adsabs/SciX_UAT_keywords huggingface dataset:
The Third Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars

We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to ≤11 known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with six undetected in radio. Overall, ≥236 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power $\dot{E}$ decreases to its observed minimum near 1033 erg s‑1, approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties, and fit results to guide and be compared with modeling results.

Keywords: binary pulsars; millisecond pulsars; pulsar timing method; rotation powered pulsars; pulsars; gamma-rays; celestial objects catalogs; neutron stars; radio pulsars
On the Energy Dependence of Galactic Cosmic Ray Anisotropies in the Very Local Interstellar Medium

We report on the energy dependence of Galactic cosmic rays (GCRs) in the very local interstellar medium (VLISM) as measured by the Low Energy Charged Particle (LECP) instrument on the Voyager 1 spacecraft. The LECP instrument includes a dual-ended solid-state detector particle telescope mechanically scanning through 360° across eight equally spaced angular sectors. As reported previously, LECP measurements showed a dramatic increase in GCR intensities for all sectors of the ≥211 MeV count rate (CH31) at the Voyager 1 heliopause (HP) crossing in 2012; however, since then the count rate data have demonstrated systematic episodes of intensity decrease for particles around 90° pitch angle. To shed light on the energy dependence of these GCR anisotropies over a wide range of energies, we use Voyager 1 LECP count rate and pulse height analyzer (PHA) data from ≥211 MeV channel together with lower-energy LECP channels. Our analysis shows that, while GCR anisotropies are present over a wide range of energies, there is a decreasing trend in the amplitude of second-order anisotropy with increasing energy during anisotropy episodes. A stronger pitch angle scattering at higher velocities is argued as a potential cause for this energy dependence. A possible cause for this velocity dependence arising from weak rigidity dependence of the scattering mean free path and resulting velocity-dominated scattering rate is discussed. This interpretation is consistent with a recently reported lack of corresponding GCR electron anisotropies.

Keywords: galactic cosmic rays; interstellar medium; heliosphere; heliopause; interstellar magnetic fields; cosmic ray detectors
The Recurrent Nova V745 Sco had a Classical Nova Eruption in 1897 July

Recurrent nova V745 Sco is discovered to have a long-lost nova eruption in 1897 July. Now with four known eruptions (in 1897, 1937, 1989, and 2014), plus two likely missed eruptions (around 1917 and 1963), the average recurrence time is 23 yr, with a fractional rms of 13%.

Keywords: recurrent novae; classical novae; symbiotic novae
Searching for Novel Chemistry in Exoplanetary Atmospheres Using Machine Learning for Anomaly Detection

The next generation of telescopes will yield a substantial increase in the availability of high-quality spectroscopic data for thousands of exoplanets. The sheer volume of data and number of planets to be analyzed greatly motivate the development of new, fast, and efficient methods for flagging interesting planets for reobservation and detailed analysis. We advocate the application of machine learning (ML) techniques for anomaly (novelty) detection to exoplanet transit spectra, with the goal of identifying planets with unusual chemical composition and even searching for unknown biosignatures. We successfully demonstrate the feasibility of two popular anomaly detection methods (local outlier factor and one-class support vector machine) on a large public database of synthetic spectra. We consider several test cases, each with different levels of instrumental noise. In each case, we use receiver operating characteristic curves to quantify and compare the performance of the two ML techniques.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; transmission spectroscopy; clustering; outlier detection; support vector machine
A Dynamically Distinct Stellar Population in the Leading Arm of the Sagittarius Stream

We present a chemical and dynamical analysis of the leading arm (LA) and trailing arm (TA) of the Sagittarius (Sgr) stream, as well as for the Sgr dwarf galaxy core (SC), using red giant branch, main-sequence, and RR Lyrae stars from large spectroscopic survey data. The different chemical properties among the LA, TA, and SC generally agree with recent studies and can be understood by a radial metallicity gradient established in the progenitor of the Sgr dwarf, followed by preferential stellar stripping from the outer part of the Sgr progenitor. One striking finding is a relatively larger fraction of low-eccentricity stars (e < 0.4) in the LA than in the TA and SC. The TA and SC exhibit very similar distributions. Considering that a tidal tail stripped off from a dwarf galaxy maintains the orbital properties of its progenitor, we expect that the e-distribution of the LA should be similar to that of the TA and SC. Thus, the disparate behavior of the e-distribution of the LA is of particular interest. Following the analysis of Vasiliev et al., we attempt to explain the different e-distribution by introducing a time-dependent perturbation of the Milky Way by the Large Magellanic Cloud's (LMC) gravitational pull, resulting in substantial evolution of the angular momentum of the LA stars to produce the low-e stars. In addition, we confirm from RR Lyrae stars with high eccentricity (e > 0.6) that the TA stars farther away from the SC are also affected by disturbances from the LMC.

Keywords: milky way dynamics; sagittarius dwarf spheroidal galaxy; stellar streams; dwarf galaxies; stellar dynamics; stellar abundances
Fear the Shadows of the Giants: On Secular Perturbations in Circumstellar Habitable Zones of Double Stars

After the detection of extrasolar planets in binary- and multiple-star systems, questions arose about their dynamics and habitability. In this study we investigate a five-dimensional parameter space for wide binary stars with a massive planet beyond the habitable zone (HZ). Our aim is to reveal those orbital and physical parameter combinations that expose bodies in the primary star's HZ to secular perturbations. Building on an established semianalytical model, we combine two separate analytical models into a new one to treat the restricted four-body problem. We apply this new Combined Analytical Model (CAM) to different synthetic systems and systematically map the occurrence of secular resonances (SRs). These maps are then visualized as two-dimensional sections of the parameter space. The CAM model has a median error below 3% relative to numerical reference simulations. We also derive a simplified CAM that performs well for hierarchical systems with moderate to large separations between the bodies. Our results show that SRs appear in the HZ even for large secondary-star distances (up to >1000 au) if either (i) the planet's distance is larger than Jupiter's or (ii) its mass is about Saturn's or lower. Changes in the secondary star's eccentricity by stellar flybys or galactic tides can push a formerly dynamically quiet HZ to a high-eccentricity state. Based on these results, we provide the easy-to-use online tool "SHaDoS" that evaluates the CAM for a given user input and traces the locations of SRs in the HZ in two-dimensional parameter space plots.

Keywords: few-body systems; habitable planets; celestial mechanics; exoplanet dynamics; binary stars; apsidal motion
Differential Rotation of the Solar Chromosphere: A Century-long Perspective from Kodaikanal Solar Observatory Ca II K Data

Chromospheric differential rotation is a key component in comprehending the atmospheric coupling between the chromosphere and the photosphere at different phases of the solar cycle. In this study, we therefore utilize the newly calibrated multidecadal Ca II K spectroheliograms (1907-2007) from the Kodaikanal Solar Observatory (KoSO) to investigate the differential rotation of the solar chromosphere using the technique of image cross-correlation. Our analysis yields the chromospheric differential rotation rate Ω(θ) = (14.61 ± 0.04-2.18 ± 0.37 ${\sin }^{2}\theta -1.10\pm 0.61{\sin }^{4}\theta )^\circ $ day-1. These results suggest the chromospheric plages exhibit an equatorial rotation rate 1.59% faster than the photosphere when compared with the differential rotation rate measured using sunspots and also a smaller latitudinal gradient compared to the same. To compare our results to those from other observatories, we have applied our method on a small sample of Ca II K data from Rome, Meudon, and Mount Wilson observatories, which support our findings from KoSO data. Additionally, we have not found any significant north-south asymmetry or any systematic variation in chromospheric differential rotation over the last century.

Keywords: solar cycle; plages; solar chromosphere; solar rotation; solar differential rotation
Discovery of a Universal Correlation for Long and Short GRBs and Its Application for the Study of Luminosity Function and Formation Rate

Gamma-ray bursts (GRBs) are known to be the most violent explosions in the universe, and a variety of correlations between observable GRB properties have been proposed in the literature, but none of these correlations are valid for both long and short GRBs. In this paper we report the discovery of a universal correlation that is suitable for both long and short GRBs using three prompt emission properties of GRBs, I.e., the isotropic peak luminosity Liso, the peak energy of the time-integrated prompt emission spectrum Epeak, and the "high signal" timescale T0.45, ${L}_{\mathrm{iso}}\propto {E}_{\mathrm{peak}}^{1.94}{T}_{0.45}^{0.37}$ . This universal correlation involves properties of GRB prompt emission and does not require knowledge of the afterglow phase, which can be used as a relatively unbiased redshift estimator. Here we use this correlation to estimate the pseudoredshifts for short GRBs and then use the Lynden-Bell method to obtain a nonparametric estimate of their luminosity function and formation rate. The luminosity function is $\psi ({L}_{0})\propto {L}_{0}^{-0.63\pm 0.07}$ for dim SGRBs and $\psi ({L}_{0})\propto {L}_{0}^{-1.96\pm 0.28}$ for bright SGRBs, with the break point ${6.95}_{-0.76}^{+0.84}\times {10}^{50}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ . The local formation rate of SGRBs is about 15 events Gpc-3 yr-1 . This universal correlation may have important implications for GRB physics, implying that the long and short GRBs should share similar radiation processes.

Keywords: gamma-ray bursts; burst astrophysics; cosmological parameters; cosmology
Quenching and the UVJ Diagram in the SIMBA Cosmological Simulation

Over the past decade, rest-frame color-color diagrams have become popular tools for selecting quiescent galaxies at high redshift, breaking the color degeneracy between quiescent and dust-reddened star-forming galaxies. In this work, we study one such color-color selection tool-the rest-frame U - V versus V - J diagram-by employing mock observations of cosmological galaxy formation simulations. In particular, we conduct numerical experiments assessing both trends in galaxy properties in UVJ space and the color-color evolution of massive galaxies as they quench at redshifts z ~ 1-2. We find that our models broadly reproduce the observed UVJ diagram at z = 1-2, including (for the first time in a cosmological simulation) reproducing the population of extremely dust-reddened galaxies in the top right of the UVJ diagram. However, our models primarily populate this region with low-mass galaxies and do not produce as clear a bimodality between star-forming and quiescent galaxies as is seen in observations. The former issue is due to an excess of dust in low-mass galaxies and relatively gray attenuation curves in high-mass galaxies, while the latter is due to the overpopulation of the green valley in SIMBA. When investigating the time evolution of galaxies on the UVJ diagram, we find that the quenching pathway on the UVJ diagram is independent of the quenching timescale, and instead dependent primarily on the average specific star formation rate in the 1 Gyr prior to the onset of quenching. Our results support the interpretation of different quenching pathways as corresponding to the divergent evolution of post-starburst and green valley galaxies.

Keywords: two-color diagrams; galaxy quenching; post-starburst galaxies
Why Radio Quiet Quasars are Preferred over Radio Loud Quasars Regardless of Environment and Redshift

Evidence has accumulated suggesting the clustering of radio loud quasars (RLQs) is greater than for radio quiet quasars. We interpret these results in a context in which the fraction of RLQ formation is fRLQ ≤ fRQQ compared to that for radio quiet quasars for all environments and redshifts. Because we assume that post-merger cold gas onto large black holes produces either a radio loud or a radio quiet quasar, we show that for the largest black hole masses that live in the largest dark matter halos, fRLQ approaches 0.5 from below but does not exceed it, such that in rich clusters the formation of an RLQ tends to be equally likely to occur as a radio quiet quasar. In dark matter halos with smaller mass, by contrast, radio quiet quasars are more likely to form and the likelihood increases inversely with dark matter halo mass. As a result, averaging over a population of radio loud and radio quiet quasars will necessarily generate lower average black hole masses for the radio quiet subgroup. Hence, despite the fact that the formation of radio quiet quasars is preferred over RLQs in any environment, at any mass scale, at any luminosity, or redshift, averaging over a range of RLQs will give the appearance that they are preferred in cluster environments over radio quiet quasars. We show how this also accounts for the order of magnitude difference in the total number of jetted active galaxies compared to nonjetted counterparts.

Keywords: radio loud quasars; radio quiet quasars
Molecules with ALMA at Planet-forming Scales (MAPS). II. CLEAN Strategies for Synthesizing Images of Molecular Line Emission in Protoplanetary Disks

The Molecules with ALMA at Planet-forming Scales Large Program (MAPS LP) surveyed the chemical structures of five protoplanetary disks across more than 40 different spectral lines at high angular resolution (0"15 and 0"30 beams for Bands 6 and 3, respectively) and sensitivity (spanning 0.3-1.3 mJy beam-1 and 0.4-1.9 mJy beam-1 for Bands 6 and 3, respectively). In this article, we describe the multistage workflow-built around the CASA tclean image deconvolution procedure-that we used to generate the core data product of the MAPS LP: the position-position-velocity image cubes for each spectral line. Owing to the expansive nature of the survey, we encountered a range of imaging challenges: some are familiar to the submillimeter protoplanetary disk community, like the need to use an accurate CLEAN mask, and others are less well known, like the incorrect default flux scaling of the CLEAN residual map first described by Jorsater & van Moorsel (the "JvM effect"). We distill lessons learned into recommended workflows for synthesizing image cubes of molecular emission. In particular, we describe how to produce image cubes with accurate fluxes via "JvM correction," a procedure that is generally applicable to any image synthesized via CLEAN deconvolution but is especially critical for low signal-to-noise ratio (S/N) emission. We further explain how we used visibility tapering to promote a common, fiducial beam size and contextualize the interpretation of S/N when detecting molecular emission from protoplanetary disks. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: protoplanetary disks; submillimeter astronomy; radio interferometry; deconvolution
Variability Census of Legacy Catalogs. I. 1800+ New δ Scuti and γ Doradus Stars

Discovery of 1200+ new δ Scuti and 680+ new γ Doradus stars is presented as the preliminary results of a variability vetting census of the four legacy catalogs: BD, HD, SAO and PPM. This systematic screening of cataloged stars is part of a special survey project that aims to identify bright variable stars based on publicly accessible high-precision space photometry. Identification was performed using a Python program that involved human intervention and visual inspection. Successive results will be reported separately in a dynamic online catalog as the census progresses. *Dedicated to my wife Jingyun Zhang.

Keywords: pulsating variable stars; delta scuti variable stars; gamma doradus variable stars
Near-infrared Spectroscopy of CK Vulpeculae: Revealing a Remarkably Powerful Blast from the Past

CK Vulpeculae (CK Vul), which erupted in AD 1670-71, was long considered to be a nova outburst; however, recent observations have required that alternative scenarios be considered. Long-slit infrared spectroscopy of a forbidden line of iron reported here has revealed high line-of-sight velocities (∼±900 km s-1) of the ansae at the tips of the bipolar lobes imaged in Hα in 2010. The deprojected velocities of the tips are approximately ±2130 km s-1 assuming the previously derived inclination angle of 65° for the axis of cylindrical symmetry of the bipolar nebula. Such high velocities are in stark contrast to previous reports of much lower expansion velocities in CK Vul. Based on the deprojected velocities of the tips and their angular expansion measured over a 10 yr baseline, we derive a revised estimate, with estimated uncertainties, of ${3.2}_{-0.6}^{+0.9}$ kpc for the distance to CK Vul. This implies that the absolute visual magnitude at the peak of the 1670 explosion was ${M}_{V}=-{12.4}_{-2.4}^{+1.3}$ , indicating that the 1670 event was far more luminous than previous estimates and brighter than any classical nova or any Galactic stellar merger. We propose that CK Vul belongs to the class of intermediate-luminosity optical transients (ILOTs), objects which bridge the luminosity gap between novae and supernovae. While eruptions in lower luminosity ILOTs are attributed to merger events, the origin of the highly luminous ILOT outbursts is currently not known.

Keywords: stellar phenomena; stellar winds; stellar mass loss; stellar luminosities; infrared sources
The Relative Contribution to Heavy Metals Production from Binary Neutron Star Mergers and Neutron Star-Black Hole Mergers

The origin of the heavy elements in the universe is not fully determined. Neutron star-black hole (NSBH) and binary neutron star (BNS) mergers may both produce heavy elements via rapid neutron-capture (r-process). We use the recent detection of gravitational waves from NSBHs, improved measurements of the neutron star equation of state (EoS), and the most modern numerical simulations of ejected material from binary collisions to measure the relative contribution of NSBHs and BNSs to the production of heavy elements. As the amount of r-process ejecta depends on the mass and spin distribution of the compact objects, as well as on the EoS of the neutron stars, we consider various models for these quantities, informed by gravitational-wave and pulsar data. We find that in most scenarios, BNSs have produced more r-process elements than NSBHs over the past 2.5 billion years. If black holes have preferentially small spins, BNSs can produce at least twice the amount of r-process elements than NSBHs. If black hole spins are small and there is a dearth of low-mass (<5M⊙) black holes within NSBH binaries, BNSs can account for the near totality of the r-process elements from binaries. For NSBH to produce a large fraction of r-process elements, black holes in NSBHs must have small masses and large aligned spins, which is disfavored by current data.

Keywords: gravitational wave astronomy; gravitational waves; heavy metal stars
Toward 3D Retrieval of Exoplanet Atmospheres: Assessing Thermochemical Equilibrium Estimation Methods

Characterizing exoplanetary atmospheres via Bayesian retrievals requires assuming some chemistry model, such as thermochemical equilibrium or parameterized abundances. The higher-resolution data offered by upcoming telescopes enable more complex chemistry models within retrieval frameworks. Yet many chemistry codes that model more complex processes like photochemistry and vertical transport are computationally expensive, and directly incorporating them into a 1D retrieval model can result in prohibitively long execution times. Additionally, phase-curve observations with upcoming telescopes motivate 2D and 3D retrieval models, further exacerbating the lengthy runtime for retrieval frameworks with complex chemistry models. Here we compare thermochemical equilibrium approximation methods based on their speed and accuracy with respect to a Gibbs energy-minimization code. We find that, while all methods offer orders-of-magnitude reductions in computational cost, neural network surrogate models perform more accurately than the other approaches considered, achieving a median absolute dex error of <0.03 for the phase space considered. While our results are based on a 1D chemistry model, our study suggests that higher-dimensional chemistry models could be incorporated into retrieval models via this surrogate modeling approach.

Keywords: exoplanet atmospheric composition; exoplanet atmospheres; neural networks; regression; chemical abundances
Robust 1-norm Periodograms for Analysis of Noisy Non-Gaussian Time Series with Irregular Cadences: Application to VLBI Astrometry of Quasars

Astronomical time series often have non-uniform sampling in time, or irregular cadences, with long gaps separating clusters of observations. Some of these data sets are also explicitly non-Gaussian with respect to the expected model fit, or the simple mean. The standard Lomb–Scargle periodogram is based on the least squares solution for a set of test periods and, therefore, is easily corrupted by a subset of statistical outliers or an intrinsically non-Gaussian population. It can produce completely misleading results for heavy-tailed distribution of residuals. We propose a robust 1-norm periodogram technique, which is based on the principles of robust statistical estimation. This technique can be implemented in weighted or unweighted options. The method is described in detail and compared with the classical least squares periodogram on a set of astrometric VLBI measurements of the ICRF quasar IERS B0642+449. It is uniformly applied to a collection of 259 ICRF3 quasars each with more than 200 epoch VLBI measurements, resulting in a list of 49 objects with quasi-periodic position changes above the 3σ level, which warrant further investigation.

Keywords: astrometry; lomb-scargle periodogram; astronomy data analysis; algorithms; quasars; very long baseline interferometry; period search