Sazuna/UAT_keywords huggingface dataset:
The NuSTAR Local AGN N <SUB>H</SUB> Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe. Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of N H &gt; 1024 cm‑2. To tackle this issue, we present the NuSTAR Local AGN N H Distribution Survey (NuLANDS)—a legacy sample of 122 nearby (z &lt; 0.044) AGN primarily selected to have warm infrared colors from IRAS between 25 and 60 μm. We show that optically classified Type 1 and 2 AGN in NuLANDS are indistinguishable in terms of optical [O III] line flux and mid-to-far-infrared AGN continuum bolometric indicators, as expected from an isotropically selected AGN sample, while Type 2 AGN are deficient in terms of their observed hard X-ray flux. By testing many X-ray spectroscopic models, we show the measured line-of-sight column density varies on average by ∼1.4 orders of magnitude depending on the obscurer geometry. To circumvent such issues, we propagate the uncertainties per source into the parent column density distribution, finding a directly measured Compton-thick fraction of 35% ± 9%. By construction, our sample will miss sources affected by severe narrow-line reddening, and thus segregates sources dominated by small-scale nuclear obscuration from large-scale host-galaxy obscuration. This bias implies an even higher intrinsic obscured AGN fraction may be possible, although tests for additional biases arising from our infrared selection find no strong effects on the measured column density distribution. NuLANDS thus holds potential as an optimized sample for future follow-up with current and next-generation instruments aiming to study the local AGN population in an isotropic manner.

Keywords: Seyfert galaxies, Active galaxies, High energy astrophysics
B2 1308+326: A Changing-look Blazar or Not?. In our previous study, we identified a shift in the synchrotron peak frequency of the blazar B2 1308+326 from 1012.9 to 1014.8 Hz during a flare, suggesting it could be a changing-look blazar (CLB). In this work, we investigate the changing-look behaviour of B2 1308+326 by analysing a newly acquired optical spectrum and comparing it with an archival spectrum. We find that between the two epochs, the continuum flux increased by a factor of ~4.4, while the Mg II emission line flux decreased by a factor of 1.4 ± 0.2. Additionally, the equivalent width of the Mg II line reduced from ~20 to ~3 Å, indicating an apparent shift from a flat-spectrum radio quasar (FSRQ) class to a BL Lacertae (BL Lac) class. Despite this apparent change, the ratio of accretion disk luminosity to Eddington luminosity remains &gt;10‑2 during both epochs, indicating efficient accretion persists in B2 1308+326. The measured black hole mass remains consistent with an average  logMBH=8.44  M⊙. Our findings suggest that B2 1308+326 is not a genuine CLB but rather an intrinsic FSRQ that emerges as a BL Lac during high-flux states due to enhanced nonthermal emission.

Keywords: Blazars, Flat-spectrum radio quasars, Relativistic jets, Radio loud quasars, Active galactic nuclei
Detecting Solar Flare Precursors Using DEFT. The Detection and EUV Flare Tracking (DEFT) tool automatically identifies flare precursors in extreme ultraviolet (EUV) observations in a fast and consistent manner, with minimal computational overhead. DEFT currently uses GOES/SUVI 304 Å observations to detect, group, and flag sudden impulses that could be precursors to flares. In this study, we analyzed precursor signatures before 351 flares (150 C, 150 M, and 51 X class flares) that occurred from 2017 to date. Across these magnitudes, precursors were detected for 93% of the flares when using a 6 hr window before the flare start times. Using superposed epoch analysis, we found that elevated precursor activity tends to occur across all magnitude flares in the last 2 hr before the flares. The frequency of precursors gradually increases before M class flares but decreases for C class flares. We also found that in the last 20 minutes there is a significantly higher precursor frequency, pixel count, and power associated with M class flares than C class flares. We suggest that the observed EUV precursors are the observable signatures of small-scale magnetic reconnection events, and the consistently increasing frequency of precursor activity could indicate that the region is becoming increasingly unstable and reaching a critical stage that could result in flare initiation. Continuing research on EUV precursors is essential to better understand preflare processes that build and reduce magnetic instability prior to main-stage flares. The consistent and reliable detection and differentiation of EUV precursors could also complement and significantly improve current flare forecasting efforts.

Keywords: Astronomy image processing, Solar flares, Solar extreme ultraviolet emission
Morphology and Mach Number Distribution of Merger Shock Surfaces in Merging Galaxy Clusters. In a binary merger of two subclusters with comparable masses, a pair of merger shocks are typically generated, often manifesting as double radio relics. Using cosmological hydrodynamic simulations, we identify major merger events with mass ratio  1&lt;M1/M2≲4  and impact parameter b/rvir,1 ≲ 1, where rvir,1 is the virial radius of the heavier subcluster. We analyze merger shock surfaces approximately 1 Gyr after the pericenter passage, focusing on their morphology and the distribution of the Mach number, Ms, of their constituent shock zones. The shock surfaces exhibit an elongated shape with a minor-to-major axis ratio of ∼0.6–0.9 and cover the area of ∼5%‑20% of the enclosed sphere. The area ratio of the two shock surfaces roughly scales as  Ass,2/Ass,1∝M1/M2 , typically positioning the larger shock ahead of the lighter subcluster. The axis connecting the two subclusters generally does not pass through the centers of the shock surfaces, due to the nonzero impact parameter and ambient turbulent flows. The distribution of Ms of shock zones on each surface can be approximated by a log-normal function, peaking at Ms,peak ≈ 2‑4.5 and extending up to ∼10. The surface-area-weighted and X-ray- emissivity-weighted average Mach numbers are comparable, with  &lt;Ms&gt;area≈2.3–4.4  and  &lt;Ms&gt;X≈2–4 . In contrast, the cosmic-ray energy flux-weighted average Mach numbers are higher with  &lt;Ms&gt;CR≈3–5 . This discrepancy aligns with the differences between Mach numbers derived from X-ray and radio observations of radio relic shocks. On the other hand, we find that mostly  &lt;Ms&gt;X≳2  for simulated merger shocks, although shocks with MX-ray ≲ 2 are often reported in observations.

Keywords: Galaxy clusters, Shocks, Hydrodynamical simulations
CO Observations of the Type Ia Supernova Remnant 3C 397 by the Nobeyama 45 m Radio Telescope: Possible Evidence for the Single-degenerated Explosion. We present a new CO observation toward the Type Ia supernova remnant 3C 397 using the Nobeyama 45 m radio telescope at an unprecedented angular resolution of ∼18″. We newly found that the CO cloud at VLSR = 55.7–62.2 km s‑1 (60 km s‑1 cloud) shows a good spatial correspondence with the radio continuum shell. We also found an expanding gas motion of the 60 km s‑1 cloud with an expansion velocity of ∼3 km s‑1, which is thought to be formed by the pre- and/or postsupernova feedback. By considering the positions of Galactic spiral arms and the X-ray/H I absorption studies, we concluded that 3C 397 is physically associated with the 60 km s‑1 cloud rather than the previously known CO cloud at VLSR ∼ 30 km s‑1. Given that the previously measured preshock density is ∼2–5 cm‑3, the expanding motion of the 60 km s‑1 cloud was likely formed by the presupernova feedback known as optically thick wind. The scenario is consistent with the fact that 3C 397 exploded inside a wind-blown bubble as a single degenerate system.

Keywords: Supernova remnants, X-ray sources, Interstellar medium
Polarization of Gamma-Ray Burst Afterglows in the Context of Non-axisymmetric Structured Jets. As the most energetic explosion in the Universe, gamma-ray bursts (GRBs) are usually believed to be generated by relativistic jets. Some mechanisms (e.g., internal nonuniform magnetic dissipation processes or the precession of the central engine) may generate asymmetric jet structures, which are characterized by multiple fluctuations in the light curve of the afterglow. Since the jet's structure introduces asymmetry in radiation around the line of sight (LOS), it is naturally expected that polarization will be observable. In this work, we reveal the polarization characteristics of GRB afterglows with a non-axisymmetric structured jet. Our results show that the afterglow signal generally exhibits polarization, with the degree and evolution influenced by the specific jet structure, observing frequency, and the LOS. The polarization degree is notably higher when the LOS is outside the jet. This degree fluctuates over time as different regions of radiation alternate in their dominance, which is accompanied by the rotation of the polarization angle and further reflects the intricate nature of the jet. Regarding its evolution over frequency, the polarization degree displays significant fluctuations at spectral breaks, with the polarization angle possibly undergoing abrupt changes. These features may provide strong evidence for the future identification of potential GRBs with asymmetric jet structures.

Keywords: Gamma-ray bursts
Observational Evidence for a Correlation between the Magnetic Field of Jets and Star Formation Rate in Host Galaxies. Accretion supermassive black holes in the center of active galaxies usually produce "jet"-collimated bipolar outflows of relativistic particles. Magnetic fields near the black hole event horizon may play a crucial role in the formation of jets/outflows. Both theory and observation indicate that jets/outflows driven by centrally active supermassive black holes have a feedback effect on the overall properties of the host galaxies. Therefore, the magnetic field is a key ingredient for the formation and evolution of galaxies. Here, we report a clear correlation between the magnetic field of jets and star formation rate for a large sample of 96 galaxies hosting supermassive black holes, which suggests that the star formation of active galactic nuclei host galaxies may be powered by the jets.

Keywords: Star formation, Supermassive black holes, Active galactic nuclei, AGN host galaxies
Mass Transfer in Eccentric Black Hole–Neutron Star Mergers. Black hole–neutron star binaries are of interest in many ways: they are intrinsically transient, radiate gravitational waves detectable by LIGO, and may produce γ-ray bursts. Although it has long been assumed that their late-stage orbital evolution is driven entirely by gravitational wave emission, we show here that in certain circumstances, mass transfer from the neutron star onto the black hole can both alter the binary's orbital evolution and significantly reduce the neutron star's mass: when the fraction of its mass transferred per orbit is ≳10‑2, the neutron star's mass diminishes by order unity, leading to mergers in which the neutron star mass is exceptionally small. The mass transfer creates a gas disk around the black hole before merger that can be comparable in mass to the debris remaining after merger, i.e., ~0.1 M⊙. These processes are most important when the initial neutron star–black hole mass ratio q is in the range ≈0.2–0.8, the orbital semimajor axis is 40 ≲ a0/rg ≲ 300 (rg ≡ GMBH/c2), and the eccentricity is large at e0 ≳ 0.8. Systems of this sort may be generated through the dynamical evolution of a triple system, as well as by other means.

Keywords: Neutron stars, Roche lobe overflow, General relativity, Astrophysical black holes
Understanding the Radio Emission from the β Cep Star V2187 Cyg. We analyze the radio emission from the β Cep star V2187 Cyg using archive data from the Jansky Very Large Array. The observations were made in ten epochs at 1.39 and 4.96 GHz in the highest angular resolution A configuration. We determine a spectral index of of α = 0.6 ± 0.2 (Sν ∝ να), consistent with an ionized wind or a partially optically thick synchrotron or gyrosynchrotron source. The emission is spatially unresolved at both frequencies. The 4.96 GHz data show a radio pulse with a duration of about one month that can be modeled in terms of an internal shock in the stellar wind produced by a sudden increase in the mass-loss rate and the terminal velocity. The quiescent radio emission of V2187 Cyg at 4.96 GHz (with a flux density of ≃150 μJy) cannot be explained in terms of an internally (by V2187 Cyg) or externally (by a nearby O star) photoionized wind. We conclude that, despite the spectral index suggestive of free–free emission from an ionized wind, the radio emission of V2187 Cyg most likely has a magnetic origin, a possibility that can be tested with a sensitive search for circular polarization in the radio, as expected from gyrosynchrotron radiation and also by trying to measure the stellar magnetic field, which is expected to be in the range of several kilogauss.

Keywords: Beta Cephei variable stars, Magnetic stars
Identifying the Coronal Holes in Open Magnetic Field Regions Using Deep Learning. Open magnetic field (OMF) regions are the foot points of the field lines extending to infinity. While they are often considered to coincide with coronal holes (CHs), many studies have reported non-negligible inconsistency between the two. The objective of this study is to develop a deep learning model to predict the OMF regions that coincide with CHs, and to examine the importance of different physical quantities on the prediction. The CHs and OMF regions are both identified from the coronal data computed by a magnetohydrodynamic model developed by Predictive Science. Eight physical quantities, colatitude, magnetic flux expansion factor, magnetic field strength, thermal pressure, electron temperature, electron number density, mass density, and local coronal heating rate, at the OMF footpoints are used as the input to the deep learning model. The results of the test set indicate that the model improves the consistency between CHs and OMF regions from 0.33 to 0.81, and that all eight quantities are similarly important when they are all included in the model although the prediction accuracy would be most affected by excluding the colatitude and/or magnetic field strength. Comparison between the histograms of CH and non-CH open field regions indicates that each quantity alone can be used to distinguish the two within the ranges of values where one histogram is much higher than the other.

Keywords: Magnetohydrodynamics, Solar extreme ultraviolet emission, Neural networks, Classification, Solar corona, Solar magnetic fields, Solar coronal holes
EDGE-INFERNO: Simulating Every Observable Star in Faint Dwarf Galaxies and Their Consequences for Resolved-star Photometric Surveys. Interpretation of data from faint dwarf galaxies is made challenging by observations limited to only the brightest stars. We present a major improvement to tackle this challenge by undertaking zoomed cosmological simulations that resolve the evolution of all individual stars more massive than 0.5 M⊙, thereby explicitly tracking all observable stars for the Hubble time. For the first time, we predict observable color–magnitude diagrams and the spatial distribution of ≈100,000 stars within four faint (M⋆ ≈ 105 M⊙) dwarf galaxies directly from their cosmological initial conditions. In all cases, simulations predict complex light profiles with multiple components, implying that typical observational measures of structural parameters can make the total V-band magnitudes appear up to 0.5 mag dimmer compared to estimates from simulations. Furthermore, when only small (⪅100) numbers of stars are observable, shot noise from realizations of the color–magnitude diagram introduces uncertainties comparable to the population scatter in, e.g., the total magnitude, half-light radius, and mean iron abundance measurements. Estimating these uncertainties with fully self-consistent mass growth, star formation, and chemical enrichment histories paves the way for more robust interpretation of dwarf galaxy data.

Keywords: Galaxy formation, Dwarf galaxies, Galaxy properties
Analysis of Polarized Dust Emission Using Data from the First Flight of SPIDER. Using data from the first flight of SPIDER and from the Planck High Frequency Instrument, we probe the properties of polarized emission from interstellar dust in the SPIDER observing region. Component-separation algorithms operating in both the spatial and harmonic domains are applied to probe their consistency and to quantify modeling errors associated with their assumptions. Analyses of diffuse Galactic dust emission spanning the full SPIDER region demonstrate (i) a spectral energy distribution that is broadly consistent with a modified-blackbody (MBB) model with a spectral index of β d = 1.45 ± 0.05 (1.47 ± 0.06) for E (B)-mode polarization, slightly lower than that reported by Planck for the full sky; (ii) an angular power spectrum broadly consistent with a power law; and (iii) no significant detection of line-of-sight polarization decorrelation. Tests of several modeling uncertainties find only a modest impact (∼10% in σ  r ) on SPIDER's sensitivity to the cosmological tensor-to-scalar ratio. The size of the SPIDER region further allows for a statistically meaningful analysis of the variation in foreground properties within it. Assuming a fixed dust temperature T d = 19.6 K, an analysis of two independent subregions of that field results in inferred values of β d = 1.52 ± 0.06 and β d = 1.09 ± 0.09, which are inconsistent at the 3.9σ level. Furthermore, a joint analysis of SPIDER and Planck 217 and 353 GHz data within one subregion is inconsistent with a simple MBB at more than 3σ, assuming a common morphology of polarized dust emission over the full range of frequencies. This evidence of variation may inform the component-separation approaches of future cosmic microwave background polarization experiments.

Keywords: Observational cosmology, Interstellar emissions, Cosmic microwave background radiation
Ejective Feedback as a Quenching Mechanism in the First 1.5 Billion Years of the Universe: Detection of Neutral Gas Outflow in a z = 4 Recently Quenched Galaxy. The confirmation of massive quiescent galaxies emerging within the first billion years of the Universe poses intriguing questions about the mechanisms of galaxy formation. There must be highly efficient processes at work to shut down star formation in galaxies at cosmic dawn. I present the detection of neutral outflowing gas in a massive recently quenched galaxy at z = 4, showing ejective back as a quenching mechanism. Based on James Webb Space Telescope spectrum, the star formation rate (SFR) of this has been declining with a rapid e-folding timescale of ∼50 Myr. The current specific SFR is 5 × 10‑11 yr‑1, roughly 40 times lower than that of the star-forming main sequence at comparable redshifts. Emission-line ratios of [Ne III]/[O II] and [O III]/Hβ are similar to active galactic nuclei (AGNs) at comparable redshifts. A series of Fe II and Mg II absorption lines appear blueshifted by ∼250 km s‑1 relative to the stellar continuum, suggesting an outflow of neutral gas. The estimated mass outflow rate is approximately 7 times greater than the SFR derived from the stellar continuum, implying that the suppression of star formation is likely due to gas being depleted by the outflow. If the emission lines are AGN-driven, the AGN can also provide sufficient energy to launch the outflow observed. This galaxy represents the most distant example of its kind known to date. This study offers a compelling explanation for the existence of massive quiescent galaxies in the first billion years of the Universe.

Keywords: AGN host galaxies, Galaxies, Quenched galaxies, Galaxy winds, Galaxy evolution, Interstellar medium, Galaxy quenching, Galaxy spectroscopy, High-redshift galaxies, Post-starburst galaxies
In Search of Extraterrestrial Artificial Intelligence Through Dyson Sphere–like Structures around Primordial Black Holes. Are we alone? It is a compelling question that human beings have confronted for centuries. The search for extraterrestrial life is a broad range of quests for finding simple forms of life up to intelligent beings in the Universe. The plausible assumption is that there is a chance that intelligent life will be followed by advanced civilization equipped or even dominated by artificial intelligence (AI). In this work, we categorize advanced civilizations (on an equal footing, an AI-dominated civilization) on the Kardashev scale. We propose a new scale known as the space exploration distance to measure civilization advancement. We propose a relation between this length and the Kardashev scale. Then, we suggest the idea that advanced civilizations will use primordial black holes (PBHs) as sources of harvesting energy. We calculate the energy harvested by calculating the space exploration distance. Finally, we propose an observational method to detect the possibility of extraterrestrial AI using Dyson sphere–like structures around PBHs in the Milky Way and other galaxies.

Keywords: Search for extraterrestrial intelligence, Astrobiology, Primordial black holes
Shock Breakouts from Compact Circumstellar Medium Surrounding Core-collapse Supernova Progenitors May Contribute Significantly to the Observed ≳10 TeV Neutrino Background. Growing observational evidence suggests that enhanced mass loss from the progenitors of core-collapse supernovae (SNe) is common during ~1 yr preceding the explosion, creating an optically thick circumstellar medium (CSM) shell at ~1014.5 cm radii. We show that if such mass loss is indeed common, then the breakout of the SN shock through the dense CSM shell produces a neutrino flux that may account for a significant fraction of the observed ≳10 TeV neutrino background. The neutrinos are created within a few days from the explosion, during and shortly after the shock breakout, which produces also large UV (and later X-ray) luminosity. The compact size and large UV luminosity imply a pair production optical depth of ~104 for &gt; 100 GeV photons, naturally accounting for the lack of a high-energy gamma-ray background accompanying the neutrino background. SNe producing &gt;1 neutrino event in a 1 km2 detector are expected at a rate of ≲0.1 yr‑1. A quantitative theory describing the evolution of the electromagnetic spectrum during a breakout, as the radiation-mediated shock is transformed into a collisionless one, is required to enable (i) using data from upcoming surveys that will systematically detect large numbers of young, &lt;1 day old SNe to determine the preexplosion mass-loss history of the SN progenitor population, and (ii) a quantitative determination of the neutrino luminosity and spectrum.

Keywords: Neutrino astronomy, Supernovae, High energy astrophysics