adsabs/SciX_UAT_keywords huggingface dataset:
The Effect of the Angular Momentum in the Formation and Evolution of Low Surface Brightness Galaxies

Using observed data from the literature, we compare in one single publication the angular momentum (AM) of low surface brightness galaxies (LSBGs), with that of high surface brightness galaxies (HSBGs), a comparison that either is currently spread across many unconnected references, or simply does not exist. Partly because of the subject, this has received little attention outside the realm of simulations. We use previous results of the stellar specific AM j* from the SPARC database containing Spitzer 3.6 μm photometry and accurate H I rotation curves from Lelli et al. using a sample of 38 LSBGs and 82 HSBGs. We do this with the objective of comparing both galaxy populations, finding that LSBGs are higher in the Fall relation by about 0.174 dex. Additionally, we apply and test different masses and formation models to estimate the spin parameter λ, which quantifies the rotation obtained from the tidal torque theory, finding no clear evidence of a difference in the spin of LSBGs and HSBGs under a classic disk formation model that assumes the ratio (fj) between j* and the specific AM of the halo is ~1. In another respect, by using the biased collapse model, where fj depends on the star formation efficiency, it was found that LSBGs clearly show higher spin values, having an average spin of ~2 times the average spin of HSBGs. This latter result is consistent with those obtained from simulations by Dalcanton et al.

Keywords: galaxy evolution; galaxy formation; galaxy dark matter halos; galaxy kinematics; galaxy dynamics; low surface brightness galaxies; galaxy rotation; galaxy rotation curves
Transition Probabilities of Near-infrared Ce III Lines from Stellar Spectra: Applications to Kilonovae

Kilonova spectra provide us with information of r-process nucleosynthesis in neutron star mergers. However, it is still challenging to identify individual elements in the spectra mainly due to the lack of experimentally accurate atomic data for heavy elements at near-infrared wavelengths. Recently, Domoto et al. proposed that the absorption features around 14500 Å in the observed spectra of GW170817/AT2017gfo are Ce III lines. But they used theoretical transition probabilities (gf-values) whose accuracy is uncertain. In this paper, we derive the astrophysical gf-values of three Ce III lines, aiming at verifying this identification. We model high-resolution H-band spectra of four F-type supergiants showing clear Ce III absorption features by assuming stellar parameters derived from optical spectra in the literature. We also test the validity of the derived astrophysical gf-values by estimating the Ce III abundances of Ap stars. We find that the derived astrophysical gf-values of the Ce III lines are systematically lower by about 0.25 dex than those used in previous work of kilonovae, while they are still compatible within the uncertainty ranges. By performing radiative transfer simulations of kilonovae with the derived gf-values, we find that the identification of Ce III as a source of absorption features in the observed kilonova spectra still stands, even considering the uncertainties in the astrophysical gf-values. This supports the identification of Ce in the spectra of GW170817/AT2017gfo.

Keywords: r-process; radiative transfer simulations; transition probabilities
The Spin-down Accretion Regime of Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

The relatively high fluxes of the Galactic ultraluminous X-ray pulsar Swift J0243 allow a detailed study of its spin-down regime in the quiescent state for the first time. After the 2017 giant outburst, its spin frequency shows a linearly decreasing trend with some variations due to minor outbursts. The linear spin-down rate is ~ -1.9 × 10-12 Hz s-1 during the period of lowest luminosity, from which one can infer a dipole field of ~1.75 × 1013 G. The $\dot{\nu }\mbox{--}L$ relation during the spin-down regime is complex, and $\dot{\nu }$ is close to zero when the luminosity reaches both the high end (L 38 ~ 0.3) and the lowest value (L 38 ~ 0.03). The luminosity of zero torque is different for the giant outburst and other minor outbursts. This is likely due to different accretion flows for different types of outburst, as evidenced by the differences in the spectra and pulse profiles at a similar luminosity for different types of outburst (giant or not). The pulse profile changes from double peaks in the spin-up state to a single broad peak in the low spin-down regime, indicating the emission beam/region is larger in the low spin-down regime. These results show that accretion is still ongoing in the low spin-down regime, for which the neutron star is supposed to be in a propeller state.

Keywords: high mass x-ray binary stars
The Ultraluminous X-Ray Sources Population of the Galaxy NGC 7456

Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 1039 erg s-1. The ULX population counts several hundred objects but only a fraction are well studied. Here we present a detailed analysis of all ULXs hosted in the galaxy NGC 7456. It was observed in X-rays only once in the past (in 2005) by XMM-Newton. but the observation was short and strongly affected by high background. In 2018, we obtained a new, deeper (∼90 ks) XMM-Newton observation that allowed us to perform a detailed characterization of the ULXs hosted in the galaxy. ULX-1 and ULX-2, the two brightest objects (LX ∼ 6-10 × 1039 erg s-1), have spectra that can be described by a model with two thermal components, as often found in ULXs. ULX-1 also shows one order of magnitude in flux variability on short-term timescales (hundreds to thousands of kiloseconds). The other sources (ULX-3 and ULX-4) show flux changes of at least an order of magnitude, and these objects may be candidate transient ULXs, although longer X-ray monitoring or further studies are required to ascribe them to the ULX population. In addition, we found a previously undetected source that might be a new candidate ULX (labeled as ULX-5), with a luminosity of ∼1039 erg s-1 and hard power-law spectral shape, whose nature is still unclear and for which a background active galactic nucleus cannot be excluded. We discuss the properties of all the ULXs in NGC 7456 within the framework of super-Eddington accretion onto stellar-mass compact objects. Although no pulsations were detected, we cannot exclude that the sources host neutron stars.

Keywords: x-ray astronomy; x-ray binary stars; x-ray sources; neutron stars; pulsars
The Planetary Accretion Shock. III. Smoothing-free 2.5D Simulations and Calculation of Hα Emission

Surveys have looked for Hα emission from accreting gas giants but found very few objects. Analyses of the detections and nondetections have assumed that the entire gas flow feeding the planet is in radial freefall. However, hydrodynamical simulations suggest that this is far from reality. We calculate the Hα emission from multidimensional accretion onto a gas giant, following the gas flow from Hill sphere scales down to the circumplanetary disk (CPD) and the planetary surface. We perform azimuthally symmetric radiation hydrodynamics simulations around the planet and use modern tabulated gas and dust opacities. Crucially, contrasting with most previous simulations, we do not smooth the gravitational potential but do follow the flow down to the planetary surface, where grid cells are 0.01 Jupiter radii small. We find that roughly only 1% of the net gas inflow into the Hill sphere directly reaches the planet. As expected for ballistic infall trajectories, most of the gas falls at too large a distance on the CPD to generate Hα. Including radiation transport removes the high-velocity subsurface flow previously seen in hydrodynamics-only simulations, so that only the free planet surface and the inner regions of the CPD emit substantial Hα. Unless magnetospheric accretion, which we neglect here, additionally produces Hα, the corresponding Hα production efficiency is much smaller than usually assumed, which needs to be taken into account when analyzing (non)detection statistics.

Keywords: accretion; radiative transfer; hydrodynamical simulations; shocks; planet formation; h alpha photometry
Comparison of Convolutional Neural Networks and Random Forest Classifiers for Strong Gravitational Lens Identification

Strong gravitational lenses have been instrumental in providing insight into various astronomical problems, including analyzing the dark matter distribution of the universe. Effective identification of these events is made possible through machine learning algorithms, with many recent studies focusing on neural networks. However, very few have investigated the tradeoffs between different algorithms besides neural networks for lens identification. Our paper compares a convolutional neural network (CNN) and a random forest classifier (RFC) to determine the benefits of each for this task. We find that while CNNs do achieve higher accuracy, using RFCs to supplement them could increase the effectiveness of such algorithms. As a result, models that utilize both side-by-side to make predictions may increase in accuracy. This should be explored by future research.

Keywords: strong gravitational lensing; optical identification
Nuclear Structures of 17O and Time-dependent Sensitivity of the Weak s-process to the 16O(n,γ)17O Rate

We revisit the radiative neutron capture reaction 16O(n,γ)17O of astrophysical interest, based on the new reevaluated cross-section data. Several potentials are proposed to predict direct capture cross sections. The contributions from single-particle resonances to total capture cross section are quantitatively considered in Breit-Wigner formalism, taking into account the interference term between direct capture and resonant cross sections, which is crucial for the description of the behavior around the resonance energies. A new cross section is achieved based upon χ2-fittings for optimized resonance parameters using Minuit code, and it has a largely improved agreement with updated experimental data. Statistical errors are also evaluated for the total and Maxwellian-averaged cross sections. It is confirmed that the direct captures dominate the total cross sections; however, resonant contribution also becomes progressively more important as the energy increases to 100 keV. Resonance contribution can increase the reaction rates for energy region 50 keV < E < 100 keV by 5% ± 5%-25% ± 5%, and around 8% ± 5% in comparison with KADoNiS v0.3 rate and the latest data evaluations, respectively. We show a detailed propagation of the uncertainty in the 16O(n,γ) reaction rate to abundances of nuclei, including s-nuclei during the weak s-process with a multi-zone nuclear network calculation. Although an enhanced rate of 16O(n,γ) diminishes the s-process efficiency in the 25 M⊙ stellar model adopted from the Modules for Experiments in Stellar Astrophysics, it can lead to larger abundances of neutrons as well as 22Ne in the late epoch of C burning.

Keywords: helium burning; reaction rates; s-process; massive stars
On the Effects of Local Environment on Active Galactic Nucleus (AGN) in the Horizon Run 5 Simulation

We use the Horizon Run 5 cosmological simulation to study the effect of galaxy intrinsic properties and the local environment on active galactic nuclei (AGNs) characterized by their threshold of the accretion rate. We select galaxies in the stellar mass range ${10}^{9.5}\leqslant {M}_{* }^{}/{M}_{\odot }^{}\leqslant {10}^{10.5}$ in the snapshot at redshift z = 0.625. Among various intrinsic properties, we find that the star formation rate of the host galaxy is most correlated to the AGN activity. To quantify the environment, we use background galaxy number density (large-scale environment) and distance and morphological type of the nearest neighbors (small-scale environment), and study their relative effects on the AGN properties. We find that, compared to the background density, the nearest neighbor environment is the dominant quantity determining the bolometric luminosity, star formation rate, and kinematic properties of AGNs and better dictates the gas mass of the host galaxy. We show that the cold gas content in the host galaxies is crucial in triggering AGN activity. However, when the nearest neighbor environment effects start to act at the neighbor distance of less than about half the virial radius of the neighbor, the neighbor environmental effects are the most dominant factor for quasar activity.

Keywords: galaxy environments; agn host galaxies; galaxy encounters; galaxy interactions
Wide-band Timing of the Parkes Pulsar Timing Array UWL Data

In 2018 an ultra-wide-bandwidth low-frequency (UWL) receiver was installed on the 64 m Parkes Radio Telescope, enabling observations with an instantaneous frequency coverage from 704 to 4032 MHz. Here we present the analysis of a 3 yr data set of 35 ms pulsars observed with the UWL by the Parkes Pulsar Timing Array, using wide-band timing methods. The two key differences compared to typical narrowband methods are (1) generation of two-dimensional templates accounting for pulse shape evolution with frequency and (2) simultaneous measurements of the pulse time of arrival (TOA) and dispersion measure (DM). This is the first time that wide-band timing has been applied to a uniform data set collected with a single large fractional bandwidth receiver, for which such techniques were originally developed. As a result of our study, we present a set of profile evolution models and new timing solutions, including initial noise analysis. Precision of our TOA and DM measurements is in the range of 0.005-2.08 μs and (0.043-14.24) × 10-4 cm-3 pc, respectively, with 94% of the pulsars achieving a median TOA uncertainty of less than 1 μs.

Keywords: pulsar timing method; millisecond pulsars
Gamma-Ray Eclipses and Orbital Modulation Transitions in the Candidate Redback 4FGL J1702.7-5655

Observations with the Fermi Large Area Telescope (LAT) of the gamma-ray source 4FGL J1702.7-5655, previously classified as a candidate millisecond pulsar, show highly significant modulation at a period of 0.2438033 days (~5.85 hr). Further examination of the folded light curve indicates the presence of narrow eclipses, suggesting that this is a redback binary system. An examination of the long-term properties of the modulation over 13 years of LAT observations indicates that the orbital modulation of the gamma rays changed from a simple eclipse before early 2013 to a broader, more easily detected quasi-sinusoidal modulation. In addition, the time of the eclipse shifts to ~0.05 later in phase. This change in the orbital modulation properties, however, is not accompanied by a significant overall change in gamma-ray flux or spectrum. The quasi-sinusoidal component peaks ~0.5 out of phase with the eclipse, which would indicate inferior conjunction of the compact object in the system. Swift X-ray Telescope observations reveal a possible X-ray counterpart within the LAT error ellipse. However, radio observations obtained with the Australia Telescope Compact Array do not detect a source in the region. 4FGL J1702.7-5655 appears to have changed its state in 2013, perhaps related to changes in the intrabinary shock in the system. We compare the properties of 4FGL J1702.7-5655 to those of other binary millisecond pulsars that have exhibited orbital modulation in gamma-rays.

Keywords: gamma-ray sources; low-mass x-ray binary stars; millisecond pulsars; neutron stars; eclipsing binary stars
Protoplanetary Disks in the Orion Nebula Cluster: Gas-disk Morphologies and Kinematics as Seen with ALMA

We present Atacama Large Millimeter Array CO(3 - 2) and HCO+(4 - 3) observations covering the central 1'5 × 1'5 region of the Orion Nebula Cluster (ONC). The unprecedented level of sensitivity (∼0.1 mJy beam-1) and angular resolution (∼0"09 ≈ 40 au) of these line observations enable us to search for gas-disk detections toward the known positions of submillimeter-detected dust disks in this region. We detect 23 disks in gas: 17 in CO(3 - 2), 17 in HCO+(4 - 3), and 11 in both lines. Depending on where the sources are located in the ONC, we see the line detections in emission, in absorption against the warm background, or in both emission and absorption. We spectrally resolve the gas with 0.5 km s-1 channels and find that the kinematics of most sources are consistent with Keplerian rotation. We measure the distribution of gas-disk sizes and find typical radii of ∼50-200 au. As such, gas disks in the ONC are compact in comparison with the gas disks seen in low-density star-forming regions. Gas sizes are universally larger than the dust sizes. However, the gas and dust sizes are not strongly correlated. We find a positive correlation between gas size and distance from the massive star θ1 Ori C, indicating that disks in the ONC are influenced by photoionization. Finally, we use the observed kinematics of the detected gas lines to model Keplerian rotation and infer the masses of the central pre-main-sequence stars. Our dynamically derived stellar masses are not consistent with the spectroscopically derived masses, and we discuss possible reasons for this discrepancy.

Keywords: protoplanetary disks; circumstellar disks; proplyds; circumstellar gas; young star clusters; young stellar objects; pre-main sequence stars; planet formation; radio astronomy; millimeter astronomy
Early Planet Formation in Embedded Disks (eDisk). XII. Accretion Streamers, Protoplanetary Disk, and Outflow in the Class I Source Oph IRS 63

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Class I source Oph IRS 63 in the context of the Early Planet Formation in Embedded Disks large program. Our ALMA observations of Oph IRS 63 show a myriad of protostellar features, such as a shell-like bipolar outflow (in 12CO), an extended rotating envelope structure (in 13CO), a streamer connecting the envelope to the disk (in C18O), and several small-scale spiral structures seen toward the edge of the dust continuum (in SO). By analyzing the velocity pattern of 13CO and C18O, we measure a protostellar mass of M ⋆ = 0.5 ± 0.2 M ⊙ and confirm the presence of a disk rotating at almost Keplerian velocity that extends up to ~260 au. These calculations also show that the gaseous disk is about four times larger than the dust disk, which could indicate dust evolution and radial drift. Furthermore, we model the C18O streamer and SO spiral structures as features originating from an infalling rotating structure that continuously feeds the young protostellar disk. We compute an envelope-to-disk mass infall rate of ~10-6 M ⊙ yr-1 and compare it to the disk-to-star mass accretion rate of ~10-8 M ⊙ yr-1, from which we infer that the protostellar disk is in a mass buildup phase. At the current mass infall rate, we speculate that soon the disk will become too massive to be gravitationally stable.

Keywords: protoplanetary disks; protostars; stellar accretion; low mass stars; star formation; planet formation
Standardized Luminosity of the Tip of the Red Giant Branch Utilizing Multiple Fields in NGC 4258 and the CATs Algorithm

The tip of the red giant branch provides a luminous standard candle for calibrating distance ladders that reach Type Ia supernova (SN Ia) hosts. However, recent work reveals that tip measurements vary at the ~0.1 mag level for different stellar populations and locations within a host, which may lead to inconsistencies along the distance ladder. We pursue a calibration of the tip using 11 Hubble Space Telescope fields around the maser host, NGC 4258, that is consistent with SN Ia hosts by standardizing tip measurements via their contrast ratios. We find F814W-band tips that exhibit a full 0.3 mag range and 0.1 mag dispersion. We do not find any correlation between H I column density and the apparent tip to 0.04 ± 0.03 mag/cm-2. We search for a tip-contrast relation (TCR) and measure the TCR within the fields of NGC 4258 of -0.015 ± 0.008 mag/R, where R is the contrast ratio. This value is consistent with the TCR originally discovered in the GHOSTS sample of -0.023 ± 0.005 mag/R. Combining these measurements, we find a global TCR of -0.021 ± 0.004 mag/R and a calibration of ${M}_{I}^{\mathrm{TRGB}}=-4.025\pm 0.035-(R-4)\times 0.021$ mag. We also use stellar models to simulate single age and metallicity stellar populations with [Fe/H] from -2.0 to -0.7 and ages from 3 to 12 Gyr and reconstruct the global TCR found here to a factor of ~2. This work is combined in a companion analysis with tip measurements of nearby SN Ia hosts to measure H 0.

Keywords: red giant stars; standard candles; stellar distance; hubble constant; observational cosmology; calibration; absolute magnitude; luminosity function; red giant tip; distance indicators
Heated Poles on the Companion of Redback PSR J2339-0533

We analyze the photometry and spectra of the "redback" millisecond pulsar binary J2339-0533. These observations include new measurements from Keck and the Gamma-Ray Burst Optical/Near-infrared Detector (GROND), as well as archival measurements from the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER), WIYN, Southern Astrophysical Research (SOAR), and Hobby-Eberly Telescope (HET) telescopes. The parameters derived from GROND, our primary photometric data, describe well the rest of the data sets, raising our confidence in our fitted binary properties. Our fit requires hot spots (likely magnetic poles) on the surface of the companion star, and we see evidence that these spots move over the 8 yr span of our photometry. The derived binary inclination i = 69°3 ± 2°3, together with the center-of-mass velocity (from the radial-velocity fits) KC = 347.0 ± 3.7 $\mathrm{km}\,{{\rm{s}}}^{-1}$ , give a fairly typical neutron star mass of 1.47 ± 0.09 M⊙.

Keywords: pulsars
No Evidence for Orbital Clustering in the Extreme Trans-Neptunian Objects

The apparent clustering in longitude of perihelion ϖ and ascending node Ω of extreme trans-Neptunian objects (ETNOs) has been attributed to the gravitational effects of an unseen 5-10 Earth-mass planet in the outer solar system. To investigate how selection bias may contribute to this clustering, we consider 14 ETNOs discovered by the Dark Energy Survey, the Outer Solar System Origins Survey, and the survey of Sheppard and Trujillo. Using each survey's published pointing history, depth, and TNO tracking selections, we calculate the joint probability that these objects are consistent with an underlying parent population with uniform distributions in ϖ and Ω. We find that the mean scaled longitude of perihelion and orbital poles of the detected ETNOs are consistent with a uniform population at a level between 17% and 94% and thus conclude that this sample provides no evidence for angular clustering.

Keywords: solar system; planetary science; trans-neptunian objects; kuiper belt; detached objects