Sazuna/UAT_keywords huggingface dataset:
XMM-Newton Observations of the High Temperature Plasma in the Large Magellanic Cloud Supernova Remnant N132D. We present an analysis of the archival XMM-Newton observations of the Large Magellanic Cloud (LMC) supernova remnant N132D totaling more than 500 ks. We focus on the high temperature plasma (kTe ∼ 4.5 keV) that is responsible for the high energy continuum and exciting the Fe K emission. An image analysis shows that the Fe K emission is mainly concentrated in the southern part of the remnant interior to the region defined by the forward shock. This Fe K distribution would be consistent with an asymmetric distribution of the Fe ejecta and/or an asymmetric interaction between the reverse shock and the Fe ejecta. We compare the EPIC-pn and EPIC-MOS spectra in the 3.0─12.0 keV bandpass with a model based on RGS data plus a higher temperature component, in collisional ionization equilibrium (CIE), or nonequilibrium (both ionizing and recombining). We find that the data are equally well fitted by the CIE and ionizing models. Assuming the CIE and ionizing spectral models, the Fe in this high temperature component is significantly enhanced with respect to typical LMC abundances. We can place only an upper limit on the neutral Fe K line. We conclude that the Fe K emission is due to ejecta heated by the reverse shock given the spatial distribution, relatively high temperature, and enhanced abundance. We estimate the progenitor mass based on the Ca/Fe and Ni/Fe mass ratios to be 13 ≤ MP ≤ 15M⊙.

Keywords: Supernova remnants, X-ray astronomy, Core-collapse supernovae
Cue: A Fast and Flexible Photoionization Emulator for Modeling Nebular Emission Powered by Almost Any Ionizing Source. The complex physics governing nebular emission in galaxies, particularly in the early Universe, often defy simple low-dimensional models. This has proven to be a significant barrier in understanding the (often diverse) ionizing sources powering this emission. We present Cue,10 10Cue v0.1 is available online at GitHub, https://github.com/yi-jia-li/cue with a copy deposited to Zenodo (Y. Li et al. 2024). a highly flexible tool for interpreting nebular emission across a wide range of abundances and ionizing conditions of galaxies at different redshifts. Unlike typical nebular models used to interpret extragalactic nebular emission, our model does not require a specific ionizing spectrum as a source, instead approximating the ionizing spectrum with a four-part piecewise power law. We train a neural net emulator based on the CLOUDY photoionization modeling code and make self-consistent nebular continuum and line emission predictions. Along with the flexible ionizing spectra, we allow freedom in [O/H], [N/O], [C/O], gas density, and total ionizing photon budget. This flexibility allows us to either marginalize over or directly measure the incident ionizing radiation, thereby directly interrogating the source of the ionizing photons in distant galaxies via their nebular emission. Our emulator demonstrates a high accuracy, with ∼1% uncertainty in predicting the nebular continuum and ∼5% uncertainty in the emission lines. Mock tests suggest Cue is well calibrated and produces useful constraints on the ionizing spectra when the signal-to-noise ratio of Hα is ≳10, and furthermore capable of distinguishing between the ionizing spectra predicted by single and binary stellar models. The computational efficiency of neural networks facilitates future applications of Cue for rapid modeling of the nebular emission in large samples and Monte Carlo sampling techniques. Cue v0.1 is available online at GitHub, https://github.com/yi-jia-li/cue with a copy deposited to Zenodo (Y. Li et al. 2024).

Keywords: Photoionization, Stellar populations, Active galactic nuclei, Galaxy evolution, Interstellar medium, H II regions
Thermal Desorption Kinetics, Binding Energies, and Entrapment of Methyl Mercaptan Ices. Organosulfur species are potential major carriers of sulfur in the interstellar medium, as well as interesting ingredients in prebiotic chemistry. The most fundamental question regarding these species is under which conditions they reside in the gas versus solid phase. Here, we characterize the thermal desorption kinetics, binding energies, and entrapment of the organosulfur methyl mercaptan (CH3SH, or MeSH) in different ice environments, comparing them with those of methanol (CH3OH, or MeOH) ices. The derived multilayer (pure MeSH–MeSH) and submonolayer (layered MeSH–H2O) binding energies are surprisingly similar, corresponding to snow line locations where the disk midplane temperature is ∼105 K. In both H2O-dominated and more realistic H2O:CO2-dominated ices, 100% of the MeSH is entrapped, almost exclusively desorbing at the molecular volcano desorption peak, indicating that MeSH is retained at the water snow line if initially mixed with water ice during formation. Additionally, the presence of MeSH in an ice mixture enhances the entrapment of CO2 and MeOH (up to 100%) until the onset of volcano desorption; without MeSH, both desorb at their respective pure desorption temperatures and also codesorb with water. Compared to MeOH, MeSH binds less well to water, explaining why MeSH escapes during water ice crystallization rather than codesorbing with water. These results show that the larger relative size of MeSH compared to MeOH significantly impacts its ability to bind to water and its entrapment efficiency. Therefore, molecular size plays an important role in the adsorption and retention of S-bearing organics and, in turn, other volatiles in ices.

Keywords: Laboratory astrophysics, Complex organic molecules, Astrochemistry
A Unified, Physical Framework for Mean Motion Resonances. The traditional approach to analyzing mean motion resonances (MMRs) is through the canonical perturbation theory. While this is a powerful method, its generality leads to complicated combinations of variables that are challenging to interpret and require looking up numerical coefficients particular to every different resonance. In this paper, we develop simpler scaling relations in the limit where orbits are closely spaced (period ratios ≲2), and interplanetary interactions can be approximated by only considering the close approaches each time the inner planet overtakes the outer at the conjunction. We develop geometric arguments for several powerful results: (i) that p:p ‑ q MMRs of the same order q are all rescaled versions of one another, (ii) that the general case of two massive planets on closely spaced, eccentric, coplanar orbits can be approximately mapped onto the much simpler case of an eccentric test particle perturbed by a massive planet on a coplanar circular orbit, and (iii) that, while the effects of consecutive conjunctions add up coherently for first-order (p:p ‑ 1) MMRs, they partially cancel for p:p ‑ q MMRs with order q &gt; 1, providing a physical explanation for why these higher-order MMRs are weaker and can often be ignored. Finally, we provide simple expressions for the widths of MMRs and their associated oscillation frequencies that are universal to all closely spaced MMRs of a given order q, in the pendulum approximation.

Keywords: Orbital resonances, Orbital evolution, Celestial mechanics, Three-body problem, Perturbation methods
The Role of Pressure in the Structure and Stability of GMCs in the Andromeda Galaxy. We revisit the role of pressure in the structure, stability, and confinement of Giant Molecular Clouds (GMCs) in light of recently published observations and analysis of the GMCs in the Andromeda galaxy (M31). That analysis showed that, in the absence of any external pressure, most GMCs (57% by number) in M31 would be gravitationally unbound. Here, after a more detailed examination of the global measurements of surface densities and velocity dispersions, we find that GMCs in M31, when they can be traced to near their outermost molecular boundaries, require external pressures for confinement that are consistent with estimates for the mid-plane pressure of this galaxy. We introduce and apply a novel methodology to measure the radial profile of internal pressure within any GMC that is spatially resolved by the CO observations. We show that, for the best-resolved examples in M31, the internal pressures increase steeply with surface density in a power-law fashion with pint ∼ Σ2. At high surface densities, many of these extragalactic GMC profiles break from the single power-law and exhibit upward curvature. Both these characteristics of the variation of internal pressure with surface density are in agreement with theoretical expectations for hydrostatic equilibrium at each radial surface of a GMC, including the outermost boundary.

Keywords: Giant molecular clouds, Andromeda Galaxy
An Investigation of Disk Thickness in M51 from Hα, Paα, and Mid-infrared Power Spectra. Power spectra (PS) of high-resolution images of M51 (NGC 5194) taken with the Hubble Space Telescope and the James Webb Space Telescope (JWST) have been examined for evidence of disk thickness in the form of a change in slope between large scales, which map two-dimensional correlated structures, and small scales, which map three-dimensional correlated structures. Such a slope change is observed here in Hα, and possibly Paα, using average PS of azimuthal intensity scans that avoid bright peaks. The physical scale of the slope change occurs at ∼120 pc and ∼170 pc for these two transitions, respectively. A radial dependence in the shape of the Hα PS also suggests that the length scale drops from ∼180 pc at 5 kpc, to ∼90 pc at 2 kpc, to ∼25 pc in the central ∼kpc. We interpret these lengths as comparable to the thicknesses of the star-forming disk traced by H II regions. The corresponding emission measure is ∼100 times larger than what is expected from the diffuse ionized gas. The PS of JWST Mid-IR Instrument images in eight passbands have more gradual changes in slope, making it difficult to determine a specific value of the thickness for this emission.

Keywords: Interstellar emissions, Interstellar dynamics, Spiral galaxies
Multimessenger Signatures of a Deformed Magnetar in Gamma-Ray Bursts. We study the evolution of a newly formed magnetized neutron star (NS) as a power source of gamma-ray bursts (GRBs) in the light of both gravitational-wave (GW) and electromagnetic (EM) radiation. The compressible and incompressible fluids are employed in order to model the secular evolution of stable Maclaurin spheroids. It is shown that the GW and EM emissions evolve as a function of eccentricity and rotational frequency with time. We find that the luminosity characteristics crucially depend on NS parameters such as magnitude and structure of magnetic field, ellipticity, and the equation of state (EoS) of the fluid. The presence of X-ray flares, whose origins are not yet well understood, can be captured in our model regarding some specific nuclear EoSs. Our model allows us to explain flares that occur within the wide range of 10–104 s and the peak EM luminosity in the order of 1046–1051erg s‑1 by using a reasonable set of parameters, such as magnetic field strength around 1014–1016 G and the quadrupole-to-dipole ratio of magnetic field up to 500. By applying our model to a sample of GRB X-ray flares observed by the Swift/X-ray Telescope, we try to constraint the crucial parameters of a deformed magnetar via a Markov Chain Monte Carlo fitting method. Our analysis shows that ongoing and upcoming joint multimessenger detections can be used to understand the nature of a GRB's central engine and its evolution at the early times of the burst formation.

Keywords: Neutron stars, Gamma-ray bursts, High energy astrophysics, Gravitational waves, Magnetars
The SOFIA Massive (SOMA) Star Formation Survey. V. Clustered Protostars. We present ∼8–40 μm SOFIA-FORCAST images of seven regions of "clustered" star formation as part of the SOFIA Massive Star Formation Survey. We identify a total of 34 protostar candidates and build their spectral energy distributions (SEDs). We fit these SEDs with a grid of radiative transfer models based on the turbulent core accretion (TCA) theory to derive key protostellar properties, including initial core mass, Mc, clump environment mass surface density, Σcl, and current protostellar mass, m*. We also carry out empirical graybody (GB) estimation of Σcl, which allows a case of restricted SED fitting within the TCA model grid. We also release version 2.0 of the open-source Python package sedcreator, which is designed to automate the aperture photometry and SED building and fitting process for sources in clustered environments, where flux contamination from close neighbors typically complicates the process. Using these updated methods, SED fitting yields values of Mc ∼ 30–200 M⊙, Σcl,SED ∼ 0.1–3 g cm‑2, and m* ∼ 4–50 M⊙. The GB fitting yields smaller values of Σcl,GB ≲ 1 g cm‑2. From these results, we do not find evidence for a critical Σcl needed to form massive (≳8 M⊙) stars. However, we do find tentative evidence for a dearth of the most massive (m* ≳ 30 M⊙) protostars in the clustered regions, suggesting a potential impact of environment on the stellar initial mass function.

Keywords: Massive stars, Star formation, Spectral energy distribution, Infrared sources, Interstellar medium, Protostars
On the Origin of Spectral Features Observed during Thermonuclear X-Ray Bursts and in the Aftermath Emission of a Long Burst from 4U 1820–30. We study 15 thermonuclear X-ray bursts from 4U 1820–30 observed with the Neutron Star Interior Composition Explorer (NICER). We find evidence of a narrow emission line at 1.0 keV and three absorption lines at 1.7, 3.0, and 3.75 keV, primarily around the photospheric radius expansion phase of most bursts. The 1.0 keV emission line remains constant, while the absorption features, attributed to wind-ejected species, are stable but show slight energy shifts, likely due to combined effects of Doppler and gravitational redshifts. We also examine with NICER the "aftermath" of a long X-ray burst (a candidate superburst observed by MAXI) on 2021 August 23 and 24. The aftermath emission recovers within half a day from a flux depression. During this recovery phase, we detect two emission lines at 0.7 and 1 keV, along with three absorption lines whose energies decrease to 1.57, 2.64, and 3.64 keV. Given the nature of the helium white dwarf companion, these absorption lines during the aftermath may originate from an accretion flow, but only if the accretion environment is significantly contaminated by nuclear ashes from the superburst. This provides evidence of temporary metal enhancement in the accreted material due to strong wind loss. Moreover, we suggest that the absorption features observed during the short X-ray bursts and in the superburst aftermath share a common origin in heavy nuclear ashes enriched with elements like Si, Ar, Ca, or Ti, either from the burst wind or from an accretion flow contaminated by the burst wind.

Keywords: Accretion, Low-mass x-ray binary stars, X-ray binary stars, X-ray bursts
Characterizing Chromospheric Condensation with High-cadence Si IV Observations from IRIS. Chromospheric flare ribbons are believed to result from coronal magnetic energy released by reconnection and propagating down to the cooler, lower atmosphere. They offer an opportunity to study flare reconnection using chromospheric observations at a spatial and temporal resolution higher than typically available by direct coronal observation. Transient downflows, known as chromospheric condensations (CCs), often occur at the leading edge of a ribbon as a prompt response to the energy input. These have properties that have recently been shown to relate to the coronal energy release process driving them. We use a set of IRIS observations of flare ribbons, made at high cadence in the sit-and-stare mode, to identify and analyze a sample of 134 CC episodes. Among this sample, 132 episodes have at least one time frame that exhibited a double-Gaussian profile. Clear CC appears to occur in only about one fifth of all ribbon pixels, indicating that flare energy release is necessary but not sufficient for producing the characteristic form of CC. We find that condensation pixels form clusters averaging 1 arcsec in extent, all undergoing similar and concurrent time evolution. This suggests that coronal reconnection and associated energy release occur in localized patches whose spatial extent maps to around 1 arcsec in the chromosphere.

Keywords: Solar flares, Solar ultraviolet emission
SMILES: Potentially Higher Ionizing Photon Production Efficiency in Overdense Regions. The topology of reionization and the environments where galaxies efficiently produce ionizing photons are key open questions. For the first time, we investigate the trend between ionizing photon production efficiency, ξion, and galaxy overdensity,  log(1+δ) . We analyze the ionizing properties of 79 galaxies between 1.0 &lt; z &lt; 5.2 using JWST NIRSpec medium-resolution spectra from the Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES) program. Among these, 67 galaxies have Hα coverage, spanning 1.0 &lt; z &lt; 3.1. The galaxy overdensity,  log(1+δ) , is measured using the JADES photometric catalog, which covers the SMILES footprint. For the subset with Hα coverage, we find that  logξion  is positively correlated with  log(1+δ) , with a slope of  0.94−0.46+0.46 . Additionally, the mean ξion for galaxies in overdense regions ( log(1+δ)&gt;0.1 ) is 2.43 times that of galaxies in lower density regions ( log(1+δ)&lt;0.1 ). This strong trend is found to be independent of redshift evolution. Furthermore, our results confirm the robust correlations between ξion and the rest-frame equivalent widths of the [O III] or Hα emission lines. Our results suggest that galaxies in high-density regions are efficient producers of ionizing photons.

Keywords: Reionization, High-redshift galaxies
Using Machine Learning Method for Variable Star Classification Using the TESS Sectors 1–57 Data. The Transiting Exoplanet Survey Satellite is a wide-field all-sky survey mission designed to detect Earth-sized exoplanets. After over 4 yr of photometric surveys, data from sectors 1–57, including approximately 1,050,000 light curves with a 2 minute cadence, were collected. By crossmatching the data with Gaia's variable star catalogue, we obtained labeled data sets for further analysis. Using a random forest classifier, we performed classification of variable stars and designed distinct classification processes for each subclass: 6770 EA, 2971 EW, 980 CEP, 8347 DSCT, 457 RRab, 404 RRc, and 12,348 ROT were identified. Each variable star was visually inspected to ensure the reliability and accuracy of the compiled catalog. Subsequently, we ultimately obtained 6046 EA, 3859 EW, 2058 CEP, 8434 DSCT, 482 RRab, 416 RRc, and 9694 ROT, and a total of 14,092 new variable stars were discovered.

Keywords: Surveys, Catalogs, Astronomy data analysis, Variable stars
A Thorough Exploration of the Metal-rich Massive Open Cluster NGC 6253: Focusing on Membership, Binaries, Stragglers, and Mass Function. This study provides an in-depth analysis of the ancient open galactic cluster NGC 6253, characterized by the presence of both blue and yellow straggler stars. Utilizing a hybrid approach that integrates DBSCAN and Gaussian mixture models with GAIA Data Release 3, we effectively identified the cluster members, discovering 11 blue and 7 yellow stragglers. The structure of the cluster considerably exceeds its tidal radius, which implies that there is an evident tidal tail structure. A calculated relaxation time of 32.469 Myr, which is considerably shorter than its 3.5 Gyr age, indicates that NGC 6253 has attained dynamic relaxation. The mass segregation timescale observed for most stars in our sample is brief compared to the cluster's age, offering strong evidence of mass segregation. Orbital integration using the MWPotential2014 model and analysis of binary members further corroborate our results. The birth radius of 6.78 kpc suggests formation within the solar circle. Our research into the present mass function reveals a top-heavy distribution common to both single and binary star populations. Additionally, our analysis shows that among binary systems, more massive binaries are more centrally located compared to their less massive counterparts, underscoring the significant role of binary stars in shaping the cluster's overall mass distribution.

Keywords: Open star clusters
Model-agnostic Cosmological Inference with SDSS-IV eBOSS: Simultaneous Probing for the Background and Perturbed Universe. Here, we explore certain subtle features imprinted in data from the completed Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) as a combined probe for the background and perturbed universe. We reconstruct the baryon acoustic oscillation and redshift space distortion observables as functions of redshift, using measurements from SDSS alone. We apply the multi-task Gaussian process framework to model the interdependencies of cosmological observables DM(z)/rd, DH(z)/rd, and fσ8(z), and track their evolution across different redshifts. Subsequently, we obtain a constrained three-dimensional phase space containing DM(z)/rd, DH(z)/rd, and fσ8(z) at different redshifts probed by the SDSS-IV eBOSS survey. Furthermore, assuming the Λ-cold dark matter (ΛCDM) model, we obtain constraints on model parameters Ωm, H0rd, σ8, and S8 at each redshift probed by SDSS-IV eBOSS. This indicates redshift-dependent trends in H0, Ωm, σ8, and S8 in the ΛCDM model, suggesting a possible inconsistency in the ΛCDM model. Ours is a template for model-independent extraction of information for both a background and perturbed universe using a single galaxy survey, taking into account all the existing correlations between background and perturbed observables and this can be easily extended to future DESI-3YR as well as Euclid results.

Keywords: Cosmology, Cosmological parameters, Gaussian Processes regression, Baryon acoustic oscillations, Dark energy
Systematic Search for Blue Hypervelocity Stars from LAMOST Survey. Hypervelocity stars (HVSs) represent a unique class of objects capable of escaping the gravitational pull of the Milky Way due to extreme acceleration events, such as close encounters with the supermassive black hole at the Galactic center (GC), supernova explosions in binary systems, or multibody dynamical interactions. Finding and studying HVSs are crucial to exploring these ejection mechanisms, characterizing central black holes, probing the GC environment, and revealing the distribution of dark matter in our Galaxy. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic surveys have so far identified four B-type unbound HVSs. To expand this sample with the second-phase LAMOST survey that started in 2018, we conducted a systematic search for early-type HVSs using the LAMOST Data Release 10. We identified 125 early-type high-velocity candidates with total velocities exceeding 300 km s‑1. Among them, we report 10 new unbound B- and A-type HVS candidates (designated LAMOST-HVS 5 through LAMOST-HVS 14), tripling the number of unbound HVSs previously identified by LAMOST. Kinematic analyses suggest that these newly discovered HVS candidates likely originated either from the GC or via dynamical interactions. Future high-resolution follow-up observations promise to refine the stellar parameters, distances, and elemental abundances of these candidates, thereby providing deeper insights into their origins and broadening their potential applications across astrophysics.

Keywords: Early-type stars, Hypervelocity stars, Sky surveys, Radial velocity