galactic nuclei and starburst galaxies.

Keywords: molecular clouds
2016 Outburst of H 1743-322: XMM-Newton and NuSTAR View

We report the detection of a type C quasi-periodic oscillation (QPO) along with an upper harmonic in the commensurate ratio of 1:2 in two observations of the low-mass black hole transient H 1743-322 jointly observed by XMM-Newton and NuSTAR during the 2016 outburst. We find that the QPO and the upper harmonic exhibit shifts in their centroid frequencies in the second observation with respect to the first one. The hardness intensity diagram implies that in contrast to the 2008 and 2014 failed outbursts, the 2016 outburst was a successful one. We also detect the presence of a broad iron Kα line at ∼6.5 keV and a reflection hump in the energy range 15-30 keV in both of the observations. Along with the shape of the power density spectra, the nature of the characteristic frequencies and the fractional rms amplitude of the timing features imply that the source stayed in the low/hard state during these observations. Moreover, the photon index and other spectral parameters also indicate the low/hard state behavior of the source. Unlike the soft lag detected in this source during the 2008 and 2014 failed outbursts, we observe hard time lags of 0.40 ± 0.15 s and 0.32 ± 0.07 s in the 0.07-0.4 Hz frequency range in the two observations during the 2016 outburst. The correlation between the photon index and the centroid frequency of the QPO is consistent with the previous results. Furthermore, the high value of the Comptonized fraction and the weak thermal component indicate that the QPO is being modulated by the Comptonization process.

Keywords: high energy astrophysics; low-mass x-ray binary stars; stellar mass black holes
In Situ Star Formation in Accretion Disks and Explanation of Correlation between the Black Hole Mass and Metallicity in Active Galactic Nuclei

Recent observations show that the metallicity Z BLR of the broad-line region (BLR) in active galactic nuclei (AGNs) is solar to supersolar, which is positively correlated with the mass of supermassive black holes (M BH) and does not evolve with the redshift up to z ~ 7. We revisit the M BH-Z BLR correlation with more AGNs with M BH ~ 106-8 M ⊙ and find that the positive correlation becomes flat in the low-mass range. It is known that the outer part of accretion disks is gravitationally unstable and can fragment into stars. Considering the star formation and supernovae in the outer AGN disk, we calculate the metal enrichment and find that the positive M BH-Z BLR correlation can be roughly reproduced if the stellar mass distribution is "top heavy." We find that the observed BLR size is more or less similar to the self-gravity radius of the AGN disk, which suggests that the BLR may be closely correlated with the underlying accretion process.

Keywords: high-luminosity active galactic nuclei; galaxy accretion; metallicity; star formation
Circumgalactic Lyα Nebulae in Overdense Quasar Pair Regions Observed with the Palomar Cosmic Web Imager

The recent discovery of enormous Lyα nebulae (ELANe), characterized by physical extents >200 kpc and Lyα luminosities >1044 erg s-1, provides a unique opportunity to study the intergalactic medium and circumgalactic medium in distant galaxies. Many existing ELANe detections are associated with local overdensities of active galactic nuclei (AGN). We have initiated a search for ELANe around regions containing pairs of quasi-stellar objects (QSOs) using the Palomar Cosmic Web Imager. The first study of this search, Cai et al., presented results of ELAN0101+0201, which was associated with a QSO pair at z = 2.45. In this study, all targets residing in QSO pair environments analyzed have Lyα detections, but only one of the four targets meets the classification criteria of an ELANe associated with a QSO pair region (z ~ 2.87). The other three sample detections of Lyα nebulae do not meet the size and luminosity criteria to be classified as ELANe. We find kinematic evidence that the ELANe J1613 is possibly powered mostly by AGN outflows. The analysis of circularly averaged surface brightness profiles of emission from the Lyα regions shows that the Lyα emission around z ~ 2 QSO pairs is consistent with emission around individual QSOs at z ~ 2, which is fainter than that around z ~ 3 QSOs. A larger sample of Lyα at z ~ 2 will be needed to determine if there is evidence of redshift evolution when compared to nebular emissions at z ~ 3 from other studies.

Keywords: quasars; galaxy evolution; emission nebulae; lyman-alpha galaxies; quasar-galaxy pairs; galaxy spectroscopy; active galactic nuclei; spectroscopy; active galaxies; nebulae; intergalactic medium
Detection of Al II in the Ultraviolet Spectra of Metal-poor Stars: An Empirical LTE Test of NLTE Aluminum Abundance Calculations

We report the detection of an Al II line at 2669.155 Å in 11 metal-poor stars, using ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We derive Al abundances from this line using a standard abundance analysis, assuming local thermodynamic equilibrium (LTE). The mean [Al/Fe] ratio is -0.06 ± 0.04 (σ = 0.22) for these 11 stars spanning - 3.9 < [Fe/H] < -1.3, or [Al/Fe] = -0.10 ± 0.04 (σ = 0.18) for 9 stars spanning -3.0 < [Fe/H] < -1.3 if two carbon-enhanced stars are excluded. We use these abundances to perform an empirical test of non-LTE (NLTE) abundance corrections predicted for resonance lines of Al I, including the commonly used optical Al I line at 3961 Å. The Al II line is formed in LTE, and the abundance derived from this line matches that derived from high-excitation Al I lines predicted to have minimal NLTE corrections. The differences between the abundance derived from the Al II line and the LTE abundance derived from Al I resonance lines are +0.4 to +0.9 dex, which match the predicted NLTE corrections for the Al I resonance lines. We conclude that the NLTE abundance calculations are approximately correct and should be applied to LTE abundances derived from Al I lines. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. The data presented in this paper were obtained from the Barbara A. Mikulski Archive for Space Telescopes. Other data have been obtained from the European Southern Observatory Science Archive Facility. This research has also made use of the Keck Observatory Archive, which is operated by the W.M. Keck Observatory and the NASA Exoplanet Science Institute, under contract with NASA. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin, and the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: nucleosynthesis; stellar abundances; stellar atmospheres; ultraviolet astronomy