Sazuna/UAT_keywords huggingface dataset:
Two Intermittent Eruptions of a Minifilament Triggered by a Two-step Magnetic Reconnection Within a Fan-spine Configuration. Although numerous works have concentrated on minifilament eruption in complex configurations, the detailed triggering mechanism is still an open question. Using the observational data from the New Vacuum Solar Telescope and Solar Dynamics Observatory, we studied a two-step magnetic reconnection process that triggered a minifilament that erupted intermittently within a fan-spine structure in the active region NOAA 13272. The first-step reconnection occurred between a set of low-lying small-scale magnetic loops and their nearby inner spine, resulting in the appearance of a brightening at the reconnection site and the reconfiguration of the inner spine. As the reconfigured inner spine approached the outer spine, reconnection occurred between them at the null point and led to the minifilament erupting partially. Subsequently, this two-step reconnection scenario occurred again and triggered the minifilament to erupt completely. The null point reconnection was supported by the changes in the topological structure of the inner spine and the outer spine, circular ribbon flares, remote brightenings, and the brightening of the outer spine. The null point reconnection related to the second eruption was also confirmed by some plasmoids expelled from the reconnection site. Further, the results of the magnetic field extrapolation reveal the existence of a fan-spine structure involving a three-dimensional null point. We suggest that the two-step reconnection triggers the two eruptions, in which the null point reconnection plays a direct role, but the dynamical evolution of the inner spine and the outer spine driven by the first-step reconnection might be a precursor of the subsequent null point reconnection.

Keywords: Solar active regions, Solar filaments, Solar magnetic reconnection
Simulating Radio Synchrotron Morphology, Spectra, and Polarization of Cosmic Ray Driven Galactic Winds. The formation of galaxies is significantly influenced by galactic winds, possibly driven by cosmic rays due to their long cooling times and better coupling to plasma compared to radiation. In this study, we compare the radio observations of the edge-on galaxy NGC 4217 from the CHANG-ES collaboration catalog with a mock observation of an isolated galaxy based on the AREPO simulation that adopts the state-of-the-art two-moment cosmic ray transport treatment and multiphase interstellar medium model. We find significant agreement between the simulated and observed images and spectroscopic data for reasonable model parameters. Specifically, we find that (i) the shape of the intensity profiles depends weakly on the magnitude of the magnetic field, the distance of the simulated galaxy, and the normalization of the CR electron spectrum. The agreement between the mock and actual observations is degenerate with respect to these factors; (ii) the multiwavelength spectrum above 0.1 GHz is in agreement with the radio observations and its slope is also only weakly sensitive to the magnetic field strength; (iii) the magnetic field direction exhibits X-shaped morphology, often seen in edge-on galaxies, which is consistent with the observations and indicates the presence of a galactic-scale outflow. Our results highlight the importance of incorporating advanced cosmic ray transport models in simulations and provide a deeper understanding of galactic wind dynamics and its impact on galaxy evolution.

Keywords: Galaxy magnetic fields, Radio continuum emission, Non-thermal radiation sources, Cosmic rays
Sharp Periodic Flares and Long-term Variability in the High-mass X-Ray Binary XTE J1829‑098 from RXTE PCA, Swift BAT, and MAXI Observations. XTE J1829‑098 is a transient X-ray pulsar with a period of ∼7.8 s. It is a candidate Be star system, although the evidence for this is not yet definitive. We investigated the twenty-year-long X-ray light curve using the Rossi X-ray Timing Explorer Proportional Counter Array (PCA), Neil Gehrels Swift Observatory Burst Alert Telescope, and the Monitor of All-sky X-ray Image. We find that all three light curves are clearly modulated on the ∼244 days orbital period previously reported from PCA monitoring observations, with outbursts confined to a narrow phase range. The light curves also show that XTE J1829‑098 was in an inactive state between approximately 2008 December and 2018 April, and no strong outbursts occurred. Such behavior is typical of Be X-ray binary systems, with the absence of outbursts likely related to the dissipation of the Be star's decretion disk. The mean outburst shapes can be approximated with a triangular profile and, from a joint fit of this to all three light curves, we refine the orbital period to 243.95 ± 0.04 days. The mean outburst profile does not show any asymmetry and has a total phase duration of 0.140 ± 0.007. However, the PCA light curve shows that there is considerable cycle-to-cycle variability of the individual outbursts. We compare the properties of XTE J1829‑098 with other sources that show short phase-duration outbursts, in particular GS 1843‑02 (2S 1845‑024), which has a very similar orbital period, but longer pulse period, and whose orbit is known to be highly eccentric.

Keywords: Neutron stars, Be stars, High mass x-ray binary stars, Binary stars
Probing the Extended Atmospheres of AGB Stars. I. Synthetic Imaging of 1D Hydrodynamical Models at Radio and (Sub-)millimeter Wavelengths. We investigate the observable characteristics of the extended atmospheres of asymptotic giant branch (AGB) stars across a wide range of radio and (sub-)millimeter wavelengths using state-of-the-art 1D dynamical atmosphere and wind models over one pulsation period. We also study the relationships between the observable features and model properties. We further study practical distance ranges for observable sources assuming the capabilities of current and upcoming observatories. We present time-variable, frequency-dependent profiles of pulsating AGB stars' atmospheres, illustrating observable features in resolved and unresolved observations, including disk brightness temperature, photosphere radius, and resolved and unresolved spectral indices. Notably, temporal variations in disk brightness temperature closely mirror the temperature variability of the stellar atmosphere. We find that while the photospheric radius decreases due to gas dilution in the layers between consecutive shocks, the increase in the observed stellar radius reflects shock propagation through the atmosphere during the expansion phase, providing a direct measurement method for the shock velocity. Furthermore, our models indicate that enhanced gas temperatures after the passage of a strong shock might be observable in the high-frequency Atacama Large Millimeter/submillimeter Array (ALMA) bands as a decrease in the brightness temperature with increasing frequency. We demonstrate that synthetic observations based on state-of-the-art dynamical atmosphere and wind models are necessary for proper interpretations of current (ALMA and Very Large Array (VLA)) and future (Square Kilometre Array and next-generation VLA) observations and that multiwavelength observations of AGB stars are crucial for empirical studies of their extended atmospheres.

Keywords: Radio continuum emission, Asymptotic giant branch stars, Radiative transfer, Stellar atmospheres
The Milky Way Bar Potential Constrained by the Kinematics of SiO Maser Stars in BAaDE Survey. We introduce a novel method that utilizes the longitude–velocity (l ‑ v) envelope to constrain the Milky Way (MW) bar potential. Previous work used the l ‑ v diagram to explain the distribution of the observed high-velocity stars. We successfully reproduce their results but find that their method is limited to only one type of periodic orbits. In contrast, we propose that the l ‑ v envelope provides much more comprehensive constraints. We compare the properties of test particles in the M. Portail et al. MW potential model (P17) with the observed SiO maser stars from the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey. We find that the l ‑ v envelope generated by the bar potential demonstrates reasonable agreement with the observational data, albeit with slight discrepancies near the Galactic center. The inconsistencies suggest that the P17 potential yields a lower central rotation curve, a slightly larger quadrupole strength, or a possibly underestimated pattern speed. We also adopt an updated version of the P17 potential with a modified central mass component proposed by G. H. Hunter et al. (H24). The fitting of the l ‑ v envelope suggests that the H24 potential does not completely address the existing challenges and may hint at a possible underestimation of the central bar mass. Our study demonstrates that the l ‑ v envelope can be used as a valuable tool for constraining the Galactic potential and provides insights into the MW bar potential.

Keywords: Galaxy bulges, Galaxies
PGC 44685: A Dwarf Star-forming Lenticular Galaxy with a Wolf–Rayet Population. Lenticular galaxies (S0s) are formed mainly from the gas stripping of spirals in the cluster. But how S0s form and evolve in the field is still in need of being resolved. Based on spatially resolved observations from the optical Hispanic Astronomical Center in Andalusia 3.5 m telescope with the PPAK Integral Field Spectroscopy instrument and Northern Extended Millimeter Array, we study a dwarf (M * &lt; 109 M ⊙) S0, PGC 44685, with triple star-forming regions in the central region, namely, A, B, and C, respectively. In northwest region C, we clearly detect the spectral features of Wolf–Rayet (W-R) stars and quantify the W-R population by stacking spectra with high W-R significance. Most of the molecular gas is concentrated in region C(W-R), and there is diffuse gas around regions A and B. The W-R region possesses the strongest intensities of Hα, CO(1–0), and 3 mm continuum, indicating its ongoing violent star formation (gas depletion timescale ≲25 Myr) with tentative hundreds (&lt;500) km s‑1 of stellar winds accompanied by the W-R phase. Most (∼96%) of the three star-forming regions show relatively low-metallicity distributions, suggesting possible (minor) accretions of metal-poor gas that trigger the subsequent complex star formation in a field S0 galaxy. We speculate that PGC 44685 will become quiescent in less than 30 Myr if there is no new molecular gas to provide raw materials for star formation. The existence of this dwarf star-forming S0 presents an example of star formation in the low-mass/metallicity S0 galaxy.

Keywords: Lenticular galaxies, Dwarf galaxies, Star formation, Galaxy evolution, Elliptical galaxies, Galaxies
CME Arrival Time Prediction Based on Coronagraph Observations and Machine-learning Techniques. The timely and precise prediction of the arrival time of coronal mass ejections (CMEs) is crucial in mitigating their potential adverse effects. In this study, we present a novel prediction method utilizing a deep-learning framework coupled with physical characteristics of CMEs and background solar wind. Time series images from synchronized solar white-light and EUV observations of 156 geoeffective CME events during 2000–2020 are collected for this study, according to the Richardson and Cane interplanetary CME directory and the SOHO/LASCO CME catalog of NASA/CDAW. The CME parameters are obtained from the CDAW website and the solar wind parameters are from OMNI2 website. The observational images are first fed into a convolutional neural network (CNN) to train a regression model as Model A. The results generated by the original CNN are then integrated with 11 selected physical parameters in additional neural network layers of Model B to improve the predictions. Under optimal configurations, Model A achieves a minimum mean absolute error (MAE) of 7.87 hr, whereas Model B yields a minimum MAE of 5.12 hr. During model training, we employed tenfold cross validation to reduce the occasionality of biased data. The average MAE of Model B on 10 folds is 33% lower than that of model A. The results demonstrate that combining the imaging observations with the physical properties of CMEs and background solar wind to train a machine-learning model can benefit the forecasting of CME arrival times.

Keywords: Convolutional neural networks, Solar coronal mass ejections
Dynamics of a Galaxy at z &gt; 10 Explored by JWST Integral Field Spectroscopy: Hints of Rotating Disk Suggesting Weak Feedback. We investigate the dynamics of GN-z11, a luminous galaxy at z = 10.60, carefully analyzing the public deep integral field spectroscopy (IFS) data taken with the JWST NIRSpec integral field unit. While the observations of the IFS data originally targeted an He II clump near GN-z11, we find that the C III] λ λ1907, 1909 emission from ionized gas at GN-z11 is bright and spatially extended significantly beyond the point-spread function (PSF). The spatially extended C III] emission of GN-z11 shows a velocity gradient with red- and blueshifted components in the north and south directions, respectively, which cannot be explained by the variation of the [C III] λ1907/C III] λ1909 line ratios. Assuming the velocity gradient is produced by disk rotation, we perform forward modeling with GalPak3D, including the effects of PSF smearing and line blending, and obtain a rotation velocity of  vrot=257‑117+138  km s‑1, a velocity dispersion of  σv=91‑32+18  km s‑1, and a ratio of  vrot/σv=2.83‑1.41+1.82 . The v rot/σv value would suggest a rotation-dominated disk existing at z &gt; 10, albeit with large uncertainties. The rotation velocity agrees with those of numerical simulations predicting a rotating disk formed in the early Universe under the conditions of mass compaction and weak feedback. While the velocity gradient is consistent with the rotating-disk solution, we recognize that galactic outflows can also explain the velocity gradient, as well as the extended morphology and the high velocity dispersion found in the outskirts. Higher-signal-to-noise-ratio and higher-resolution data are necessary to conclude the physical origin of the velocity gradient in GN-z11.

Keywords: Early universe, Galaxy formation, Galaxy rotation, Galaxy disks, Galaxy kinematics, Galaxy evolution
New Measurements of the Lyα Forest Continuum and Effective Optical Depth with LyCAN and DESI Y1 Data. We present the Lyα Continuum Analysis Network (LyCAN), a convolutional neural network that predicts the unabsorbed quasar continuum within the rest-frame wavelength range of 1040–1600 Å based on the red side of the Lyα emission line (1216–1600 Å). We developed synthetic spectra based on a Gaussian mixture model representation of nonnegative matrix factorization (NMF) coefficients. These coefficients were derived from high-resolution, low-redshift (z &lt; 0.2) Hubble Space Telescope/Cosmic Origins Spectrograph (COS) quasar spectra. We supplemented this COS-based synthetic sample with an equal number of DESI Year 5 mock spectra. LyCAN performs extremely well on testing sets, achieving a median error in the forest region of 1.5% on the DESI mock sample, 2.0% on the COS-based synthetic sample, and 4.1% on the original COS spectra. LyCAN outperforms principal component analysis (PCA) and NMF-based prediction methods using the same training set by 40% or more. We predict the intrinsic continua of 83,635 DESI Year 1 spectra in the redshift range of 2.1 ≤ z ≤ 4.2 and perform an absolute measurement of the evolution of the effective optical depth. This is the largest sample employed to measure the optical depth evolution to date. We fit a power law of the form  τ(z)=τ0(1+z)γ  to our measurements and find τ 0 = (2.46 ± 0.14) × 10‑3 and γ = 3.62 ± 0.04. Our results show particular agreement with high-resolution, ground-based observations around z = 2, indicating that LyCAN is able to predict the quasar continuum in the forest region with only spectral information outside the forest.

Keywords: Cosmology, Large-scale structure of the universe, Lyman alpha forest, Convolutional neural networks, Intergalactic medium, Dark energy
Particles in Relativistic Magnetohydrodynamic Jets. II. Bridging Jet Dynamics with Multi–wave band Nonthermal Emission Signatures. Relativistic magnetized jets, originating near black holes, are observed to exhibit substructured flows. In this study, we present synthetic synchrotron-emission signatures for different lines of sight and frequencies, derived from three-dimensional relativistic magnetohydrodynamic simulations of pc-scale Active Galactic Nuclei jets. These simulations apply different injection nozzles, injecting steady, variable, and precessing jets. Extending our previous study, here, we have developed a bridge to connect jet dynamics and particle acceleration within relativistic shocks with nonthermal radiation dominant in jets. The emission is derived from Lagrangian particles—injected into the jet and following the fluid—accelerated through diffusive shock acceleration and subsequently cooled by emitting energy via synchrotron and inverse-Compton processes. Overall, the different shock structures lead to the formation of numerous localized emission patterns—interpreted as jet knots. These knot patterns can fade or flare, also as a consequence of merging or Doppler boosting, leading to jet variability. We find knots with high-enough pattern speed supposed to be visible as superluminal motion ≲5c. Synchrotron spectra of all jets reveal double-humped structures, reflecting multiple electron populations characterized by the nature of underlying shock and their age. The precessing jet is the most powerful emitter, featuring a spectrum flatter than the steady and the variable jet. The emission, although essentially governed by the acceleration through shocks, depends on the cooling history of the particle as well. Overall, the continuous reacceleration of electrons through shocks along the jet we found is an essential prerequisite for observing extended jet emission over large timescales and length scales.

Keywords: Magnetohydrodynamics, Radio jets, High energy astrophysics, Blazars, Relativistic jets, Active galactic nuclei, Shocks, Particle astrophysics
On the Properties of X-Ray Corona in Seyfert 1 Galaxies. We carried out a uniform and systematic analysis of a sample of 112 nearby bright Seyfert 1 type active galactic nuclei, the observations of which were carried out by the Nuclear Spectroscopic Telescope Array between 2013 August and 2022 May. The main goal of this analysis is to investigate the nature of the X-ray corona in Seyfert 1 galaxies. By fitting a physical model to the NuSTAR spectra, we could constrain the high-energy cutoff (E cut) for 73 sources in our sample. To estimate the temperature of the corona (kT  e ) in our sample of 112 sources, we used the Comptonization model to fit their spectra. We could constrain kT  e  in 42 sources. We found a strong positive correlation between E cut and kT  e , with most of the sources lying above the empirical approximation of E cut = 2‑3 kT  e . We investigated for possible correlations between various properties of the corona obtained from physical model fits to the observed spectra and between various coronal parameters and physical properties of the sources such as Eddington ratio and black hole mass. We found (a) a strong correlation between E cut and the photon index and (b) a significant negative correlation between kT  e  and the optical depth. From detailed statistical analysis of the correlation of coronal parameters with the Eddington ratio and black hole mass, we found no significant correlation. The correlations observed in this study indicate that an optically thin corona is needed to sustain a hotter corona with a steeper spectrum.

Keywords: Seyfert galaxies, Active galactic nuclei, X-ray active galactic nuclei
Evidence for Type Ib/c Origin of the Supernova Remnant G292.0+1.8. Circumstellar material (CSM) produced by mass loss from massive stars (≳10 M ⊙) through strong stellar winds or binary stripping provides rich information for understanding progenitors of core-collapse supernova remnants. In this paper we present a grating spectroscopy of a Galactic SNR G292.0+1.8, which is claimed to be a Type Ib/c remnant in a binary system according to recent studies. If G292.0+1.8 had experienced a strong mass-loss via binary interactions before its explosion, an oxygen-rich material produced in the He-burning layer is expected to be observed in the central belt-like structure formed by shock-heated CSM. Using the Reflection Grating Spectrometer onboard XMM-Newton, we detect N VII Lyα line (0.50 keV) for the first time in G292.0+1.8 and find that the abundance ratio of nitrogen to oxygen is significantly lower (N/O = 0.5 ± 0.1) than the solar value. This low N/O suggests that the progenitor of G292.0+1.8 experienced strong mass-loss and ended up as a Wolf─Rayet star exposing the He-burning layer at the presupernova. Comparing our result and the evolution models of single stars and binaries, we conclude that the progenitor of G292.0+1.8 experienced strong enough mass-loss to occur a Type Ib/c supernova. Our finding is another crucial piece of evidence for a stripped-envelope supernova such as Type Ib/c as the origin of G292.0+1.8.

Keywords: High energy astrophysics, Supernova remnants, Circumstellar matter, X-ray sources, Stellar evolution
Multidimensional Radiation Hydrodynamics Simulations of SN 1987A Shock Breakout. Shock breakout is the first electromagnetic signal from supernovae (SNe), which contains important information on the explosion energy and the size and chemical composition of the progenitor star. This paper presents the first two-dimensional (2D) multiwavelength radiation hydrodynamics simulations of SN 1987A shock breakout by using the CASTRO code with the OPAL opacity table considering eight photon groups from infrared to X-ray. To investigate the impact of the pre-SN environment of SN 1987A, we consider three possible circumstellar medium environments: a steady wind, an eruptive mass loss, and the existence of a companion star. In sum, the resulting breakout light curve has an hour-long duration and a peak luminosity of ∼4 × 1046 erg s‑1, with a decay rate of ∼3.5 mag hr‑1 in X-ray. The dominant band transits to UV around 3 hr after the initial breakout, and its luminosity has a decay rate of ∼1.5 mag hr‑1 that agrees well with the observed shock breakout tail. The detailed features of breakout emission are sensitive to the pre-explosion environment. Furthermore, our 2D simulations demonstrate the importance of multidimensional mixing and its impacts on shock dynamics and radiation emission. The mixing emerging from the shock breakout may lead to a global asymmetry of SN ejecta and affect its later SN remnant formation.

Keywords: Hydrodynamical simulations, Radiative transfer simulations, Ultraviolet astronomy, Shocks, Supernovae