Sazuna/UAT_keywords huggingface dataset:
Testing the Physical Parameter Constraining Power of HCN and HNC with Neural Networks. We quantify the utility of HCN and HNC to characterize gas conditions in the nearby starburst galaxy NGC 253. We use measurements from the Atacama Large Millimeter/Submillimeter Array (ALMA) Large Program ALCHEMI: the ALMA Comprehensive High-resolution Molecular Inventory. Using different subsets of the eight total HCN and HNC transitions measured by ALCHEMI, we test the number and combinations of transitions necessary for constraining the temperature, H2 volume and column densities, cosmic-ray ionization rate, and beam-filling factor in three representative regions within NGC 253. We use these combinations of HCN and HNC transitions to constrain chemical and radiative transfer models, and infer the gas conditions using a Bayesian nested sampling algorithm combined with neural network models for increased efficiency. By comparing the shapes of the resulting posterior distributions, as well as the medians and uncertainties for each gas parameter, from each test case to what we obtain with the full set of eight transitions (the control), we quantify how well each test reproduces the control. We find that multiple transitions each of both molecules are required to obtain a median parameter value within a factor of 2 of the control with an uncertainty less than 2─3 times that of the control. We also find that transition combinations which feature a range of upper-state energies are most effective. We show that single transitions, such as HCN J = 1─0 or 3─2, are among the worst-performing combinations and result in parameter values up to an order of magnitude different than the control.

Keywords: Molecular gas, Starburst galaxies, Bayesian statistics, Neural networks, Star forming regions, Giant molecular clouds, Interstellar medium
Multimessenger Modeling of Low-luminosity γ-Ray Bursts. Low-luminosity γ-ray bursts (LL GRBs), a subclass of the most powerful transients in the Universe, remain promising sources of high-energy astrophysical neutrinos, despite strong IceCube constraints on typical long GRBs. In this work, a novel approach is introduced to study a sample of seven LL GRBs with their multiwavelength observations to investigate leptohadronic processes during their prompt emission phases. The relative energy densities in magnetic fields, nonthermal electrons, and protons are constrained, with the latter defining the cosmic-ray (CR) loading factor. Our results suggest that LL GRBs exhibit diverse emission processes, as confirmed by a machine learning analysis of the fitted parameters. Across the seven LL GRBs, we find the posterior medians of the CR loading factor to be in the range of ξp ∼ 0.2─1.6. GRB 060218 and GRB 100316D, the lowest-luminosity bursts (Lγ,iso ∼ 1046─1047 erg s−1) consistent with the shock-breakout scenario, yield the highest CR loading factors and therefore are expected to produce neutrinos more efficiently. Our model predicts the expected number of neutrino signals that are consistent with current limits but would be detectable with next-generation neutrino observatories. These results strengthen the case for LL GRBs as promising sources of high-energy astrophysical neutrinos and motivate real-time searches for coincident LL GRB and neutrino events. Next-generation X-ray and MeV facilities will be critical for identifying more LL GRBs and strengthening their role in multimessenger astrophysics.

Keywords: Gamma-ray bursts, High energy astrophysics, Neutrino astronomy, Transient sources, Burst astrophysics, Particle astrophysics
Investigating FRB 20240114A with FAST: Morphological Classification and Drifting Rate Measurements in a Burst-cluster Framework. This study investigates the morphological classification and drifting rate measurement of the repeating fast radio burst (FRB) source FRB 20240114A using the Five-hundred-meter Aperture Spherical Telescope. Detected on 2024 January 14, FRB 20240114A exhibited an exceptionally high burst rate, revealing unique properties. Through observational campaigns over several months, we selected a data set comprising 3203 bursts (2109 burst clusters) during a continuous monitoring session (15,780 s) on 2024 March 12. Improving upon previous work, we clarify the definitions of sub-bursts, bursts, and burst clusters. Using an average dispersion measures of 529.2 pc cm−3, we classified the burst clusters into Downward Drifting, Upward Drifting, No Drifting, No Evidence for Drifting, Not-Clear, and Complex burst clusters. Among the 978 burst clusters that exhibit drifting behavior, 233 (23.82%) show upward drifting. Additionally, if 142 upward-drifting single-component burst clusters are excluded, upward-drifting double- and multicomponent burst clusters still account for 10.89% of the 836 burst clusters exhibiting drifting behavior, equating to 91 burst clusters. Furthermore, if only upward-drifting burst clusters with consecutive time intervals (or upward-drifting bursts) are considered, only nine bursts remain. Drifting rate comparisons with other physical quantities reveal that the drifting rate increases with peak frequency for single-component burst clusters with drifting behavior. Moreover, in single-component burst clusters, those with upward drifting exhibit smaller effective widths, bandwidths, and fluxes than their downward-drifting counterparts. A Kolmogorov─Smirnov test further indicates that upward-drifting burst clusters possess longer consecutive time intervals than downward-drifting ones, suggesting distinct underlying physical mechanisms.

Keywords: High energy astrophysics, High time resolution astrophysics, Radio bursts, Radio astronomy, Radio transient sources
ALMA Observations of Cold Methanol Gas in the Large Magellanic Cloud: N79 South Giant Molecular Cloud. We report Atacama Large Millimeter/submillimeter Array continuum and molecular line observations at 0.1 pc resolution toward the super star cluster (SSC) candidate H72.97−69.39 in the N79 region of the LMC. The continuum emission has a sharp peak around the SSC candidate but is also widely distributed. We identify two continuum sources at the northern (N79S-1) and northwestern (N79S-2) positions of the SSC continuum peak, associated with CH3OH emission. In addition to CH3OH, we also detect H2CO, H2CS, CS, SO, CO, CN, and CCH at the positions of N79S-1 and N79S-2. The rotation diagram analysis of CH3OH and SO lines yields an average gas temperature of 13 ± 0.4 K for N79S-1 and 15 ± 0.9 K for N79S-2. Most emission lines exhibit line widths of less than 2.8 km s−1, consistent with emissions from cold, dense molecular cloud cores. The abundance of cold CH3OH gas is estimated to be (2.1 ± 1.1) × 10−9 at N79S-1 and (4.5 ± 2.5) × 10−10 at N79S-2. Despite the lower metallicity in the LMC, the CH3OH abundance at N79S-1 is comparable to that of similar cold sources in our Galaxy. However, the formation of organic molecules is inhibited throughout the N79 regions, as can be seen in the nondetection of CH3OH in most of the regions. The two positions N79S-1 and N79S-2 would be exceptional positions, where CH3OH production is efficient. The possible origins of cold CH3OH gas in these dense cores are discussed, along with a possible explanation for the nondetection of CH3OH in the SSC candidate.

Keywords: Interstellar molecules, Astrochemistry, Star formation, Interstellar medium, Protostars, Magellanic Clouds
SDSS-V LVM: Collisionless Shocks in the Supernova Remnant RCW86. The supernova remnant (SNR) RCW86 is among the few SNRs with Balmer-emission lines containing broad and narrow spectral components that trace fast, nonradiative shocks in partially ionized gas. These are invaluable laboratories for collisionless shock physics, especially for poorly understood phenomena like electron-ion equilibration, and shock precursors. Here we present the first ∼0.3 pc spatial scale integral field unit observations of the southwestern RCW86 shock, obtained as part of the Sloan Digital Sky Survey-V Local Volume Mapper (LVM). The forward shock, clearly visible as thin filaments in narrowband images, exhibits broad component Hα emission, indicating shock velocities varying from 500─900 km s−1 in the south to 1000─1500 km s−1 in the north. The varying velocity widths and broad-to-narrow intensity ratios show that electrons and ions have lower equilibration (Te/Tp → 0.1) in faster (&gt;800 km s−1) shocks, in line with previous studies. The broad components are generally redshifted from the narrow components by ≲100 km s−1, likely due to shock-obliquity or non-Maxwellian post-shock distributions. We observe high extinction-corrected Balmer-decrements of 3─5 in the narrow components, indicating that conversion of Lyβ photons to Hα is more efficient than Lyγ to Hβ. Upper limits on the He IIλ4686 in the southern shock are consistent with a moderate-to-high (30%─100%) neutral fraction in the preshock gas. We also find the first evidence of an intermediate Hα component in RCW86, with ∆V(FWHM) = 193─207 km s−1, likely due to a fast neutral precursor. We also briefly discuss the southwestern radiative shock, and lay out the exciting future of studying astrophysical shocks with LVM.

Keywords: Supernova remnants, Emission nebulae, Interstellar medium, Shocks, Supernovae
The [Fe XIII] Infrared 10747 and 10798 Å Lines in Novae. The forbidden lines of [Fe XIII] at 10747 and 10798 Å are among the most prominent lines in the near-infrared spectrum of the solar corona. They have been used routinely, both outside and during eclipses, as sensitive probes of the electron density and polarization in the solar corona. Many novae pass through a coronal phase, wherein the highly ionized nova ejecta have physical conditions that are remarkably similar to those of the solar corona. Many of the coronal emission lines that are seen are common to the spectra of both the Sun and novae. Yet, it appears that no robust detection of the [Fe XIII] lines has been made in a nova. Here we report the detection of these two infrared [Fe XIII] lines in the spectrum of the recurrent nova V3890 Sgr, taken 23.43 and 31.35 days after its 2019 August outburst. From their line strengths, we derive values of 1010 and 10[8.5−9] cm−3 for the electron density on the two epochs. The decrease in density between epochs can be explained if the density decreased with a power law n(r) ∝ rα, with α inferred to be −3. The average temperature of the coronal gas is estimated to be T = (2.51 ± 0.06) × 106 K. We find that recurrent novae with giant secondaries, including T CrB, whose eruption is imminent, are the most suitable sources for further detections of the [Fe XIII] lines.

Keywords: Infrared spectroscopy, Novae, Recurrent novae, Circumstellar gas, Stellar coronal lines, Near infrared astronomy
The Fate of Gaia's Wide Binaries: Interplay of White-dwarf Recoil and Tidal Interactions. White dwarfs (WDs) receive natal velocity boosts of ∼1 km s−1 due to recoil from asymmetric mass loss during the late asymptotic giant branch (AGB) stage. In a wide binary, the acceleration of a WD progenitor exerts a torque, modifying the orbital eccentricity. Potential signatures of this effect have been detected in Gaia's wide binary sample. At the same time, an AGB star's puffy envelope facilitates strong tidal interactions in binaries with periapsis separations of a few astronomical units, capturing the companion into a tighter orbit and potentially driving the system towards a common-envelope phase. Using an analytical model for wide binary evolution under asymmetric AGB mass loss, we predict the eccentricity distribution of wide WD+MS and WD+WD binaries. We find that recoil can induce tidal interactions in up to ∼40% of initially wide binaries on the AGB or post-AGB for initial separations of ∼100─1000 au. We relate these interactions to three recent observational puzzles: (i) the dearth of wide WD+MS and WD+WD binaries in Gaia DR3 with eccentricities ≳0.9; (ii) the formation of moderately eccentric WD+MS and WD+WD binaries with orbital periods of ∼100─1000 days, which we suggest happens via a high-eccentricity common-envelope phase induced by recoil; and (iii) the origin of low-luminosity, long-timescale, dust-obscured transients towards AGB progenitors, such as the ongoing event WNTR23bzdiq in M31. Our findings have potential implications for the survival and dynamical evolution of planetary systems around WD progenitors, to be investigated in future works.

Keywords: Wide binary stars, White dwarf stars, Common envelope evolution, Stellar mass loss
Effects of Numerical Resolution on Simulated Cloud─Wind Interactions. Mixing by hydrodynamical instabilities plays a key role in cloud─wind interactions, causing cloud destruction in the adiabatic limit and facilitating cloud survival with efficient radiative cooling. However, the rate of mixing in numerical simulations is sensitive to the smallest resolved scale, and the relationship between resolution and cloud evolution is underexplored. Using a set of cloud-crushing simulations, we investigate the effects of numerical resolution on cloud survival and acceleration. Modeling both adiabatic and radiative cases, in a subsonic and supersonic wind, we find that cloud survival and velocity depend on the numerical resolution; however, no single resolution requirement can be applied to all scenarios. In the radiative subsonic case, we find that mass growth and acceleration appear converged at only 4 cells per cloud radius. Conversely, in the supersonic regime, we see a clear dependence of cloud destruction and velocity on resolution that is not converged even at 48 cells per cloud radius, implying that accurately capturing cloud destruction may require higher resolution than capturing growth. We also present a simple model illustrating how ram pressure accelerates cool clouds at early times before mixing kicks in as an acceleration mechanism.

Keywords: Galactic winds, Astrophysical fluid dynamics, Interstellar clouds, Circumgalactic medium
The Structure and Kinematics of Three Class 0 Protostellar Jets from JWST. We present observations of jets within 2000 au of three deeply embedded protostars using 2.9─27 μm observations with JWST. These observations show the morphologies and kinematics of the collimated jets from three protostars, the low-mass Class 0 protostars B335 and HOPS 153, and the intermediate-mass protostar HOPS 370. These jets are traced by shock-ionized fine-structure line emission observed with the JWST NIRSpec and MIRI integral field units. We find that [Fe II] emission traces the full extent of the inner 1000─2000 au of the jets, depending on the distance to the protostar, while other ions mostly trace isolated shocked knots. The jets show evidence of wiggling motion in the plane of the sky as well as asymmetries between blue- and redshifted lobes. The widths of the jets increase nonmonotonically with distance from the central protostar, with opening angles ranging from  2.°1  to  &lt;10.°1  for the three protostars in the sample. The jets have total velocities ranging from 147 to 184 km s−1 after correcting for disk inclination. For B335, an 8 month gap between NIRSpec and MIRI Medium Resolution Spectroscopy observations enabled measurement of the tangential velocity of a shocked knot; in combination with the radial velocity, this shows that the jet has a different inclination than the outflow cavity. We find multiple knots before and during a recent outburst in B335, although the knots were more frequent during the burst. The asymmetries between the blue- and redshifted lobes strongly suggest complex interactions between the circumstellar disks and magnetic fields.

Keywords: Protostars, Young stellar objects, Jets
Primitive Crust Buried Below the Southern Highland of Mars. Geochemical studies of shergottites have predicted an enriched end member associated with the final residual liquid of the Martian magma ocean, which may result in the formation of a KREEP-like silica-rich primitive crust on early Mars. In this work, we investigate the evolution of the Martian crust using the 1D parameterized mantle convection model. By combining various observational and geophysical constraints, our model supports the KREEP-like silica-rich primitive crust that formed before 4.527 Ga, i.e., the time for the formation of the earliest basaltic secondary crust associated with the early mantle overturn, whose thickness would be at least 3─8 km. During the consequential evolution, the silica-rich primitive crust on the northern hemisphere would have been removed by the Borealis impact. However, the silica-rich primitive crust of the southern hemisphere would still survive and would be buried below the ejecta of the Borealis impact and local basaltic secondary crust, which may correspond to the low-density layer below the southern highland of Mars suggested by gravitational observations.

Keywords: Mars, Planetary interior, Mantle
Coronal Hole Boundary Region: Multiple Facets and Connection to the Slow Solar Wind. It is commonly recognized that a coronal hole (CH) boundary region exists where the slow solar wind (SW) is formed by more than one physical process. The physical properties at the CH boundary region play an important role in dictating the slow SW properties by providing conditions for the relevant processes to work upon. However, how the CH boundary region is defined is still a work under debate. We present investigations on two large CHs that crossed the central meridian during 2015 August 17─21. We use imaging, spectroscopic and photospheric magnetic field observations by Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly, Hinode/Extreme-ultraviolet Imaging Spectrometer, and SDO/Helioseismic and Magnetic Imager to investigate the spatial and temporal variation in coronal emission, electron temperature, and the photospheric magnetic field across the CH and its vicinity to search for how a CH boundary region can be defined. The collective evidence from this study suggests that the CH/open field area is significantly larger than what is commonly identified by CH identification schemes. We find that the coronal line intensity at the peak of its intensity distribution within an area enclosing the CH and nearby quiet Sun/active region structures is a good indicator for the outer CH boundary where the mostly open field area meets with the quiet Sun/active region dominated by close loops. We discuss the role of this CH boundary region in the slow SW formation. The results also provide a solution for alleviating the open flux problem and serve as an empirical constraint for refining global coronal field models.

Keywords: Slow solar wind, Solar magnetic reconnection, Solar extreme ultraviolet emission, Solar wind, Solar coronal lines, Solar corona, Solar magnetic fields, Solar coronal holes
JWST Reveals a Candidate Jellyfish Galaxy at z = 1.156. We report the discovery of COSMOS2020-635829 as a candidate jellyfish galaxy undergoing ram pressure stripping in a (proto)cluster at z &gt; 1. High-resolution imaging from the James Webb Space Telescope reveals a symmetric stellar disk coupled to a unilateral tail of star-forming knots to the south. Using Gemini GMOS integral field unit (IFU) observations, we show that these extraplanar continuum sources are embedded within an ionized gas tail that is kinematically connected to the disk of COSMOS2020-635829. If confirmed, this represents the highest-redshift discovery of a ram-pressure stripped ionized gas tail. The tail sources are characterized by extremely young stellar populations (≲100 Myr), have stellar masses of ∼108 M⊙, and star formation rates of 0.1─1 M⊙ yr−1. This work shows that ram-pressure stripping can potentially perturb group and cluster galaxies at z &gt; 1 and may contribute to environmental quenching even near Cosmic Noon.

Keywords: Galaxy clusters, High-redshift galaxy clusters, Ram pressure stripped tails, Galaxy tails, Star formation, Galaxy evolution, Galaxy groups, Galaxy spectroscopy
The Tantalizing Case of the Quasar J0950+5128. I. Presentation of the Data and Detailed Exploration of the Binary Supermassive Black Hole Scenario. Spectroscopic observations of the quasar J0950+5128 spanning 22 yr reveal monotonic radial velocity variations in its broad Hβ emission line. Moreover, the line profile becomes broader over time, necessitating careful measurements. We present robust Hβ velocity shift measurements obtained via cross correlation, applied to both the full spectra and to isolated broad Hβ components derived from spectral decomposition. We also examine the light curves for variability consistent with the spectroscopic trends. Using Lomb─Scargle periodogram analysis, we find no significant periodic signal. We consider several interpretations for the observed changes, including a binary supermassive black hole, dust-cloud obscuration, outflows, a recoiling black hole, and a single perturbed, disk-like broad-line region (BLR). We deem the binary and perturbed BLR scenarios to be physically plausible. The binary interpretation is the only one for which we can immediately compare a physical model to the available data. Thus, we incorporate radial velocity "jitter" to emulate typical quasar variability and fit the radial velocity curve with a Keplerian model to examine whether it can reproduce the observations. In this context, the available observations trace only a segment of the putative orbit. The fit yields a period of 33 yr (observed frame) and an eccentricity of 0.65, with lower limits on the semimajor axis and black hole mass of 10−2 pc and 107 M⊙, respectively. Thus, J0950+5128 is a binary candidate deserving further study. The single, perturbed BLR interpretation remains viable but requires additional observations and modeling for further evaluation. Continued monitoring is, therefore, essential.

Keywords: Supermassive black holes, Active galactic nuclei, Quasars
Multiwavelength Study of a Superflare on RS CVn─Type Star HD 22468 Triggered at Hard X-Ray by SVOM. Detection of stellar flares at hard X-ray is still rare at the current stage. A transient was recently detected by the hard X-ray camera ECLAIRs on board the SVOM mission at 11:39:01.2 UT on 2025 January 09. Simultaneous monitoring in the optical band on the ground by SVOM/GWAC and follow-up spectroscopy enabled us to confirm that the transient is caused by a superflare on HD 22468, an RS CVn─type star. The bolometric energy released in the flare is estimated to be ∼7.2 × 1037─1.7 × 1038 erg. The hard X-ray spectra of the event at the peak can be reproduced by the "apec" model of a hot plasma with a temperature of  106−22+27  MK. In the optical range, the Hα emission-line profile obtained at ∼1.7 hr after the trigger shows a bulk blueshift of −96 ± 20 km s−1, which can be explained by either a chromospheric evaporation or a prominence eruption. The ejected mass is estimated to be 3.9 × 1020 g for the evaporating plasma and to be 3.2 × 1021 g &lt; Mp &lt; 8.8 × 1021 g for the erupted prominence.

Keywords: Stellar x-ray flares, Gamma-ray sources, Stellar chromospheres, Stellar flares, Spectroscopy, RS Canum Venaticorum variable stars