Sazuna/UAT_keywords huggingface dataset:
Low-angular-momentum Black Hole Accretion: First General Relativistic Magnetohydrodynamic Evidence of Standing Shocks. Understanding the dynamics of low-angular-momentum accretion flow around black holes (BHs) is essential for probing extreme plasma behavior in strong gravity, where shock formation can naturally produce variability signatures. In this paper, we perform general relativistic magnetohydrodynamic (GRMHD) simulations of low angular momentum accretion flows onto a BH with different BH spins to investigate the accretion dynamics near the central BH region. The simulation results show the standard and normal evolution regime in all cases. In particular, we report the formation and persistence of standing shocks in low-angular-momentum accretion flows using multidimensional (2D and 3D) GRMHD simulations for the first time. Previous studies did not detect such stable standing shock structures, making our findings a significant advancement in this field. The finding of shock dynamics can be further associated with some radiation features, such as flares observed in Sgr A* and quasiperiodic oscillation signals detected in some X-ray binaries and active galactic nuclei.

Keywords: Accretion
<SUP>63</SUP>Fe–<SUP>63</SUP>Mn: A Possible Strong Urca Pair and Its Potential Astrophysical Impact. The cooling strength of the Urca pair, 63Fe–63Mn, exhibits an extensive range of variation due to the uncertainty in the spin parity of the ground state of 63Fe. To investigate the cooling effect of this Urca pair on the thermal evolution of neutron star crusts, we performed simulations on neutron star structure and evolution under various spin-parity assignment scenarios. When adopting recently evaluated nuclear data, 63Fe–63Mn emerges as one of the strongest Urca pairs. In the case of MAXI J0556-332, 63Fe–63Mn is the only pair above the shallow heating layer, significantly impacting the cooling curve and the superburst ignition. Moreover, the constraint on the past nucleosynthesis reduced to one-quarter of its original value, falling within three decades, which enables the validation of nuclear reaction theories in the outer layers of neutron stars. Our results highlight the need for more precise measurements of the β‑ decay of 63Mn to better determine the Urca cooling effect of the 63Fe–63Mn pair in accreted neutron star crusts.

Keywords: Neutron stars, Urca process, X-ray binary stars
On the Correlation between Alfvén Waves and Auroral Radio Emissions in the Jovian System. Jupiter's powerful aurorae reflect intense energy dissipation in the magnetosphere–ionosphere system. Recent studies reveal that solar wind compression systematically enhances auroral emission, while the mechanism is not yet fully understood. Alfvén waves were proposed to be responsible for the auroral enhancement, based on the correlation between Alfvénic wave power and ultraviolet auroral intensity revealed by the unprecedented, though limited, observations of Juno and the Hubble Space Telescope. Since auroral energy dissipation produces emissions across multiple frequency bands, we leverage a comprehensive data set of radio emissions from Juno to investigate the relation between Alfvén waves and auroral radiation power. A clear correlation between Alfvén waves and radio emissions was revealed, providing additional supporting evidence for the hypothesis that Alfvén waves contribute to auroral energy dissipation, and the correlation peaked in the region between 40 and 60 RJ, providing key insights to the Alfvénic energy source region in the magnetosphere.

Keywords: Planetary magnetospheres, Alfven waves, Magnetospheric radio emissions, Jupiter
Timing and Spectral Studies of SRGA J144459.2−604207 with NICER, Einstein Probe, IXPE, NuSTAR, Insight-HXMT, and INTEGRAL During its 2024 Outburst. SRGA J144459.2−604207 is a newly confirmed accreting millisecond X-ray pulsar and type I X-ray burster. We present the broadband X-ray timing and spectral behaviors of SRGA J144459.2−604207 during its 2024 outburst. The data were collected from NICER, Einstein Probe, Imaging X-ray Polarimetry Explorer (IXPE), Insight Hard X-ray Modulation Telescope (Insight-HXMT), NuSTAR, and INTEGRAL observations. X-ray pulsations have been detected for the 1.5─90 keV energy range throughout the "ON" phase of the outburst from MJD ∼ 60355─60385. We refined the orbital and spin ephemerides assuming a circular orbit, and found that the pulsar was in a spin-up state during MJD ∼ 60361─60377 showing a significant spin-up rate  ν̇  of (3.15 ± 0.36) × 10−13 Hz s−1. Around MJD ∼ 60377 a swing was detected in the spin evolution accompanied by significantly enhanced pulsed emission. We studied the pulse-profile morphology during the X-ray bursts as observed by Insight-HXMT, IXPE, and NuSTAR. During the bursts, pulsations were detected across the 2─60 keV with shapes broadly consistent with those observed for the persistent emission. We found, however, that the "burst" pulse profiles exhibit significant phase offsets relative to the pre- and postburst profiles. These offsets systematically decrease with increasing energy, ∆ϕ ≍ 0.15, 0.11, and 0.02 for IXPE, Insight-HXMT ME, and HE in 2─8, 5─30, and 20─60 keV, respectively, and ∆ϕ ≍ 0.21, 0.10, and 0.07 for NuSTAR in 3─10, 20─35, and 35─60 keV, respectively, compared to the pre- and postburst profiles. We performed a joint spectral analysis of quasi-simultaneous NICER, NuSTAR, and Insight-HXMT data for two epochs. The resulting spectra from both observations were consistent and well described by an absorbed thermal Comptonization model, nthcomp, plus relativistic reflection, relxillCp.

Keywords: Neutron stars, Millisecond pulsars, Low-mass x-ray binary stars, Pulsars
The Complex Multiwavelength Morphology of the Peculiar Compact Galaxy Group IC 2431. We present new Chandra X-ray imaging spectroscopy of the compact galaxy group IC 2431, and compare with archival ultraviolet, optical, infrared, and radio images. IC 2431 is a starburst system containing three tidally distorted disk galaxies. All three galaxies may have active nuclei. One galaxy is classified as an active galactic nucleus (AGN) based on its optical spectrum, a second is identified as a possible X-ray AGN based on the Chandra data, and the third galaxy may host a radio AGN. In optical images, a prominent dust lane crosses the southern galaxy, while Spitzer infrared images show a dusty bridge connecting the two brightest galaxies. Chandra maps reveal a massive (2 × 107 M⊙) concentration of hot gas between these two galaxies, as well as several other knots of hot gas and nonthermal emission. The unabsorbed X-ray luminosity of the hot gas in IC 2431 is ∼1 × 1042 erg s−1, which is enhanced by about a factor of 4 relative to the star formation rate, compared to other star-forming galaxies. In radio maps, a bright jet/ridge of radio continuum emission extends 4 kpc from one nucleus. We compare the properties of IC 2431 with those of other interacting galaxy systems, and discuss two different scenarios that may account for the peculiarities of IC 2431: ram pressure stripping of the interstellar medium during a head-on collision between two galaxies, or an AGN-powered radio jet that has been distorted by an interaction with interstellar gas during a tidal encounter between galaxies.

Keywords: AGN host galaxies, Starburst galaxies, Active galactic nuclei, Galaxy groups
Anisotropy of Core-collapse Supernovae Effected by the Disks of Active Galactic Nuclei. Active galactic nuclei (AGN) disks provide dense environments that influence star formation, evolution, and migration. In AGN disks, pressure gradients and migration accelerations could create the anisotropy of the core-collapse supernovae that occurs when massive stars explode at the end of their lives. In this study, we construct equilibrium equations by considering these two factors and then compute the light curves for three types of progenitor stars at different locations of AGN disks for different supermassive black hole (SMBH) masses, accretion efficiencies, explosion energies, and masses of ejecta. The results show that the migration acceleration has more significant effects on the anisotropic explosions than the pressure gradients of the AGN disks. The anisotropic luminosities are pronounced at large radii, and massive SMBHs would suppress the anisotropy and reduce the total luminosity.

Keywords: Stellar winds, Galaxy accretion disks, Core-collapse supernovae
Investigating the Correlation between ZTF Tidal Disruption Events and IceCube High-energy Neutrinos. Investigating the correlation between the tidal disruption event (TDE) population and IceCube neutrinos could help us better understand whether TDEs could be potential high-energy neutrino emitters. In this paper, we perform a systematic search for TDEs that are associated with neutrinos in a sample including 143 IceCube neutrino alert events and 52 TDEs classified by the Zwicky Transient Facility Bright Transient Survey. Furthermore, considering that the TDEs/TDE candidates reported as potential IceCube neutrino emitters are all accompanied by infrared (IR) echo emission, we further select TDEs with IR echoes from these 52 TDEs as a subsample to examine their correlation with neutrinos. Based on the Wide-field Infrared Survey Explorer mission database, seven TDEs are identified as having IR echoes. Then we employ Monte Carlo simulations to quantify the correlation between the TDE sample/subsample and IceCube neutrinos. Finally, after considering spatial and temporal criteria, the seven TDEs with IR echoes show the most significant correlation at the 2.46σ confidence level. If we tentatively further take the time delay factor into account, the correlation enhances to the 2.66σ confidence level. The correlation is primarily contributed by two TDEs: AT2019dsg and AT2019azh. The latter's association with a neutrino alert, IC230217A, is newly reported in this work. We discuss the possible physical connection between AT2019azh and the neutrino event IC230217A.

Keywords: High energy astrophysics, Neutrino astronomy, Tidal disruption
Production of Radioactive <SUP>22</SUP>Na in Core-collapse Supernovae: The Ne-E(L) Component in Presolar Grains and Its Possible Consequences on Supernova Observations. Presolar graphite grains carry the isotopic signatures of their parent stars. A significant fraction of presolar graphites show isotopic abundance anomalies relative to solar for elements such as O, Si, Mg, and Ca, which are compatible with nucleosynthesis in core-collapse supernovae (CCSNe). Therefore, they must have condensed from CCSN ejecta before the formation of the Sun. Their most puzzling abundance signature is the 22Ne-enriched component Ne-E(L), interpreted as the effect of the radioactive decay of 22Na (T1/2 = 2.6 yr). Previous works have shown that if H is ingested into the He shell and not fully destroyed before the explosion, the CCSN shock in the He-shell material produces large amounts of 22Na. Here we focus on such CCSN models, showing a radioactive 26Al production compatible with grain measurements, and analyze the conditions of 22Na nucleosynthesis. In these models, 22Na is mostly made in the He shell, with a total ejected mass varying between 2.6 × 10−3 M⊙ and 1.9 × 10−6 M⊙. We show that such 22Na may already impact the CCSN light curve 500 days after the explosion, and at later stages it can be the main source powering the CCSN light curve for up to a few years before 44Ti decay becomes dominant. Based on the CCSN yields above, the 1274.53 keV γ-ray flux due to 22Na decay could be observable for years after the first CCSN light is detected, depending on the distance. This makes CCSNe possible sites to detect a 22Na γ-ray signature consistently with the Ne-E(L) component found in presolar graphites. Finally, we discuss the potential contribution from 22Na decay to the Galactic positron annihilation rate.

Keywords: Supernovae, Core-collapse supernovae
Ab Initio Entropy Calculations of Water Predict the Interiors of Uranus and Neptune to Be 15%–30% Colder than Previous Models. Ab initio free energy calculations are employed to derive the entropy of liquid and superionic water over a wide range of conditions in the interiors of Uranus and Neptune. The resulting adiabats are much shallower in pressure–temperature space than those adopted for earlier models of Uranus and Neptune. Our models for their interiors are thus much colder, increasing the likelihood that diamond rain or the recently predicted phase separation of planetary ices has occurred in the mantles of ice giant planets. Based on our ab initio data, we construct interior models for Uranus and Neptune with the concentric MacLaurin spheroid method that match the existing gravity measurements. We compare fully convective models with models that include a convective boundary between liquid and superionic water. We also share a code to characterize giant planet atmospheres where para- and ortho-hydrogen as well as helium are present.

Keywords: Neptune, Solar system planets, Planetary interior, Extrasolar ice giants, Uranus
A Prediction of Solar Cycle Maxima Using Visibility Graphs. We apply a complex network approach to analyze the time series of five solar parameters, and propose a strategy to predict the number of sunspots for the next solar maximum, and when this maximum will occur. The approach is based on the visibility graph (VG) algorithm, and a slightly modified version of it, the horizontal VG, which maps a time series into a complex network. Various network metrics exhibit either an exponential or a scale-free behavior, and we find that the evolution of the characteristic decay exponents is consistent with variations of the sunspot number along solar cycles. During solar minimum, the sunspot number and the F10.7 cm radio flux time series have characteristic decay exponents that correlate well with the next maximum sunspot number, suggesting that they may be good precursors of the intensity of the next solar maximum.

Keywords: Solar activity, Solar physics, Solar cycle
Insights from the "Red Devil" AT 2022fpx: A Dust-reddened Family of Tidal Disruption Events Excluded by Their Apparent Red Color?. We report unnoticed but intriguing features in the peculiar nuclear transient AT 2022fpx, and investigate its type. These features include the constantly red optical color of g ‑ r &gt; 0, a stable soft X-ray flare (kT ∼ 100 eV) in the past ∼550 days, a prominent mid-infrared echo peaked at ∼1043.3 erg s‑1, and the confirmation of a weak active galactic nucleus by weak flares in pre-event Wide-field Infrared Survey Explorer mid-infrared light curves with no contemporary optical, radio or X-ray counterparts. The combination of the optical red color and possible origin of a tidal disruption event (TDE) in AT 2022fpx is particularly attractive, as it challenges the most widely accepted and adopted "blue color" criterion for optical TDE selection. Although we still cannot confirm whether the red color is intrinsic, we do find that the "blue color" criterion can filter out normal TDEs whose optical–UV spectral energy distributions (SEDs) are either severely contaminated by prominent emission lines (especially Hα) or heavily dust-reddened. Hence, its potential selection effect may have been imprinted on the whole optical TDE family. Blackbody fitting on the optical (rest-frame ∼4000–7000 Å) and optical–UV (∼2000–7000 Å) SEDs of four TDEs with high-cadence UV observations shows that Tbb rises by ∼40%‑110% when the UV bands are included. The power-law models (fλ ∝ λ‑α with α = 2–3) can fit the rest-frame ∼2000–7000 Å SEDs more consistently, indicating that SEDs should peak at shorter wavelengths, than simple blackbodies. Hence, the estimated released energy for the optical–UV-bright but X-ray-faint TDEs based on blackbody SED fitting should be significantly lower than the intrinsic energy.

Keywords: Supermassive black holes, Black holes, Tidal disruption, Transient sources, Time domain astronomy
Cross Calibration of Galaxy Cluster Temperatures Measured with NuSTAR, XMM-Newton, and Chandra. The use of galaxy clusters to constrain cosmology is limited in part due to uncertainties in derived cluster masses, which often depend on the gas temperature. Unfortunately, there exists a longstanding discrepancy in temperature measurements of the same galaxy clusters made by the two most sensitive X-ray observatories, Chandra and XMM-Newton. The NuSTAR X-ray Observatory's greater sensitivity to the exponential turnover in the bremsstrahlung continuum allows for more precise and potentially more accurate galaxy cluster temperature estimates, especially given its unique ability to independently calibrate its optics in orbit. We present new NuSTAR spectra of 10 relaxed (5 keV &lt; kT &lt; 10 keV) clusters, extracted from identical regions as previous spectra from Chandra and XMM-Newton. The 3─20 keV spectra are well fit by single temperature models, and fits done in narrower bandpasses provide no clear evidence in support of the existence of multi-temperature gas. We find NuSTAR temperatures are typically ∼15% higher than XMM-Newton temperatures. In contrast, good agreement is found between NuSTAR and Chandra temperatures for clusters with kT ≲ 7 keV, with Chandra measurements exceeding NuSTAR's in hotter systems. When more clusters are included, the trend is reinforced and can be extended to higher temperatures. A generic increase to Chandra's E &gt; 2 keV effective area (∼5% at 5 keV) is found to explain the trend reasonably well. These results demonstrate the potential for NuSTAR data to address the two-decade-old temperature discrepancy between Chandra and XMM-Newton.

Keywords: Galaxy clusters, Cosmology, X-ray astronomy, Galactic and extragalactic astronomy, Calibration, Telescopes
Analysis of WISPR Images of the Near-Sun Heliospheric Current Sheet Region from Parker Solar Probe Encounters 4 and 5 and Comparison with the in Situ Observations. We present an analysis of Wide-field Imager for Solar PRobe (WISPR) images of the near-Sun heliospheric current sheet (HCS) region from the Parker Solar Probe (PSP) in 2020 January and June. Previous analysis of the solar wind data from PSP's in situ instruments for these periods has shown multiple signatures of magnetic reconnection during HCS encounters. The signatures, including field line disconnections, density enhancements, and reconnection flows, indicated that reconnection was nearly always active in the HCS near the Sun. Here, we present an analysis of WISPR white-light observations of the HCS region during the same time periods, using an image-processing technique that enhances changes in the images from frame to frame. This processing reveals the presence of a nearly continual stream of transient density enhancements ("blobs") within the helmet streamer flow not evident in the standard calibrated-brightness images. The blobs, observed frequently in the helmet streamer flows by white-light imagers, are broadly interpreted as resulting from reconnection in the vicinity of the HCS. Thus, the WISPR observations are consistent with the in situ data finding that reconnection is almost always active in the HCS near the Sun. We use the Tracking and Fitting technique to determine the trajectory and size of a few of the more distinct blobs. We confirm that the blobs lie near the HCS and find that the sizes of the imaged blobs are similar to the size estimates for possible blobs seen in situ in the HCS at similar distances from the Sun.

Keywords: Slow solar wind, Active solar corona, Solar coronal streamers
Magnetic White Dwarfs in the SDSS 100 pc Sample: Further Evidence of Two Formation Channels. We conduct a model atmosphere analysis on all magnetic white dwarfs (MWDs) in the Sloan Digital Sky Survey (SDSS) 100 pc sample. We have 163 magnetic targets in this sample, 87 of which are new discoveries, making this the largest volume-limited survey of MWDs to date. We discuss the distribution of multiple parameters, including mass, cooling age, and field strength. We find strong evidence of two populations of MWDs that form through separate mechanisms based on a cluster analysis of these parameters. The young, high-mass objects typically have high field strengths which indicate a merger origin, while old, average-mass objects have weaker fields that likely originated through a crystallization-induced dynamo or previous evolution stages. When comparing young and old objects, two-sample Kolmogorov─Smirnov tests yield statistically significant differences between the field strengths and masses of the magnetic targets. We use a Gaussian mixture model to identify where these populations lie in parameter space, and we find two groups centered at distinct cooling ages, masses, and field strengths of 2.9 Gyr, 0.71 M⊙, 3.7 MG and 1.8 Gyr, 0.96 M⊙, 84 MG, respectively. Our results further support the dual formation channel previously reported in the literature. The occurrence of magnetism strongly correlates with the onset of crystallization. However, given the breakout times required for a crystallization dynamo, we find that many of our older, average-mass objects can be better explained with a core-convective dynamo that forms on the main sequence.

Keywords: White dwarf stars, Stellar magnetic fields, Compact objects, Stellar masses, Stellar evolution
The Influence of Interplanetary Magnetic Field Orientations on the Martian Bow Shock and Magnetosheath Magnetic Field. Unlike Earth, Mars lacks a global intrinsic magnetic field but has regional crustal magnetic fields concentrated in its southern hemisphere. This unique configuration leads to distinctive interactions with the solar wind. In this study, we have investigated the influence of the interplanetary magnetic field (IMF) orientation on the Martian bow shock (BS) and the magnetosheath magnetic field, using data from the Mars Atmosphere and Volatile Evolution mission from the years 2014 to 2020. Our results have demonstrated that the IMF orientation can significantly affect the location of the Martian BS and the magnitude of the magnetosheath magnetic field. Compared to nonradial IMF conditions, radial IMF conditions bring the Martian BS closer to the planetary surface. Additionally, under radial IMF conditions, the proportional increase in the magnetic field magnitude from the solar wind to the dayside magnetosheath is smaller, due to the absence of magnetic pileup processes. However, under both nonradial and radial IMF conditions, the proportional increases in the magnetic field magnitude from the solar wind to the terminator and nightside magnetosheath are similar. Moreover, both the Martian BS and the magnetosheath magnetic field magnitude exhibit dawn–dusk and north–south asymmetries. These asymmetries are determined by both the orientation of the IMF and the presence of regional crustal magnetic fields. Our results suggest that the IMF orientation plays a crucial role in the interaction between the solar wind and Mars.

Keywords: Solar-planetary interactions, Mars, Planetary bow shocks, Interplanetary magnetic fields