Sazuna/UAT_keywords huggingface dataset:
A Shock Crashing into Confined Dense Circumstellar Matter Brightens the Nascent SN 2023ixf. Red supergiants may experience a short-lived period of episodic mass loss rather than steady winds before their core collapses, leading to dense circumstellar matter (CSM) close to core-collapse supernovae (SNe). Interaction of SN ejecta with such nearby CSM can generate additional radiation, appending to the cooling radiation from the shock breakout of the progenitor envelope, to brighten the nascent SN explosion. This phenomenon is conspicuous for SN 2023ixf as its V-band brightness showed a rapid increase of about three magnitudes from the first to the third day after the time of the first light, which is distinctive among type II SNe with flash ionized signatures. In this paper, we employed a Monte Carlo method to simulate the radiative diffusion process in the unshocked CSM. Considering a wide range of mass-loss rates from 10‑5 to 10‑2 M⊙ yr‑1, we confirmed that the fast-rising light curve of SN 2023ixf can be fitted by the interaction of the SN ejecta with a CSM having a mass-loss rate of about 10‑2 M⊙ yr‑1 located within 1015 cm of the progenitor.

Keywords: Circumstellar matter, Light curves, Supernovae, Core-collapse supernovae
Are Multiwavelength Variability Events in Blazars Driven by a Common Stochastic Process?. We investigate the underlying stochastic processes driving the multiwavelength variability of the blazar BL Lacertae over the past two decades. Observations from Weihai Observatory over 224 nights reveal that the power spectral slopes of intra-night variability follow a Gaussian distribution, ranging from approximately 0.4–2.6, with an average trend consistent with the long-term variability power spectrum. Using power spectral analysis methods, such as the classical periodogram and the Lomb–Scargle periodogram, in combination with modeling techniques such as the power spectral response method, the multiple fragment variance function, and the continuous time autoregressive moving average, we study the multiband power spectral characteristics across a wide range of timescales (∼7 dex). The results demonstrate that, at lower frequencies, the power spectral density across different bands shows remarkable consistency, suggesting that these variations may be driven by a common stochastic process related to the accretion disk. However, significant discrepancies arise at higher frequencies, indicating the presence of multiple stochastic processes. We propose that the variability is governed by at least two distinct processes: one related to disk stochastic processes, dominating the long-term variability, and another associated with jet stochastic processes, which may result from turbulence, particle acceleration, and shock interactions within the jet, and drive the short-term, high-frequency variations. These findings provide unique insights into the complex mechanisms underlying blazar variability and suggest an intrinsic connection between the accretion disk and jet dynamics.

Keywords: Blazars, Non-thermal radiation sources, BL Lacertae objects, Relativistic jets
Dense Cores in IRDC G14.225-0.506 Revealed by ALMA Observations. Dense cores in massive, parsec-scale molecular clumps are sites that harbor protocluster formation. We present results from observations toward a hub–filament structure of a massive infrared (IR) dark cloud G14.225-0.506 using the Atacama Large Millimeter/submillimeter Array. The dense cores are revealed by the 1.3 mm dust continuum emission at an angular resolution of ∼1 5 and are identified through the hierarchical dendrogram technique. Combining with the N2D+ 3–2 spectral line emission and gas temperatures derived from a previous NH3 study, we analyze the thermodynamic properties of the dense cores. The results show transonic and supersonic-dominated turbulent motions. There is an inverse correlation between the virial parameter and the column density, which implies that denser regions may undergo stronger gravitational collapse. Molecular outflows are identified in the CO 2–1 and SiO 5–4 emission, indicating active protostellar activities in some cores. Besides these star formation signatures revealed by molecular outflows in the dense cores, previous studies in the IR, X-ray, and radio wavelengths also found a rich and widespread population of young stellar objects, showing active star formation both inside and outside of the dense cloud.

Keywords: Star forming regions, Star formation, Infrared dark clouds
Fundamental Understanding of Magnetic Reconnection via Spiral CT Scan. II. Ion-velocity Pattern and Electron-velocity Pattern. For the first time, we reveal the ion-velocity pattern and electron-velocity pattern around a reconnection X-line by using the spiral CT scan technique, which is a novel technique analogous to that in the hospital. This X-line was detected by the MMS spacecraft and has been widely believed to host a non-guide-field reconnection. With the help of such an advanced technique, we find two interesting features of ion velocities: (1) in the reconnection plane, ion velocities are diverged to form a "saddle-shape" pattern surrounding the X-point at scale above 0.5 di (ion inertial length), but are stochastic near the X-point at scale below 0.5 di; (2) in the out-of-plane direction, ion velocities are large in the magnetosphere, but are small in the magnetosheath. Also, we successfully identify six features of electron velocities: (1) out-of-plane electron jet with scale of 0.1 di near the X-point, (2) coupled electron and ion velocities at &gt;0.8 di but decoupling of them at &lt;0.8 di, (3) weak electron inflow and strong electron outflow at 0.1 di &lt; Δ &lt; 0.8 di, (4) stochastic electron velocities at &lt;0.1 di, (5) intense electron stream at 0.1 di &lt; Δ &lt; 0.8 di at the separatrix, and (6) field-aligned electron beam in the inflow region. Among these features, the first seven greatly meet theoretical expectations if we define the ion diffusion region as Δ &lt; 0.8 di and electron diffusion region as Δ &lt; 0.1 di; the last one is a surprise, indicating that only part of the electrons participate in the reconnection process around the X-line.

Keywords: Space plasmas, Solar magnetic reconnection, Plasma physics
Radial Flow Component of Sun's High-frequency Retrograde Inertial Waves. Solar inertial modes have the potential to surpass the diagnostic capabilities of acoustic waves in probing the deep interior of the Sun. The fulfillment of this potential requires an accurate identification and characterization of these modes. Among the set of detected inertial modes, the equatorially antisymmetric "high-frequency retrograde" (HFR) modes has attracted special interest because numerical studies have suggested that they are not purely toroidal, as initial observations suggested, and predicted that they would possess a significant radial flow signal at depth. Here, we analyze ∼13 yr of Helioseismic and Magnetic Imager/Solar Dynamics Observatory 5° ring tiles and discover a horizontal-divergence signal, directly connected to radial flows, in the near-surface layers of the Sun. We demonstrate that this signal is indeed part of the HFR modes and not spatial leakage from prograde flows associated with magnetic regions. The amplitudes of the horizontal divergence are approximately half that associated with radial vorticity. We also report the presence of a ridge of enhanced power, although with a signal-to-noise ratio of 0.3, in the retrograde frequencies that coincides with the HFR latitudinal overtones reported by models. Using numerical linear models, we find reasonable agreement with observations, though future work on boundary considerations and the inclusion of the near-surface may improve future inferences. This is the first instance where numerical studies of solar inertial modes have guided observations, giving further confidence to past inferences that rely upon numerical models.

Keywords: Solar oscillations, Internal waves, Solar physics, Solar interior
A Spatiotemporal Data Cube Approach to Classification of Variable Stars: A Catalog of Candidate Variable Stars from the TESS Full-frame Image Raw Data. We present a novel technique to identify variable stars in large surveys that performs classification not on the 1D light curves but on the spatiotemporal data cube. Such an approach can allow the model to better discriminate against the systematics in the background flux and consider the variability across the entire point-spread function, which can be advantageous to large surveys such as Transiting Exoplanet Survey Satellite (TESS). We perform a search for eclipsing, pulsating, and rotating variables in TESS full-frame images. This classification was done using a neural network that has been trained on variable stars identified in other surveys. In total we identify 3.1 million candidate variable sources. Although these sources should undergo significant vetting to confirm them using more traditional techniques, through assembling the catalog of the most promising candidates, it should be possible to significantly narrow down the list of light curves of sources that would need to be constructed for such an analysis. With an increasing number of surveys aiming to do photometric monitoring coming online in the future (e.g., LSST), a similar analysis with an improved training set could be advantageous in classifying variable stars.

Keywords: Catalogs, Convolutional neural networks, Variable stars
Comparative Analysis of Hall Effect Implementations in Hall Magnetohydrodynamics. There is no standard numerical implementation of the Hall effect, which is one of the nonideal magnetohydrodynamic (MHD) effects. Numerical instability arises when a simple implementation is used, in which the Hall electric field is added to the electric field to update magnetic fields without further modifications to the numerical scheme. In this paper, several implementations proposed in the literature are compared to identify an approach that provides stable and accurate results. We consider two types of implementations of the Hall effect. One is a modified version of the Harten─Lax─van Leer method (HALL-HLL), in which the phase speeds of whistler waves are adopted as the signal speeds; the other involves adding a fourth-order hyper-resistivity to a Hall-MHD code. Based on an extensive series of test calculations, we find that hyper-resistivity yields more accurate results than HALL-HLL, particularly in problems where the whistler wave timescale is shorter than the timescales of the physical processes of interest. Through both von Neumann stability analysis and numerical experiments, an appropriate coefficient for the hyper-resistivity is determined.

Keywords: Computational methods, Magnetic fields, Magnetohydrodynamical simulations
Methods for Tracking Cosmic-Ray Spectral Changes Using Neutron Monitors at High Cutoff Rigidity. Neutron monitors are a standard tool for high-precision monitoring of changes in the Galactic cosmic ray (GCR) flux that occur as a result of variations of the heliospheric conditions and solar storms. In Thailand, we have developed a mobile neutron monitor named "Changvan" based on the 3NM64 design, except that the middle counter lacks lead producer rings, so we call it a semileaded neutron monitor. From 2021 April to 2023 April, the Changvan operated at the Science and Technology Park, Mae Hia, Chiang Mai, Thailand, at an altitude of about 340 m above sea level, with a vertical cutoff rigidity of 16.7 GV, which is near the highest value observed globally. With a similar cutoff rigidity, the nearby Princess Sirindhorn Neutron Monitor is an 18NM64 at the summit of Doi Inthanon, the highest mountain in Thailand, at 2560 m above sea level. We examine how count rates at different altitudes with similar cutoffs, count rates from the unleaded versus leaded counters, and the leader fraction measured from time-delay histograms all reflect GCR spectral differences, thus providing a variety of techniques for tracking cosmic-ray spectral changes. Applied at high cutoff rigidity, these methods extend the reach of the worldwide neutron monitor network to even higher rigidity.

Keywords: Galactic cosmic rays, Space weather, Cosmic ray detectors, Solar-terrestrial interactions
Unveiling Bifurcated Blue Straggler Sequences in NGC 2173: Insights from Binary Evolution. Identifying bifurcated blue straggler (BS) sequences in color–magnitude diagrams (CMDs) of star clusters has long been regarded as a powerful diagnostic for distinguishing different BS formation mechanisms. While such bifurcations are typically associated with core-collapsed clusters, their detection in dynamically young clusters raises new questions about their origins. In this study, using high-precision proper motion data derived from Hubble Space Telescope multiepoch observations, we confirm the existence of two distinct BS sequences in the Large Magellanic Cloud cluster NGC 2173 (∼1.58 Gyr): a well-defined, narrow blue sequence and a sparser red sequence. The extended core region excludes collisional formation as a viable channel for BS formation. Our binary evolution models suggest that nonconservative mass transfer (MT) is essential for shaping the distribution of BS binaries in the CMD. The red sequence primarily comprises BS binaries formed through conservative ongoing MT. In contrast, the blue sequence BS binaries are formed through nonconservative post-MT processes, all involving white dwarf (WD) companions. These BS+WD binary systems may subsequently undergo a second MT phase, leading to the formation of double WD systems.

Keywords: Blue straggler stars, Star clusters
The Impact of Accretion on FRB Radiation Mechanisms in Binary Systems: Constraints and Implications. Fast radio bursts (FRBs) are intense, millisecond-duration radio transients that have recently been proposed to arise from coherent radiation mechanisms within the magnetosphere of neutron stars. Observations of repeating FRBs, including periodic activity and large variations in Faraday rotation measures, suggest that these bursts may have binary system origins, with a massive companion. In this work, we investigate how accretion from a massive companion influences the FRB radiation within the magnetosphere of the neutron star. Focusing on two widely accepted pulsar-like coherent radiation mechanisms, we establish the parameter space for neutron stars that allows FRB generation, even in the presence of accreted matter. Our analysis shows that coherent curvature radiation is only viable within a narrow range of parameters, while the magnetic reconnection mechanism operates across a broader range. In both cases, the neutron star must possess a strong magnetic field with strength ≳1013 G. These findings at least indicate that the central engines responsible for producing observable FRBs in binary systems are indeed magnetars.

Keywords: Magnetars, Radio transient sources
An NGC 1068-informed Understanding of Neutrino Emission of the Active Galactic Nucleus TXS 0506+056. We present arguments that the neutrinos observed by IceCube from the active galactic nucleus TXS 0506+056 may originate near its core and not in the blazar jet. The origin of the neutrinos is consistent with the mechanism that produces the neutrino flux observed from the active galaxies NGC 1068 and NGC 4151, but requires an Eddington luminosity cosmic-ray flux to compensate for its larger distance. Like NGC 1068, the source is characterized by episodes of high X-ray emission and is gamma-ray-obscured during the 2014 burst, and there is evidence that this is also the case during the short burst in 2017 that produced IC-170922. The observations may be explained as a flux originating in an obscured core within 10 ∼ 100 Schwarzschild radii from the central black hole, which is not transparent to gamma rays from the decay of neutral pions accompanying the neutrinos.

Keywords: Black hole physics, Black holes, High energy astrophysics, Blazars, Neutrino astronomy, Seyfert galaxies, Active galactic nuclei, X-ray sources, Gamma-rays, Particle astrophysics, Cosmic rays
Prospects for Detecting Cosmic Filaments in Lyα Emission across Redshifts z = 2─5. The standard ΛCDM cosmological model predicts that a large amount of diffuse neutral hydrogen distributes in cosmic filaments, which could be mapped through Lyα emission observations. We use the hydrodynamical simulation Illustris-TNG50 to investigate the evolution of surface brightness (SB) and detectability of neutral hydrogen in cosmic filaments across redshifts z = 2─5. While the H I column density of cosmic filaments decreases with redshift, due to the rising temperature with cosmic time in filaments, the SB of Lyα emission in filaments is brighter at lower redshifts, suggesting that the detection of cosmic filaments is more feasible at lower redshifts. However, most of the Lyα emission from cosmic filaments is around 10−21 , making it extremely challenging to detect with current observational instruments. We further generate mock images using the Multi-Unit Spectroscopic Explorer (MUSE) spectrograph installed on the Very Large Telescope (VLT) and a MUSE-like spectrograph on the upcoming Extremely Large Telescope (ELT). Our finding indicates that while the VLT can only detect filamentary structures made of dense gas in galactic centers, the ELT is expected to reveal much finer filamentary structures from diffuse neutral hydrogen outside of galaxies. Compared to the VLT, both the number density and the longest length of filaments are greatly boosted with the ELT. Hence the forthcoming ELT is highly promising to provide a clearer view of cosmic filaments in Lyα emission.

Keywords: Diffuse radiation, Hydrodynamical simulations, Cosmic web, Intergalactic filaments
The Impact of the Galactic Bar and the Large Magellanic Cloud on Hypervelocity Star Trajectories. Hypervelocity stars (HVSs) ejected from the Galactic center at speeds faster than the Galactic escape velocity are useful tools to provide insight into the Milky Way's dark matter halo. However, most characterizations of HVS orbits assume static models of the Milky Way's gravitational potential. In this work, we assess the influence of the Galactic bar and the Large Magellanic Cloud (LMC) on HVS trajectories, comparing them with those from an axisymmetric potential. We simulate 28,000 HVSs ejected over the last 100 Myr and find that ignoring the bar and LMC can cause their apparent ejection location to drift by up to 100 pc. Applying two standard HVS potential fitting methods to our sample shows that they are unable to perform as designed when nonaxisymmetric effects are neglected. We calculate the angle between HVS Galactocentric position and velocity, and find the LMC and bar can induce a deflection angle of up to several degrees. Using mock Gaia Data Release 4 observations, however, we show that this deflection is too small in magnitude to be measured in the near future without significantly improved observational uncertainties, particularly in heliocentric distance. Our results emphasize the need to account for the bar and LMC in modeling the Galactic potential using HVSs as a tracer.

Keywords: Milky Way dark matter halo, Supermassive black holes, Galactic center, Hypervelocity stars, Large Magellanic Cloud, Galactic bar
HST Grism Observations of a z ∼ 1.8 Cluster Candidate from the Clusters Occupied by Bent Radio AGN (COBRA) Survey. We present new Hubble Space Telescope/Wide Field Camera 3 G141 grism observations for COBRA 1411+3415, originally identified as a high-redshift cluster candidate in the Clusters Occupied by Bent Radio AGN (COBRA) survey using radio, infrared, and optical data. We spectroscopically identify seven cluster members within a 0.5 Mpc radius with grism redshifts in the range 1.8006 ≤ zgrism ≤ 1.8175, consistent with COBRA 1411+3415 being a high-redshift cluster with a mean redshift of &lt;zgrism&gt; = 1.8106 ± 0.0006. The detection of seven galaxies within this small redshift range is significant above the background distribution of galaxies at the level of 5σ. The line-of-sight velocity dispersion of the cluster is found to be σ∥ =   km s‑1 with a virial mass of M200 ≈   × 1014 M⊙. However, the mass may be lower if the cluster is still in formation. In projected phase space, we also identify two possible infalling members of COBRA 1411+3415 and two additional structures at z ∼ 1.73 and z ∼ 1.88. The similar spatial distributions and small projected separation from the main cluster suggest they could be a part of the same large-scale filament and together may form a protocluster system that could eventually merge to form a single, massive cluster. COBRA 1411+3415 is the highest-redshift cluster to be spectroscopically confirmed using a bent, double-lobed radio source as a cluster tracer.

Keywords: Infrared spectroscopy, Galaxy environments, High-redshift galaxy clusters, Active galactic nuclei, Galaxy spectroscopy, High-redshift galaxies
Gaia Net: Toward Robust Spectroscopic Parameters of Stars of all Evolutionary Stages. We present a new processing of XP spectra for 220 million stars released in Gaia DR3. The new data model is capable of handling objects with Teff between 2000 and 50,000 K and with   between 0 and 10, including objects of multitude of masses and evolutionary stages. This includes for the first time ever robust processing of spectroscopic parameters for pre-main-sequence stars, with   sensitivity toward their age. Through this analysis we examine the distribution of young low-mass stars with ages of up to 20 Myr in the solar neighborhood, and we identify a new massive (&gt;1000 stars) population, Ophion, which is found east of Sco─Cen. This population appears to be fully disrupted, with negligible kinematic coherence. Nonetheless, due its young age it appears to still persist as a spatial overdensity. Through improved determination of ages of the nearby stars, it may be possible to better recover the star-forming history of the solar neighborhood outside of the moving groups.

Keywords: Stellar populations, Surface gravity, Stellar properties, Spectroscopy
Dark Matter Genesis. Recent discoveries of primordial black hole (PBH) candidates by means of high-cadence microlensing open the way to a physical understanding of the formation of dark matter as a chapter in the thermal history of the Universe. Two complementary sites of PBH formation are considered, inflation and the early Universe at TeV to MeV energies. In the latter case the Friedmann equation, together with mass measurements, reveal the threshold energy, the mass spectrum, and the likely end point of this epoch. Some of the many recent exoplanet detections may conceivably have been detections of PBHs. When the Universe cools to MeV temperatures, larger-mass PBHs would form similarly, reaching the supermassive regime. The discovery of numerous supermassive black holes at high redshift with JWST fulfils this expectation. We corroborate the idea that Planck mass relics could be an important component of dark matter, and find that these are formed by PBHs with initial mass less than approximately 6 × 10‑16 M⊙ and cosmic temperature above 109 GeV. Although in some mass ranges PBHs can only make up a modest fraction of Ωm, it is possible that all astrophysical dark matter, as distinct from axions and weakly interacting massive particles, is of PBH origin.

Keywords: Cosmology, Supermassive black holes, Gravitational microlensing exoplanet detection, Inflationary universe, Primordial black holes