Sazuna/UAT_keywords huggingface dataset:
The NANOGrav 15 yr Dataset: Search for Gravitational Scattering of Pulsars by Free-floating Objects in Interstellar Space. Free-floating objects (FFOs) in interstellar space—rogue planets, brown dwarfs, and large asteroids that are not gravitationally bound to any star—are expected to be ubiquitous throughout the Milky Way. Recent microlensing surveys have discovered several free-floating planets that are not bound to any known stellar systems. Additionally, three interstellar objects, namely 1I/'Oumuamua, 2I/Borisov, and 3I/ATLAS, have been detected passing through our solar system on hyperbolic trajectories. In this work, we search for FFOs on hyperbolic orbits that pass near millisecond pulsars (MSPs), where their gravitational influence can induce detectable perturbations in pulse arrival times. Using the NANOGrav 15 yr narrow band dataset, which contains high-precision timing data for 68 MSPs, we conduct a search for such hyperbolic scattering events between FFOs and pulsars. Although no statistically significant events were detected, this nondetection enables us to place upper limits (ULs) on the number density of FFOs as a function of their mass within our local region of the Galaxy. For example, the UL on the number density for Jupiter-mass FFOs (∼10−2.5─10−3.5 M⊙) obtained from different pulsars ranges from 5.25 × 106 pc−3 to 5.37 × 109 pc−3, while the UL calculated by combining results from all the pulsars is 6.03 × 105 pc−3. These results represent the first constraints on FFO population derived from pulsar timing data.

Keywords: Brown dwarfs, Millisecond pulsars, Free floating planets, Interstellar objects, Primordial black holes
TRAO Survey of the Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO-FUNS). IV. Filaments and Dense Cores in the W40 and Serpens South Regions of Aquila. We present the results of molecular line observations toward the W40 and Serpens South regions of the Aquila molecular cloud complex, conducted as part of the Taeduk Radio Astronomy Observatory survey of Filaments, the Universal Nursery of Stars project to investigate the role of filamentary structures in the formation of dense cores and stars in molecular clouds. We performed a Gaussian decomposition of the C18O spectra to disentangle multiple velocity components along the line of sight and a "Friends-of-Friends" algorithm on these decomposed components to identify 24 velocity-coherent filaments in the observed region. The "FellWalker" algorithm is applied on the N2H+ integrated intensity map to identify the dense cores embedded within the filaments. Many of the filaments previously identified from the Herschel survey are found to contain multiple velocity-coherent filaments. Virial analysis indicated that all of our identified filaments are thermally supercritical and gravitationally bound. Velocity gradients are observed along the filaments in the vicinity of embedded dense cores, indicating the presence of longitudinal flows that contribute to core formation. The median mass flow rate across the observed region is estimated to be ∼35 M⊙ Myr−1, with Serpens South showing a rate ∼40% higher than W40. The analysis of nonthermal motions revealed that the dense cores mainly show subsonic to transonic motions, while their host filaments are mostly supersonic, suggesting that the turbulent motions in filaments may dissipate on smaller scales, allowing core formation. These findings highlight the essential role of the filaments' criticality, mass flow, and turbulent dissipation in the formation of dense cores within the filaments.

Keywords: Interstellar filaments, Molecular clouds, Star formation, Interstellar medium, Radio astronomy
ExoJAX Retrievals of VLT/CRIRES Spectra of Luhman 16AB: C/O Ratios and Systematic Uncertainties. We present atmospheric retrievals of the benchmark brown dwarf binary Luhman 16AB using high-resolution VLT/CRIRES spectra and the differentiable framework ExoJAX. We derive elemental abundances and temperature─pressure (T─P) profiles while explicitly testing the robustness of the results against major sources of systematic uncertainty. We first perform retrievals with a power-law T─P profile and assess the sensitivity of inferred molecular abundances and C/O ratios to different CO line lists (ExoMol, HITEMP with air- and H2-broadening). We then introduce a flexible Gaussian process-based T─P profile, allowing a nonparametric characterization of the thermal structure and a more conservative treatment of uncertainties. For both components, we infer C/O ratios of about 0.67, slightly above solar, with line list systematics at the 7% level emerging as the dominant source of uncertainty, whereas assumptions about T─P parameterization or photometric variability play a lesser role. The retrieved T─P profiles and molecular abundances are broadly consistent with atmospheric models and equilibrium chemistry. Our results establish Luhman 16AB as a key anchor for substellar C/O measurements, demonstrate the utility of flexible T─P modeling in high-resolution retrievals, and highlight the importance of systematic tests—particularly line list uncertainties—for robust comparisons between brown dwarfs and giant exoplanets.

Keywords: High resolution spectroscopy, Brown dwarfs, Molecular spectroscopy, Exoplanet atmospheres, T dwarfs
SMSS J022423.27−573705.1: An Extremely Metal-poor Star with the Most Pronounced Weak r-process Signature. We present the measurement of 26 elemental abundances of SMSS J022423.27−573705.1 (SMSS 0224─5737), an extremely metal-poor (EMP) star with a weak r-process signature. We report the measurements of N, O, V, Zn, and Ba, and the upper limits for Mo, Ru, Pd, Ag, and Eu for the first time. SMSS 0224─5737 exhibits low C abundance and high N and O abundances, suggesting that C is converted to N by the enhanced mixing during the evolution. The abundance pattern up to the Fe-peak elements is generally in good agreement with the average abundance of EMP stars, although a notable feature is the high [Zn/Fe] ratio ([Zn/Fe] = + 0.88). We confirm the enhancement of the first-peak neutron-capture elements (Sr, Y, and Zr) and determine a low Ba abundance [Ba/H] = −5.25, that is, [Ba/Fe] = −1.45. The extremely high ratio of [Zr/Ba] = +2.60 makes SMSS 0224─5737 the EMP star with the most pronounced weak r-process signature observed to date. The abundance pattern of the neutron-capture elements is compared with the yields from r-process nucleosynthesis models. The sharp decline in abundances beyond Zr disfavors neutron star merger or electron-capture supernova models, but is reproduced either by protoneutron star wind models or by magneto-rotational supernova models. Considering the high [Zn/Fe] ratio, a magnetorotational supernova is the most plausible origin of SMSS 0224─5737. This study demonstrates that the abundance measurements of both light and neutron-capture elements, even at low abundances, are crucial for unveiling the astrophysical sites of the weak r-process.

Keywords: Nucleosynthesis, Stellar abundances, R-process, Population II stars, Chemically peculiar stars
Modeling APOKASC-3 Red Giants. I. The First Dredge-up and Red Giant Branch Bump. We focus on two key diagnostics of stellar physics in red giant branch (RGB) stars: the first dredge-up (FDU) of nuclear processed material and the location of the RGB bump (RGBB). We compare asteroseismic and spectroscopic APOKASC-3 data with theoretical MESA models. Our FDU predictions have similar mass and metallicity trends to the data, but the observed magnitude of the change in [C/N] in data is smaller than theoretical predictions by [0.1615 ± 0.0760 (obs) ± 0.0108 (sys)] dex. These results are insensitive to the input physics, but they are at a level consistent with systematic uncertainties in the abundance measurements. When we include observed trends in birth [C/Fe] and [N/Fe] in our models, it modestly increases the metallicity-dependent difference relative to the data. We find a well-defined empirical RGBB locus:  logg=2.6604−0.1832(M/M⊙−1)+0.2824[Fe/H] . Our model RGBB loci have mass and composition trends that mirror the data, but we find that the observed RGBB is [0.1509 ± 0.0017 (obs) ± 0.0182 (sys)] dex higher than predicted across the board, similar to prior literature results. We find that envelope undershooting, a proposed solution to reconcile theory with data, increases Li destruction during the FDU at higher metallicities, creating tension with depletion observed in GALAH data. We propose Li in the FDU as a sensitive test of the RGBB and FDU, and discuss other potential solutions.

Keywords: Galaxy chemical evolution, Dredge-up, Stellar evolutionary models, Red giant stars, Red giant bump
Explosions in the Empty: A Survey of Transients in Local Void Galaxies. We present a systematic analysis of transient astrophysical events—including supernovae (SNe), gamma-ray bursts (GRBs), and fast radio bursts (FRBs)—in void and nonvoid galaxies within the local Universe (0.005 &lt; z &lt; 0.05). Cosmic voids, defined by low galaxy densities and characterized by minimal environmental interactions, offer a natural laboratory for isolating the impact of large-scale underdensities on stellar evolution and transient production. Using multiwavelength data from the Sloan Digital Sky Survey, the Sternberg Astronomical Institute Supernova Catalogue, and high-energy space observatories, we compare transient occurrence rates and host galaxy properties across environments. We find that core-collapse SNe are significantly more common in void galaxies, indicating that massive star formation remains active in underdense regions. In contrast, Type Ia SNe are less frequent in voids, consistent with a scarcity of older stellar populations. Notably, we identify a short-duration GRB hosted by a void galaxy, demonstrating that compact object mergers can occur in isolated environments. Additionally, we find no FRBs associated with void galaxies. Taken together, these results show that cosmic voids exert a measurable influence on the star formation history of galaxies and hence on the production of transients.

Keywords: Gamma-ray bursts, Voids
Orbital Parameter Estimation from X-Ray/Optical Echo Mapping in X-Ray Binaries. Determination of X-ray binary system parameters informs a wide range of astrophysical investigations, including the formation and evolution of stellar populations, and the accretion/outflow process itself. However, interpretation of radial velocity signals is challenged by the complicated nature of the emission sites in the systems. X-ray/optical light echoes—in which X-ray emission from the vicinity of the compact object heats the surface of the donor, resulting in delayed optical emission—offers a separate route for establishing constraints on the system parameters. This method has already been employed to set limits on binary parameters in some systems. We present a practical Bayesian technique to constrain the credible ranges of X-ray binary orbital parameters, using observations of the time delay in these geometry-dependent X-ray/optical correlations. Parameters are conditioned on the data with the widely used and well-tested emcee Markov Chain Monte Carlo ensemble sampler to chart the joint posterior distribution of the system parameters. The potential of this echo-delay technique is demonstrated by recovering credible ranges of orbital parameters from synthetic test-case observations. Additionally, real echo delay and radial velocity data from the systems Sco X-1 and 4U 1636-536 are analyzed with our method, producing joint posterior probability distributions for the orbital parameters. We find that in certain cases our echo-delay method is able to break the mass─inclination degeneracy intrinsic to investigations using radial velocity data alone. We release our software to the community, and include a replication module so that the interested reader may reproduce our findings.

Keywords: X-ray astronomy, X-ray binary stars, Public domain software, Astronomical techniques, Stellar masses, Markov chain Monte Carlo, Time series analysis
Mapping the Cosmic-Ray Ionization Rate in the Local Galaxy with <inline-formula> <mml:math><mml:msubsup><mml:mrow><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math> </inline-formula>. Chemistry in diffuse molecular clouds relies primarily on rapid ion-molecule reactions. Formation of the initial ions, H+ and H 2+ , is dominated by cosmic-ray ionization of H and H2, making the cosmic-ray ionization rate (denoted ζ(X) for species X) an important parameter for chemical modeling. We have made observations targeting absorption lines of H 3+ , one of the most reliable tracers of ζ(H2), toward diffuse molecular cloud sight lines where the H2 column density has been directly measured in the ultraviolet, detecting H 3+  in 12 out of 27 sight lines. The 3D-PDR modeling method introduced by M. Obolentseva et al. was used to infer cosmic-ray ionization rates in the clouds along these sight lines, and our combined sample has a mean ionization rate of 5.3 × 10−17 s−1 with standard deviation 2.5 × 10−17 s−1. By associating H 3+  absorption with gas density peaks derived from the differential extinction maps of G. Edenhofer et al., we have constructed a sparsely sampled 3D map of the cosmic-ray ionization rate in targeted regions within about 1 kpc of the Sun. Specific regions show reasonably uniform ionization rates over length scales of tens of parsecs, with the average ionization rate in each region being different. Large differences (factor of 5) in ζ(H2) are found over length scales of about 100 pc. This supports a picture where the cosmic-ray ionization rate varies smoothly over small size scales, but is not uniform everywhere in the Galactic disk, likely being controlled by proximity to particle acceleration sites.

Keywords: Galactic cosmic rays, Interstellar absorption, Diffuse molecular clouds, Interstellar medium
Magnetic White Dwarf─M Dwarf Binaries in Pre-mCV Phase as Special Population of Long-period Radio Transients. Long-period radio transients (LPTs) are a new class of coherent radio sources with periods ranging from minutes to hours. Recently, two LPT sources, ILT J1101+5521 and GLEAM-X J0704─37, with periods of 2─3 hr have been confirmed to originate from white dwarf (WD)─M dwarf (MD) binaries. In this work, we propose that at least some LPTs originate from the magnetic WD─MD binaries in the pre-magnetic cataclysmic variables (pre-mCV) phase. The asynchronism between the WD's rotation and the binary's orbital motion allows for the unipolar-inductor mechanism or magnetosphere-interaction to operate and accelerate radiating particles, with the dominant process depending on the magnetic moment ratio of the two stars. Under an asynchronism condition, both the peak flux and the polarization of radio pulses will be modulated by the beat period. The pre-mCV phase characterized by an extremely low-accretion rate provides the relatively clean magnetospheric environment necessary for an LCDM mechanism to operate, producing the LPT emission. The observed pulse duty cycle of 10−3−10−1 is attributed to a beaming effect modulated by the binary's magnetic geometry. Furthermore, the magnetized environment of a WD─MD binary is conducive to Faraday conversion with weak coupling, which implies that the polarization state of LPTs should vary significantly at different periods. Finally, we predict that LPTs from WD─MD binaries should exhibit a period distribution following fP(P)dP ∝ P(1.67−2.33)dP and a luminosity function described by fL(L)dL ∝ L−(1.80−2.67)dL, which can be tested by the future large sample.

Keywords: High energy astrophysics, Compact radiation sources, Close binary stars, Non-thermal radiation sources, Radio transient sources
Which Active Galaxies Might be Neutrino Emitters?. The IceCube Neutrino Observatory has identified several individual neutrino emitters associated with supermassive black hole accretion phenomena, including blazars, tidal disruption events, and, unexpectedly, Seyfert galaxies. A key open question is which types of active galactic nuclei (AGNs) are most likely to be neutrino emitters. Here we show that high-confidence extragalactic neutrino emitters tend to not only have higher hard X-ray fluxes but also be more variable in mid-infrared (MIR) than other AGNs in the Swift BAT AGN Spectroscopic Survey. MIR variations effectively trace long-term fluctuations in AGN accretion disks and/or jets. In addition to the role of X-ray flux emphasized in previous studies, we speculate that long-term central engine fluctuations may also be critical for neutrino production. This hypothesis may inform IceCube neutrino-electromagnetic counterpart association studies and provide new insights on cosmic-ray acceleration sites. First, the observed neutrinos are unlikely to originate from AGN host galaxies or from interactions between large-scale (dozens of parsecs) winds/outflows and the surrounding interstellar medium. Second, if neutrinos are produced in the X-ray corona, the corona should exhibit strong magnetic turbulence dissipation or magnetic reconnection whose rate changes substantially on timescales of years. Third, the relativistic jets of blazar neutrino emitters may be intrinsically unstable over years. Finally, if neutrinos are related to interactions between small-scale winds/outflows and torus clouds, such winds/outflows must be highly episodic.

Keywords: Neutrino astronomy, Active galactic nuclei, Time domain astronomy, High energy astrophysics
The Size Evolution and the Size─Mass Relation of Lyα Emitters across 3 ≲ z&lt; 7 as Observed by JWST. Understanding the morphological structures of Lyα emitters (LAEs) is crucial for unveiling their formation pathways and the physical origins of Lyα emission. However, the evolution of their sizes and structural scaling relations remains debated. In this study, we analyze a large sample of 876 spectroscopically confirmed LAEs at 3 ≲ z &lt; 7, selected from the MUSE, VANDELS, and CANDELSz7 surveys in the GOODS-S, Ultra Deep Survey, and COSMOS fields. Utilizing James Webb Space Telescope NIRCam imaging data, we measure their rest-frame UV and optical V-band effective radii (Re) through two-dimensional Sérsic profile fitting. Our results show that these LAEs are generally compact, with a median Re,UV of 0.50 −0.24+0.30  kpc and a median Re,V of 0.57 −0.24+0.33  kpc. The size evolution follows Re,UV ∝ (1 + z)−0.91±0.10 and Re,V ∝ (1 + z)−0.93±0.18, respectively. Their UV and optical sizes are statistically comparable, indicating negligible UV-to-optical color gradients. For the first time, we establish the rest-frame optical size─mass relation for LAEs at z &gt; 3, finding slopes comparable to typical star-forming galaxies, but with slightly smaller sizes at a given stellar mass. These results provide important clues for understanding the structural evolution of LAEs in the early Universe.

Keywords: Lyman-alpha galaxies, High-redshift galaxies, Galaxy evolution
Toward Understanding the Origin of Swift Gamma-Ray Bursts Driven by Magnetars. In this paper, we analyze a sample of Swift gamma-ray bursts (GRBs) with extended emissions in γ-rays and/or X-ray plateaus that may be driven by magnetars. Multiwavelength data and multistandards have been adopted to investigate the issue jointly. First, we find that GRBs with both extended emission and X-ray plateau satisfy a three-parameter relation between the luminosity and the end time of X-ray plateaus and the γ-ray isotropic energy as  LX∝Ta−1.13Eγ,iso0.74 , which is consistent with that of normal GRBs. Second, we distinguish these GRBs in the plane of magnetic field versus period of neutron star and find that almost all GRBs, except GRB 211024B, have reasonable periods, and the majority of them could be powered by magnetars. Third, we standardize the X-ray afterglows with distinct characteristics and find that the standard X-ray light curves with/without plateaus are significantly different. The standardized X-ray plateaus are similar to the mean temporal profile of magnetars. Fourth, it is verified with a K-S test that all types of GRBs except short ones have similar distributions of redshift and isotropic energy in the observer/rest frame. GRBs with internal plateaus are significantly different from those of normal long GRBs and GRBs with external plateaus and/or extended emissions. Interestingly, the isotropic energy distributions of GRBs with internal and external plateaus are identical with those of short and long GRBs, respectively. Overall, our study can bring solid evidence that the fascinating magnetars could have multiformation channels to account for not only short but also long GRBs with either internal or external X-ray plateaus as well.

Keywords: Gamma-ray bursts
A Leptonic Interpretation of the Ultra-high-energy Gamma-Ray Emission from V4641 Sgr. Recently, the microquasar V4641 Sgr and its surrounding have been detected at TeV─PeV gamma-ray band. Interestingly, the spectrum follows a power-law function continuing up to 0.8 PeV as reported by LHAASO, and the morphology of the emission appears to be a puzzling elongated structure. In this work, we propose that the elongated ultra-high-energy (UHE) emission from V4641 Sgr could originate from the inverse Compton radiation of electrons with a very hard spectrum, which may result from shear acceleration mechanism in the jets driven by V4641 Sgr. We also calculate the corresponding X-ray synchrotron emission from the same electron population, predicting the potential range of nonthermal X-ray flux of the source. The recent observation by XRISM toward the central part of the UHE source could pose a constraint on the model's parameters. In the future, a full coverage of the source by sensitive X-ray instruments and high-resolution TeV─PeV gamma-ray instruments may provide a critical test of the model.

Keywords: Gamma-ray sources, Jets, Non-thermal radiation sources, Cosmic ray sources
Kinematic Ages of the Tucana─Horologium, Columba, and Carina Associations. The traceback method allows the computation of the kinematic age of nearby young associations from astrometric and kinematic data alone, circumventing the need for stellar evolution models. Previous traceback age estimates have, however, often been incompatible with other age-dating methods. We apply the Kinematic Age for Nearby Young Associations traceback analysis tool on core samples, free of contaminants such as unresolved multiple systems, of carefully vetted members of the Tucana─Horologium (THA), Columba (COL), and Carina (CAR) associations, using data from Gaia Data Release 3 (DR3) data products and other kinematic surveys, in order to test whether the traceback method can be used successfully on 40─50 Myr old associations. Due to the lack of a clear boundary between members of COL and CAR, these two associations were combined in a single sample for the purpose of our analysis. Several systematic biases, including gravitational redshift, convective blueshift, and the bias on traceback ages due to random measurement errors, are accounted for. We find that the mean length of all branches between members and the trace of the  ξ'η'ζ'  spatial covariance matrix are the most robust and generalizable association size metrics among those that were tested. We obtain reliable constraints on the traceback ages:  44.8−7.0+2.1  Myr for THA, and  28.4−2.9+1.8  Myr for COL and CAR. These results are compatible with previous age estimates for THA, COL, and CAR computed with the isochrones and lithium depletion boundary methods.

Keywords: Stellar kinematics, Young star clusters, Stellar ages, Stellar associations