Sazuna/UAT_keywords huggingface dataset:
Prediscovery Activity of New Interstellar Object 3I/ATLAS: Rapid Brightening from 6 to 4 au. We report on the prediscovery observations and constraints of the new interstellar comet 3I/2025 N1 (ATLAS), made by the Zwicky Transient Facility, for the inbound leg of the comet out to a heliocentric distance of rh = 17 au, or approximately a year before its discovery. We find that 3I/ATLAS has been active inward of a heliocentric distance of at least rh = 6.5 au. The comet followed a brightening rate of  ∝rh−3.8 , which is significantly steeper than that of the only other known interstellar comet, 2I/Borisov, and is more consistent with dynamically old long-period comets and short-period comets in the solar system. By measuring the brightening of the dust coma, we estimate that 3I had a dust production rate of  Mḋ∼5kgs−1  in 2025 early May (rh ∼ 6 au), increasing to  Mḋ∼30kgs−1  toward 2025 mid-July (rh ∼ 4 au) assuming 100 μm dust grains, in line with the more recent Hubble Space Telescope measurement made at rh = 3.8 au. Comparison with the prediscovery photometry by the Transiting Exoplanet Survey Satellite suggested that 3I started producing constant dust outflow probably around rh ∼ 9 au, coinciding with the turn-on distance of CO2 ice. We also conduct a deep search of 3I/ATLAS with multiple nights of data taken in 2024, when the comet was at rh = 13─17 au, and conclude that the comet was no brighter than 2─5 mag above the coma or bare-nucleus lightcurves. This suggests that the comet did not exhibit strong outbursts during these periods, consistent with 2I/Borisov as well as most long-period solar system comets.

Keywords: Comets, Interstellar objects
Direct Observation of the X-Ray Counterpart of the Hα Filaments and of the Sloshing Spiral in the Perseus Galaxy Cluster. Deep Chandra observations of the Perseus galaxy cluster have allowed for the discovery of X-ray counterparts to the Hα filamentary structures and of a sloshing spiral. However, both components are extremely faint, and their study is largely hindered by the volume-filling hot intracluster medium. Using the Poisson general morphological component analysis algorithm, a blind source separation method adapted for Poissonian statistics, we were able to extract detailed, clean morphological maps of these components. We then introduced a template fitting method to investigate their spectral characteristics. We report the first direct observation of ∼1.35 keV low-energy emission from the sloshing spiral, and produce the most detailed and unpolluted map of the X-ray filaments thus far obtained.

Keywords: Galaxy clusters, X-ray astronomy, Perseus Cluster
Electromagnetic Observables of Weakly Collisional Black Hole Accretion. The black holes in the Event Horizon Telescope sources Messier 87* and Sagittarius A* (Sgr A*) are embedded in a hot, collisionless plasma that is fully described in kinetic theory yet is usually modeled as an ideal, magnetized fluid. In this Letter, we present results from a new set of weakly collisional fluid simulations in which leading-order kinetic effects are modeled as viscosity and heat conduction. Consistent with earlier, lower-resolution studies, we find that overall flow dynamics remain very similar between ideal and nonideal models. For the first time, we synthesize images and spectra of Sgr A* from weakly collisional models—assuming an isotropic, thermal population of electrons—and find that these remain largely indistinguishable from ideal fluid predictions. However, most weakly collisional models exhibit lower light-curve variability, with all magnetically dominated models showing a small but systematic decrease in variability.

Keywords: Accretion, Black hole physics, Plasma astrophysics, Low-luminosity active galactic nuclei, Relativistic fluid dynamics, Magnetohydrodynamical simulations
Connecting Cores and Black Hole Dynamics across Scales: From Globular Clusters to Massive Ellipticals. The centers of massive elliptical galaxies exhibit a wide range in density profiles, from central cusps to resolved cores with order kiloparsec sizes. The cored ellipticals have been linked to the presence of supermassive black hole binaries that excavate their hosts' central stellar populations through three-body encounters. This connection between cores and black holes similarly operates in globular clusters, which also exhibit a bimodality in cored and core-collapsed architectures, rich and depleted, respectively, in stellar black holes. We report new estimates of the total black hole mass in 25 Galactic globular clusters based on a suite of roughly 150 Monte Carlo N-body simulations that fit observed surface brightness and velocity dispersion profiles. We show that both globular clusters and massive elliptical galaxies individually exhibit strong correlations between total black hole mass (M∙) and core radius (rc) and that these individual relations share a common power-law exponent to within 1σ statistical precision:  M∙∼rc1.3 . The individual relations appear to be offset, suggesting swarms of stellar black holes scour globular cluster cores more efficiently than lone supermassive black holes scour the cores of massive ellipticals. Yet the shared basis of core scouring via black hole binaries hints at a unified M∙─rc connection across over 10 orders of magnitude in M∙. Our findings imply core radius measurements may offer a powerful observational constraint on black hole merger rates, from kilohertz sources detectable by LIGO/Virgo/KAGRA formed in globular clusters to millihertz and nanohertz sources formed in massive elliptical galaxies.

Keywords: Globular star clusters, Stellar dynamics, Gravitational waves, N-body simulations, Astrophysical black holes
A 50 minute Coronal Kink Oscillation and Its Possible Photospheric Counterpart. A coronal loop of 290 Mm length, observed at 171 Å with Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly on 2024 February 6 near active region 13571, is found to oscillate with two significantly different oscillation periods, 48.8 ± 6.1 and 4.8 ± 0.3 minutes. The oscillations occur in the time intervals without detected flares or eruptions. Simultaneously, near the northern footpoint of the oscillating loop, we detect a 49.6 ± 5.0 minute periodic variation of the average projected photospheric magnetic field observed with SDO/Helioseismic and Magnetic Imager. The shorter-period decayless oscillation is attributed to the eigenmode, standing kink oscillation of the loop, while the longer-period oscillation may be the oscillatory motion caused by the periodic footpoint driver. The photospheric long-period process can also drive the short-period, eigen oscillation of the loop via the self-oscillatory "violin" mechanism, in which a transverse oscillation is excited by an external quasi-steady flow. This finding indicates that the most powerful, lower-frequency spectral components of photospheric motions, which are well below the Alfvénic/kink cutoff, can reach the corona.

Keywords: Solar active region magnetic fields, Solar photosphere, Solar coronal loops, Solar coronal waves, Solar corona
Water-driven Accessible Potential Karstic Caves in Hebrus Valles, Mars: Implications for Subsurface Habitability. The Hebrus Valles region on Mars exhibits geomorphological indicators of past aqueous activity, such as fluvial channels and aligned sinkholes. While Martian skylights have mostly been linked to volcanic or tectonic origins, caves formed by water-mediated dissolution remain unexplored. This study investigates eight skylight features in Hebrus Valles as the first potential karstic cave candidates on Mars. We evaluate whether these features are indicative of collapse entrances formed through dissolution of carbonate- and sulfate-rich lithologies. To this end, the investigation is carried out by integrating mineralogical maps from the Thermal Emission Spectrometer (TES), hydrogen data from the Gamma Ray Spectrometer (GRS), and TES-derived thermal inertia and dust index maps. 3D structural modeling was performed using High Resolution Imaging Science Experiment (HiRISE)─derived Digital Terrain Models. Morphological assessments were conducted using Context Camera and HiRISE images. The skylights exhibit morphologies consistent with subsurface dissolutional collapse. TES data reveal enrichment in carbonates and sulfates near the skylights, and GRS data show elevated water-equivalent hydrogen. The skylights lie within indurated, low-dust terrains and are spatially associated with fluvial features. A 3D reconstruction from morphological data of cavity geometry is consistent with its being karstic.

Keywords: Planetary surfaces, Martian satellites, Surface processes, Surface composition, Planetary mineralogy
The Redshift Distribution of Einstein Probe Transients Supports Their Relation to Gamma-Ray Bursts. The launch of the Einstein Probe unleashed a new era of high-energy transient discovery in the largely unexplored soft X-ray band. The Einstein Probe has detected a significant number of fast X-ray transients that display no gamma-ray emission, complicating their robust association with more common gamma-ray bursts. To explore their possible connection, we analyzed the redshift distribution of both Einstein Probe fast X-ray transients and long-duration gamma-ray bursts. A comparative analysis of their cumulative redshift distributions using nonparametric two-sample tests, namely the Kolmogorov─Smirnov and Anderson─Darling tests, finds no statistically significant difference. These tests favor that their redshifts are drawn from the same underlying distribution. This empirical connection between Einstein Probe transients and long gamma-ray bursts is further supported by their agreement with the so-called "Amati relation" between the spectral peak energy and the isotropic-equivalent energy. Together, these results indicate that most extragalactic Einstein Probe fast X-ray transients are closely related to long gamma-ray bursts and originate from a massive star (collapsar) progenitor channel. Our findings highlight the role of the Einstein Probe in uncovering the missing population of failed jets and dirty fireballs that emit primarily at soft X-ray wavelengths.

Keywords: X-ray astronomy, X-ray transient sources, Gamma-ray bursts
Orbital Characterization of a Newly Discovered Small Satellite around Quaoar. Recent observations of a stellar occultation have revealed the presence of a previously undiscovered small satellite around Quaoar. Orbiting near Quaoar's unusual ring system, this new satellite has the potential to provide significant insights into the formation and evolution of Quaoar and its ring system. In this Letter, we characterize the orbit of this newly discovered satellite, finding that it is likely on a  3.6−0.3+0.5  day orbit, plausibly placing it near a 5:3 mean motion resonance with Quaoar's outermost known ring. Examining the possibility of observing the newly discovered satellite with further stellar occultations, we estimate that ∼hundreds of observing stations are required for recovery, since phase information about its orbit was rapidly lost after the lone detection. We also attempted to recover the satellite in JWST NIRCam imaging of Quaoar, but find no convincing detection. This nondetection is limited by the accuracy of the available NIRCam point-spread function models, as well as the satellite's extreme faintness and close-in orbital separation. Therefore, current-generation telescopes will likely struggle to directly image this new satellite, but near-future 30 m class telescopes should prove capable of detecting it. Discovery of such a satellite provides evidence that the rings around Quaoar may have been part of an initially broad collisional disk that has evolved considerably since its formation. To further explore this hypothesis, we encourage follow-up observations of the rings and satellites with stellar occultations and direct imaging, as well as updated hydrodynamical, collisional, and tidal modeling of the system.

Keywords: Shepherd satellites, Dwarf planets, Stellar occultation, Trans-Neptunian objects
The Photochemical Plausibility of Warm Exo-Titans Orbiting M Dwarf Stars. The James Webb Space Telescope (JWST) has begun to spectrally characterize small exoplanets orbiting M dwarf stars, but interpretation of these spectra is ambiguous, with stellar, instrumental, or atmospheric origins possible for apparent spectral features. Consequently, the interpretation of JWST small exoplanet spectra follows a Bayesian approach, with less theoretically plausible interpretations facing a higher burden of proof. Here, we use photochemical modeling to evaluate the plausibility of warm exo-Titans, exoplanets with N2─CH4 atmospheres analogous to Titan but orbiting closer to their host stars. Consideration of warm exo-Titans is motivated by arguments from planet formation, as well as tentative evidence from observations. Using TRAPPIST-1e as a case study, we show that the higher instellation experienced by warm exo-Titans reduces their CH4 lifetime  τCH4  relative to true Titan by orders of magnitude, reducing the probability of observing them. We constrain the  τCH4  on a warm exo-Titan to be ≤0.1× (and most likely ≤0.02×) true Titan, implying the absolute probability of detecting a warm exo-Titan is &lt;0.1 and likely &lt;0.01. This finding is consistent with recent JWST nondetections of CH4-dominated atmospheres on warm terrestrial exoplanets. The low prior probability means that the standard of proof required to claim a warm exo-Titan detection is high, and we offer specific suggestions toward such a standard of proof. Observation of oxidized carbon species would corroborate a putative warm exo-Titan detection. Confirmed detection of warm exo-Titans would signal the need to fundamentally rethink our understanding of the structure, dynamics, and photochemistry of Titan-like worlds.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Theoretical models, Methane, Ocean planets, Titan, James Webb Space Telescope
Unusually High Gas-to-dust Ratios Observed in High-redshift Quiescent Galaxies. Tracking the cold molecular gas contents of galaxies is critical to understand the interplay between star formation and galaxy growth across cosmic time. Observations of the long-wavelength dust continuum, a proxy for the cold gas, are widely used in the high-redshift community because of their ease and efficiency. These measurements rely on the assumption of a molecular gas-to-dust mass ratio, typically taken to be δGDR ≍ 100 in massive, metal-rich systems. We present Atacama Large Millimeter/submillimeter Array observations of the 870 μm dust continuum in a sample of five massive quiescent galaxies at z ∼ 1 with existing detections of CO(2─1). We find surprisingly weak dust emission, falling a factor of ≳0.4─0.8 dex below the typical correlation between CO and continuum luminosity. We interpret this dust deficiency as evidence for unusually high δGDR in these galaxies, which we calculate to range from 300 to at least 1200. Our results and other observations from the literature are generally compatible with predictions from the SIMBA cosmological simulation that dust is preferentially destroyed in quiescent galaxies. Ultimately, we conclude that the dust continuum is a highly unreliable tracer of the molecular gas in high-redshift quiescent galaxies. As a consequence, we may know much less about the cold gas contents of this population than previously thought.

Keywords: Galaxy quenching, Molecular gas, Dust continuum emission, Galaxy evolution
XRISM Resolves Relativistic Effects from the Innermost Accretion Disk in Serpens X-1. We present the first XRISM/Resolve observation of the persistently accreting neutron star (NS) low-mass X-ray binary Serpens X-1. The source was observed on 2024 October 17, for approximately 350 ks of elapsed time, resulting in 171 ks of exposure. The source exhibited 22% variability with respect to the average count rate of 73.1 counts s−1 during the observation, but remained in a spectrally soft state throughout. The time averaged spectrum was analyzed in conjunction with spectra extracted from periods of different count rates to check for variations in spectral components. The unprecedented energy resolution of 4.5 eV at 6 keV of XRISM/Resolve provides a detailed look at the shape and structure of the Fe emission line within the data, which shows a dual-peaked structure with an extended red wing, and a steep decline in the blue wing of the line profile. Fits with the reflection model RELXILLNS are able to describe the structure in the Fe line region, and confirm previous results that the disk is close to the NS (Rin =  1.02−0.01+0.21 RISCO). These models also measure a low systemic inclination (i = 5° ± 1°), confirming prior X-ray and optical studies. Alternative models were explored to describe the structure of the Fe line profile; however, relativistic reflection provides the simplest and statistically best explanation of the data.

Keywords: Accretion, Neutron stars, Low-mass x-ray binary stars
A Quest for Sulfur-bearing Refractory Species: Identification of CaS in the Interstellar Medium. The recent detection of refractory molecules in massive star-forming regions provides a means of probing the innermost regions of disks around massive stars. These detections also make it possible to explore the chemical composition of refractories through gas-phase observations. In this regard, identifying refractory compounds containing sulfur could reveal potential connections between sulfur and refractories, as well as help determine the sulfur budget in these extreme environments. We find convincing evidence of a reliable detection of CaS, and tentative detections of KS and KSH, in the disk G351.77-mm1. These are the first ever identifications of these species in the interstellar medium. The CaS, KS, and KSH column densities are about 3 orders of magnitude lower than those of the abundant sulfur compounds SO2, CH3SH, and SiS, proving that these species are not the major reservoir of sulfur at the spatial scales probed by our observations. Higher angular resolution observations at different wavelengths are required to confirm these detections, which are of paramount importance to gain insights into the formation of gas-phase refractory molecules.

Keywords: Interstellar molecules, Spectral line identification, Star forming regions, Chemical abundances, Astrochemistry
Quasi-thermal Noise in the Heliosphere, Including the Electron, Proton, and Shot Noise. The total noise spectrum in the frequency band near the plasma frequency fp plays an important role in plasma and radio wave detections in the solar wind. The noise comes from the electron and proton quasi-thermal noise (QTN) and the shot noise, and their radial distributions in the heliosphere are investigated based on plasma measurements from several spacecraft. Power spectral profiles of the generic total noise are calculated at different heliocentric radial distances, and the separate contributions from the three noises with different antenna lengths are then given. Our results show that one could perform QTN diagnostics of plasma density and temperature within a wider range of heliocentric distance if a longer antenna were to be used. The influence of model parameters—especially the drift velocity of the solar wind—on the QTN spectrum is further discussed. In general, a larger density and higher temperature causes a more significant proton QTN, while the drift velocity directly leads to the Doppler shift effect on the noise spectrum. A new approximation is proposed to estimate the profile of the electron QTN with considerable drift velocity, but it should be treated cautiously in practical situations, because of the rough simplification and inevitable overestimation of the shift. This work may provide a reference for future deep-space explorations in the whole heliosphere and also for the design of antenna systems.

Keywords: Space plasmas, Solar wind, Interplanetary physics
Polar Filaments Capture High-latitude Solar Poloidal Field Interactions and Can Foretell the Future Sunspot Cycle Amplitude before Polar Field Precursors. Polar fields at the minimum of a sunspot cycle—which are a manifestation of the radial component of the Sun's poloidal field—are deemed to be the best indicator of the strength of the toroidal component and hence, the amplitude of the future sunspot cycle. However, the Sun's polar magnetic fields are difficult to constrain with ground-based or space-based observations from near the plane of ecliptic. In this context, polar filaments—dark, elongated structures that overlie polarity inversion lines—are known to offer critical insights into solar polar field dynamics. Through investigations of the long-term evolution of polar filament areas and length acquired from the Meudon Observatory and complimentary solar surface flux transport simulations, here, we establish the common physical foundation connecting the Babcock─Leighton solar dynamo mechanism of solar polar field reversal and buildup with the origin and evolution of polar filaments. We discover a new relationship connecting the residual filament area of adjacent solar cycles with the amplitude of the next sunspot cycle—which can serve as a new tool for solar cycle forecasts—advancing the forecast window to earlier than polar-field-based precursors. We conclude that polar filament properties encapsulate the physics of interaction of the poloidal magnetic field of the previous and current sunspot cycles, the result of which is the net poloidal magnetic field at the end of the current cycle, thus encoding as a precursor the strength of the upcoming solar cycle.

Keywords: Solar cycle, The Sun, Solar filaments, Solar magnetic fields
Supergranulation and Poleward Migration of the Magnetic Field at High Latitudes of the Sun. Magnetoconvection at the solar surface governs the dynamics in the upper solar atmosphere and sustains the heliosphere. Properties of this fundamental process are poorly described near the solar poles. Here we report the first out-of-ecliptic remote-sensing observations of the south pole of the Sun from a high-latitude campaign of the Solar Orbiter spacecraft, which reveal spatial and temporal evolution of supergranular convective cells. The supergranular cells have spatial scales of 20─40 Mm. From 8 days of observations starting on 2025 March 16, our analysis shows that the magnetic network migrates poleward, on average, at high latitudes (above 60°), with speeds in the range of 10─20 m s−1, depending on the structures being tracked. These results shed light on the buildup of the polar magnetic field that is central to our understanding of the solar cycle and the heliospheric magnetic field.

Keywords: Solar chromosphere, Supergranulation, Solar magnetic fields, Solar meridional circulation