adsabs/SciX_UAT_keywords huggingface dataset:
Discovery of Four Pulsars in a Pilot Survey at Intermediate Galactic Latitudes with FAST

We present the discovery and timing results of four pulsars discovered in a pilot survey at intermediate Galactic latitudes with the Five-hundred Aperture Spherical Telescope (FAST). Among these pulsars, two belong to the category of millisecond pulsars (MSPs) with spin periods of less than 20 ms. The other two fall under the classification of "mildly recycled" pulsars, with massive white dwarfs as companions. Remarkably, this small survey, covering an area of 4.7 deg2, led to the discovery of four recycled pulsars. Such success underscores the immense potential of future surveys at intermediate Galactic latitudes. In order to assess the potential yield of MSPs, we conducted population simulations and found that both FAST and Parkes new phased array feed surveys, focusing on intermediate Galactic latitudes, have the capacity to uncover several hundred new MSPs.

Keywords: radio pulsars
Extinction along Sightlines Sampled by the APO Catalog of DIBs

Identification of molecular carriers for diffuse interstellar bands (DIBs) may stem in part from the determination of interrelated lines using the Apache Point Observatory Catalog of DIBs. However, Pearson correlations may be impacted by the number of interstellar clouds along the sightlines. The trend of extinction with distance was constrained using Bayestar19 and Gaia DR3, and clouds were identified via step-functions and extended increasing linear progressions may be indicative of traversal through dense spiral arms. Thirteen sightlines are likely observed through more than one cloud. The hypergiants HD168625 and VI Cyg 12 are contaminated by local nebulosity and circumstellar disks. New findings presented here support the reddenings cited within the Apache Point Observatory catalog of DIBs.

Keywords: diffuse interstellar bands
Bottom's Dream and the Amplification of Filamentary Gas Structures and Stellar Spiral Arms

Theories of spiral structure traditionally separate into tight-winding Lin–Shu spiral density waves and the swing-amplified material patterns of Goldreich & Lynden-Bell and Julian & Toomre. In this paper we consolidate these two types of spirals into a unified description, treating density waves beyond the tight-winding limit, in the regime of shearing and nonsteady open spirals. This shearing wave scenario novelly captures swing amplification that enables structure formation above conventional Q thresholds. However, it also highlights the fundamental role of spiral forcing on the amplification process in general, whether the wave is shearing or not. Thus it captures resonant and nonresonant mode growth through the donkey effect described by Lynden-Bell & Kalnajs and, critically, the cessation of growth when donkey behavior is no longer permitted. Our calculations predict growth exclusive to trailing spirals above the Jeans length, the prominence of spirals across a range of orientations that increases with decreasing arm multiplicity, and a critical orientation where growth is fastest that is the same for both modes and material patterns. Predicted structures are consistent with highly regular, high-multiplicity gaseous spur features and long filaments spaced close to the Jeans scale in spirals and bars. Applied to stellar disks, conditions favor low multiplicity (m < 5) open trailing spirals with pitch angles in the observed range 10° < i p < 50°. The results of this work serve as a basis for describing spirals as a unified class of transient waves, abundantly stimulated but narrowly selected for growth depending on local conditions.

Keywords: spiral arms; spiral galaxies; spiral pitch angle; interstellar medium; galaxy dynamics
Quasi-periodic Particle Acceleration in a Solar Flare

A common feature of electromagnetic emission from solar flares is the presence of intensity pulsations that vary as a function of time. Known as quasi-periodic pulsations (QPPs), these variations in flux appear to include periodic components and characteristic timescales. Here, we analyze a GOES M3.7 class flare exhibiting pronounced QPPs across a broad band of wavelengths using imaging and time series analysis. We identify QPPs in the time series of X-ray, low-frequency radio, and extreme ultraviolet (EUV) wavelengths using wavelet analysis, and localize the region of the flare site from which the QPPs originate via X-ray and EUV imaging. It was found that the pulsations within the 171 Å, 1600 Å, soft X-ray, and hard X-ray light curves yielded similar periods of ${122}_{-22}^{+26}$ <!-- --> s, ${131}_{-27}^{+36}$ <!-- --> s, ${123}_{-26}^{+11}$ <!-- --> s, and ${137}_{-56}^{+49}$ <!-- --> s, respectively, indicating a common progenitor. The low-frequency radio emission at 2.5 MHz contained a longer period of ∼231 s. Imaging analysis indicates that the location of the X-ray and EUV pulsations originates from a hard X-ray footpoint linked to a system of nearby open magnetic field lines. Our results suggest that intermittent particle acceleration, likely due to "bursty" magnetic reconnection, is responsible for the QPPs. The precipitating electrons accelerated toward the chromosphere produce the X-ray and EUV pulsations, while the escaping electrons result in low-frequency radio pulses in the form of type III radio bursts. The modulation of the reconnection process, resulting in episodic particle acceleration, explains the presence of these QPPs across the entire spatial range of flaring emission.

Keywords: solar flares; solar activity; solar radio flares; solar x-ray flares; solar extreme ultraviolet emission; solar oscillations
Spectroscopic r-Process Abundance Retrieval for Kilonovae. I. The Inferred Abundance Pattern of Early Emission from GW170817

Freshly synthesized r-process elements in kilonovae ejecta imprint absorption features on optical spectra, as observed in the GW170817 binary neutron star merger. These spectral features encode insights into the physical conditions of the r-process and the origins of the ejected material, but associating features with particular elements and inferring the resultant abundance pattern is computationally challenging. We introduce Spectroscopic r-Process Abundance Retrieval for Kilonovae (SPARK), a modular framework to perform Bayesian inference on kilonova spectra with the goals of inferring elemental abundance patterns and identifying absorption features at early times. SPARK inputs an atomic line list and abundance patterns from reaction network calculations into the TARDIS radiative transfer code. It then performs fast Bayesian inference on observed kilonova spectra by training a Gaussian process surrogate for the approximate posteriors of kilonova ejecta parameters, via active learning. We use the spectrum of GW170817 at 1.4 days to perform the first inference on a kilonova spectrum, and recover a complete abundance pattern. Our inference shows that this ejecta was generated by an r-process with either (1) high electron fraction Y e ~ 0.35 and high entropy s/k B ~ 25, or, (2) a more moderate Y e ~ 0.30 and s/k B ~ 14. These parameters are consistent with a shocked, polar dynamical component, and a viscously driven outflow from a remnant accretion disk, respectively. We also recover previous identifications of strontium absorption at ~8000 Å, and tentatively identify yttrium and/or zirconium at ≲4500 Å. Our approach will enable computationally tractable inference on the spectra of future kilonovae discovered through multimessenger observations.

Keywords: nuclear abundances; r-process; radiative transfer simulations; spectral line identification
A Serendipitous Discovery of GeV Gamma-Ray Emission from Supernova 2004dj in a Survey of Nearby Star-forming Galaxies with Fermi-LAT

The interaction between a supernova ejecta and the circumstellar medium drives a strong shock wave that accelerates particles (I.e., electrons and protons). The radio and X-ray emission observed after the supernova explosion can be interpreted as synchrotron emission from accelerated electrons. The accelerated protons are expected to produce GeV-TeV gamma-ray emission via proton-proton collisions, but the flux is usually low since only a small fraction of the supernova kinetic energy is converted into the shock energy at the very early time. The low gamma-ray flux of the nearest supernova explosion, SN 1987A, agrees with this picture. Here we report a serendipitous discovery of a fading GeV gamma-ray source in spatial coincidence with one of the nearest and brightest supernova—SN 2004dj from our gamma-ray survey of nearby star-forming galaxies with Fermi-LAT. The total gamma-ray energy released by SN 2004dj is about 6 × 1047 erg. We interpret this gamma-ray emission arising from the supernova ejecta interacting with a surrounding high-density shell, which decelerates the ejecta and converts ∼1% of the SN kinetic energy to relativistic protons.

Keywords: gamma-ray sources; type ii supernovae; non-thermal radiation sources
A Possible Enrichment of Heavy and Ultraheavy Ions in Solar Energetic Particle Events Due to a Combined Effect of Stochastic Acceleration and Coulomb Losses

Solar particle events that are rich in 3He typically also exhibit large overabundances of heavy and ultraheavy ions that increase with the mass of the ions. To explain these observations we apply our charge-consistent acceleration model, which takes into account the acceleration efficiency as a function of the charge to mass ratio of the ion, as well as the charge-dependent Coulomb energy losses, to consider the acceleration of ions within a wide range of their nuclear charge. Because the considerations of particle acceleration were restricted so far by tabulated values of ionization and recombination coefficients that were available only for a limited set of ions, we make use of our method developed earlier and calculate the rates of ions resembling the three representative mass groups of ultraheavy ions. We demonstrate that smaller Coulomb losses together with higher acceleration efficiency result in the enhancements of heavy and ultraheavy ions, in accordance with recent observations. We also conclude that the existing measurements of ultraheavy ions in impulsive solar energetic particle events provide evidence in favor of a magnetic turbulence in the acceleration region with spectral index S ≥ 2.

Keywords: solar energetic particles; solar particle emission; solar flares
The Odd Dark Matter Halos of Isolated Gas-rich Ultradiffuse Galaxies

We analyze circular velocity profiles of seven ultradiffuse galaxies (UDGs) that are isolated and gas-rich. Assuming that the dark matter halos of these UDGs have a Navarro-Frenk-White (NFW) density profile or a Read density profile (which allows for constant-density cores), the inferred halo concentrations are systematically lower than the cosmological median, even as low as -0.6 dex (about 5σ away) in some cases. Alternatively, similar fits can be obtained with a density profile that scales roughly as 1/r 2 for radii larger than a few kiloparsecs. Both solutions require the radius where the halo circular velocity peaks ( ${R}_{\max }$ ) to be much larger than the median expectation. Surprisingly, we find an overabundance of such large- ${R}_{\max }$ halos in the IllustrisTNG dark-matter-only simulations compared to the Gaussian expectation. These halos form late and have higher spins compared to median halos of similar masses. The inner densities of the most extreme among these late-forming halos are higher than their NFW counterparts, leading to a ~1/r 2 density profile. However, the two well-resolved UDGs in our sample strongly prefer lower dark matter densities in the center than the simulated ones. Comparing to IllustrisTNG hydrodynamical simulations, we also find a tension in getting both low enough circular velocities and high enough halo mass to accommodate the measurements. Our results indicate that the gas-rich UDGs present a significant challenge for galaxy formation models.

Keywords: low surface brightness galaxies; dark matter
CARAMEL-GAS: A Step toward Fast Empirical Models of the Broad-line-emitting Gas

Fast empirical models of the broad emission line region (BLR) are a powerful tool to interpret velocity-resolved reverberation mapping (RM) data, estimate the mass of the supermassive black holes, and gain insight into its geometry and kinematics. Much of the effort so far has been devoted to describing the emissivity of one emission line at a time. We present here an alternative approach aimed at describing the underlying BLR gas distribution, by exploiting simple numerical recipes to connect it with emissivity. This approach is a step toward describing multiple emission lines originating from the same gas and allows us to clarify some issues related to the interpretation of RM data. We illustrate this approach-implemented in the code CARAMEL-GAS-using three data sets covering the Hβ emission line (Mrk 50, Mrk 1511, Arp 151) that have been modeled using the emissivity-based version of the code. As expected, we find differences in the parameters describing the BLR gas and emissivity distribution, but the emissivity-weighted lag measurements and all other model parameters including black hole mass and overall BLR morphology and kinematics are consistent with the previous measurements. We also model the Hα emission line for Arp 151 using both the gas- and emissivity-based BLR models. We find ionization stratification in the BLR with Hα arising at larger radii than Hβ, while all other model parameters are consistent within the uncertainties.

Keywords: supermassive black holes; astronomy data modeling; photoionization; reverberation mapping
Detection of an Atmospheric Outflow from the Young Hot Saturn TOI-1268b

Photoevaporative mass-loss rates are expected to be highest when planets are young and the host star is more active, but to date there have been relatively few measurements of mass-loss rates for young gas giant exoplanets. In this study we measure the present-day atmospheric mass-loss rate of TOI-1268b, a young (110–380 Myr) and low density (0.71 ${}_{-0.13}^{+0.17}$ g cm‑3) hot Saturn located near the upper edge of the Neptune desert. We use Palomar/WIRC to search for excess absorption in the 1083 nm helium triplet during two transits of TOI-1268b. We find that it has a larger transit depth ( ${0.285}_{-0.050}^{+0.048} \% $ excess) in the helium bandpass than in the TESS observations, and convert this excess absorption into a mass-loss rate by modeling the outflow as a Parker wind. Our results indicate that this planet is losing mass at a rate of $\mathrm{log}\dot{M}=10.2\pm 0.3$ g s‑1 and has a thermosphere temperature of ${6900}_{-1200}^{+1800}$ K. This corresponds to a predicted atmospheric lifetime much larger than 10 Gyr. Our result suggests that photoevaporation is weak in gas giant exoplanets even at early ages.

Keywords: exoplanet atmospheres; narrow band photometry
The HERBAL Model: A Hierarchical Errors-in-variables Bayesian Lognormal Hurdle Model for Galactic Globular Cluster Populations

Galaxy stellar mass is known to be monotonically related to the size of the galaxy's globular cluster (GC) population for Milky Way sized and larger galaxies. However, the relation becomes ambiguous for dwarf galaxies, where there is some evidence for a downturn in GC population size at low galaxy masses. Smaller dwarfs are increasingly likely to have no GCs, and these zeros cannot be easily incorporated into linear models. We introduce the Hierarchical Errors-in-variables ERrors-in-variables BAyesian Lognormal hurdle (HERBAL) model to represent the relationship between dwarf galaxies and their GC populations, and apply it to the sample of Local Group galaxies, where the luminosity range coverage is maximal. This bimodal model accurately represents the two populations of dwarf galaxies: those that have GCs and those that do not. Our model thoroughly accounts for all uncertainties, including measurement uncertainty, uncertainty in luminosity to stellar mass conversions, and intrinsic scatter. The hierarchical nature of our Bayesian model also allows us to estimate galaxy masses and individual mass-to-light ratios from luminosity data within the model. We find that 50% of galaxies are expected to host GC populations at a stellar mass of ${\mathrm{log}}_{10}({M}_{* })=6.996$ , and that the expected mass of GC populations remains linear down to the smallest galaxies. Our hierarchical model recovers an accurate estimate of the Milky Way stellar mass. Under our assumed error model, we find a nonzero intrinsic scatter of ${0.59}_{-0.21}^{+0.3}$ (95% credible interval) that should be accounted for in future models.

Keywords: astrostatistics; interdisciplinary astronomy; bayesian statistics; hierarchical models; globular star clusters; local group; galaxies; galactic and extragalactic astronomy; dwarf galaxies
A Panchromatic Study of the X-Ray Binary Population in NGC 300 on Subgalactic Scales

The population-wide properties and demographics of extragalactic X-ray binaries (XRBs) correlate with the star formation rates (SFRs), stellar masses (M ⋆), and environmental factors (such as metallicity, Z) of their host galaxy. Although there is evidence that XRB scaling relations (L X/SFR for high-mass XRBs (HMXBs) and L X/M ⋆ for low-mass XRBs) may depend on metallicity and stellar age across large samples of XRB-hosting galaxies, disentangling the effects of metallicity and stellar age from stochastic effects, particularly on subgalactic scales, remains a challenge. We use archival X-ray through IR observations of the nearby galaxy NGC 300 to self-consistently model the broadband spectral energy distribution and examine radial trends in its XRB population. We measure a current (<100 Myr) SFR of 0.18 ± 0.08 M⊙ yr‑1 and stellar mass M ⋆ = M⊙. Although we measure a metallicity gradient and radially resolved star formation histories that are consistent with the literature, there is a clear excess in the number of X-ray sources below ∼1037 erg s‑1 that are likely a mix of variable XRBs and additional background active galactic nuclei. When we compare the subgalactic L X/SFR ratios as a function of Z to the galaxy-integrated L X-SFR-Z relationships from the literature, we find that only the regions hosting the youngest (≲30 Myr) HMXBs agree with predictions, hinting at time evolution of the L X–SFR–Z relationship.

Keywords: x-ray binary stars; high mass x-ray binary stars; compact objects; spiral galaxies
Variability and Spectral Behavior of Gamma-Ray Flares of 3C 279

3C 279 showed enhanced flux variations in Fermi-LAT γ-ray observations from 2018 January to June. We present a detailed Fermi-LAT analysis to investigate the variability and spectral behaviors of 3C 279 during the γ-ray flares in 2018. In this work, we analyzed the γ-ray spectra and found that the spectra in either the flaring or quiescent states do not show any clear breaks (or cutoffs). This indicates that the dissipation region is outside the broad-line region, and the energy dissipation may be due to the inverse Compton process of scattering the dust torus infrared photons, this result is also consistent with that in Tolamatti et al. An external inverse Compton scattering of dusty torus (DT) photons is employed to calculate the broadband spectral energy distribution (SED). This model was further supported by the fact that we found flare decay timescale was consistent with the cooling time of relativistic electrons through DT photons. During the SED modeling, a relatively harder spectrum for the electron energy distribution is found and suggests these electrons may not be accelerated by the shock that happened in the dissipation region. Besides, the magnetic reconnection is also ruled out due to a low magnetization ratio. Thus, we suggest an injection of higher-energy electrons from outside the blob and raising the flare.

Keywords: active galaxies; gamma-rays; galaxy jets; quasars
Generative Models of Multichannel Data from a Single Example-Application to Dust Emission

The quest for primordial B-modes in the cosmic microwave background has emphasized the need for refined models of the Galactic dust foreground. Here we aim at building a realistic statistical model of the multifrequency dust emission from a single example. We introduce a generic methodology relying on microcanonical gradient descent models conditioned by an extended family of wavelet phase harmonic (WPH) statistics. To tackle the multichannel aspect of the data, we define cross-WPH statistics, quantifying non-Gaussian correlations between maps. Our data-driven methodology could apply to various contexts, and we have updated the software PyWPH, on which this work relies, accordingly. Applying this to dust emission maps built from a magnetohydrodynamics simulation, we construct and assess two generative models: (1) a (I, E, B) multi-observable input, and (2) a ${\{{I}_{\nu }\}}_{\nu }$ multifrequency input. The samples exhibit consistent features compared to the original maps. A statistical analysis of model 1 shows that the power spectra, distributions of pixels, and Minkowski functionals are captured to a good extent. We analyze model 2 by fitting the spectral energy distribution (SED) of both the synthetic and original maps with a modified blackbody (MBB) law. The maps are equally well fitted, and a comparison of the MBB parameters shows that our model succeeds in capturing the spatial variations of the SED from the data. Besides the perspectives of this work for dust emission modeling, the introduction of cross-WPH statistics opens a new avenue to characterize non-Gaussian interactions across different maps, which we believe will be fruitful for astrophysics.

Keywords: astrostatistics; interstellar dust; cosmic microwave background radiation
Accelerated Growth of Seed Black Holes by Dust in the Early Universe

We explore the effect of dust on the growth of seed black holes (BHs) in the early universe. Previous 1D radiation-hydrodynamic (RHD) simulations show that increased radiation pressure on dust further suppresses the accretion rate than the case for the chemically pristine gas. Using the Enzo+Moray code, we perform a suite of 3D RHD simulations of accreting BHs in a dusty interstellar medium (ISM). We use the modified Grackle cooling library to consider dust physics in its nonequilibrium chemistry. The BH goes through an early evolutionary phase, where ionizing BH radiation creates an oscillating H II region as it cycles between accretion and feedback. As the simulations proceed, dense cold gas accumulates outside the ionized region where inflow from the neutral medium meets the outflow driven by radiation pressure. In the late phase, high-density gas streams develop and break the quasi-spherical symmetry of the ionized region, rapidly boosting the accretion rate. The late phase is characterized by the coexistence of strong ionized outflows and fueling high-density gas inflows. The mean accretion rate increases with metallicity reaching a peak at Z ~ 0.01-0.1 Z ☉, one order of magnitude higher than the one for pristine gas. However, as the metallicity approaches the solar abundance, the mean accretion rate drops as the radiation pressure becomes strong enough to drive out the high-density gas. Our results indicate that a dusty metal-poor ISM can accelerate the growth rate of BHs in the early universe, but can also stun its growth as the ISM is further enriched toward the solar abundance.

Keywords: accretion; black hole physics; hydrodynamics; intermediate-mass black holes; interstellar dust; radiative transfer simulations