Sazuna/UAT_keywords huggingface dataset:
Impact-induced Vaporization during Accretion of Planetary Bodies. Giant impacts dominate the late stages of accretion of rocky planets. They contribute to the heating, melting, and sometimes vaporizing of the bodies involved in the impacts. Due to fractionation during melting and vaporization, planet-building impacts can significantly change the composition and geochemical signatures of rocky objects. Using first-principles molecular dynamics simulations, we analyze the shock behavior of complex realistic silicate systems, representative of both rocky bodies. We introduce a novel criterion for vapor formation that uses entropy calculations to determine the minimum impact velocity required to pass the threshold for vapor production. We derive impact velocity criteria for vapor formation—7.1 km s‑1 for chondritic bodies—and show that this threshold is reached in 61% and 89% of impacts in dynamical simulations of the late stages of accretion with classical and annulus starting configuration (respectively) for analogs of Earth. These outcomes should be nuanced by factors such as the impact angle and the mass of the impacting bodies, which further influence the vaporization dynamics and the resultant material distribution. Our findings indicate that vaporization was common during accretion and likely played a crucial role in shaping the early environments and material properties of terrestrial planets.

Keywords: Impact phenomena, Solar system formation, Carbonaceous chondrites, Mineral physics, Planetesimals, Planet formation
Episodic X-Ray Outflows from the Tidal Disruption Event ASASSN-14li. ASASSN-14li is a low-redshift (z = 0.0206) tidal disruption event (TDE) that has been studied extensively across the entire electromagnetic spectrum and has provided one of the most sensitive measurements of a TDE to date. Its X-ray spectrum is soft and thermal (kT ∼ 0.05 keV) and shows a residual broad absorption feature between 0.6 and 0.8 keV, which can be associated with a blueshifted O VII line (rest-frame energy 0.57 keV) resulting from an ultrafast outflow at early times (within 40 days of optical discovery). By carefully accounting for photon pileup and using XSTAR photoionization models tailored to the evolving disk continuum properties, we analyze the entire archival X-ray data from XMM-Newton and track the evolution of this absorption feature for ∼4.5 yr post-disruption. Our main finding is that the absorption feature is transient and intermittent. Assuming the same underlying physical model (i.e., outflows) for the recurring absorption feature in ASASSN-14li, the outflow is seen to disappear and reappear multiple times during the first ∼1.5 yr of its evolution. No observable spectral imprint is detected thereafter. While theoretical studies suggest the launch of outflows in the early phases of the outburst during the super-Eddington regime, the outflow's intermittent behavior for multiple years after disruption is unusual. We discuss this peculiar behavior within the context of varying inner-disk truncation, radiation pressure, and magnetically driven outflow scenarios.

Keywords: Accretion, Black hole physics, Tidal disruption
Is the Spin of the Black Hole in GX 339–4 Negative?. We have studied the accreting black hole binary GX 339–4 using two highly accurate broadband X-ray data sets in very soft spectral states from simultaneous NICER and NuSTAR observations. Joint fitting of both data sets with relativistic models of the disk and its Comptonization and reflection allows us to relatively accurately determine the black hole mass, spin, distance, and inclination. However, we find that the measured values strongly depend on the used disk model. With widely used Kerr disk models treating departures from local blackbody spectra using color corrections, we find relatively low black hole masses and strongly negative spins (i.e., retrograde accretion). Then, models employing radiative transfer calculations of the disk atmosphere predict moderately positive spins and high masses. When adding a warm corona above the disk (as proposed before for both active galactic nuclei and accreting binaries), we find that the spin is weakly constrained but consistent with zero. In all cases, the fitted inclination is low, ≈30°–34°. For the spin axis aligned with the binary axis, the mass function for this source implies large values of the mass, consistent only with those obtained with either disk-atmosphere models or the presence of a warm corona. We also test different disk models for an assumed set of mass, distance, and inclination. We find that different models yield values of the spin parameter differing by up to ∼0.3. Our results confirm previously found strong model dependencies of the measured black hole spin, now by comparing different disk models and for a low-mass X-ray binary.

Keywords: Accretion, X-ray binary stars, Rotating black holes, X-ray sources, Astrophysical black holes
Using Detailed Single-star and Binary-evolution Models to Probe the Large Observed Luminosity Spread of Red Supergiants in Young Open Star Clusters. Red supergiants (RSGs) represent a late evolutionary stage of massive stars. Recent observations reveal that the observed luminosity range of RSGs in young open clusters is wider than expected from single-star evolution models. Binary evolution effects have been suggested as a possible explanation. Here, we analyze 3670 detailed binary-evolution models, as well as corresponding single-star models, to probe the contribution of binary mass transfer and binary mergers to the luminosity distribution of RSGs in star clusters with ages up to 100 Myr. We confirm that the expected luminosity range of RSGs in a coeval population can span a factor of 10, as a consequence of mergers between two main-sequence stars, which reproduces the observed RSG luminosity ranges in rich clusters well. While the luminosity increase as consequence of mass transfer is more limited, it may help to increase the number of overluminous RSGs. However, our results also demonstrate that binary effects alone are insufficient to account for the number of RSGs found with luminosities of up to 3 times those predicted by current single-star models. We discuss observational accuracy, rotational mixing, age spread, and intrinsic RSG variability as possible explanations. Further observations of RSGs in young open clusters, in particular studies of their intrinsic brightness variability, appear crucial for disentangling these effects.

Keywords: Binary stars, Red supergiant stars, Massive stars, Young star clusters, Stellar evolutionary models, Red straggler stars, Stellar evolution
Electrodynamics and Dissipation in the Binary Magnetosphere of Premerger Neutron Stars. We investigate the energy release in the interacting magnetospheres of binary neutron stars (BNSs) with global 3D force-free electrodynamics simulations. The system dynamics depend on the inclinations χ1 and χ2 of the stars' magnetic dipole moments relative to their orbital angular momentum. The simplest aligned configuration (χ1 = χ2 = 0∘) has no magnetic field lines connecting the two stars. Remarkably, it still develops separatrix current sheets warping around each star and a dissipative region at the interface of the two magnetospheres. A Kelvin–Helmholtz (KH)–type instability drives significant dissipation at the magnetospheric interface, generating local Alfvénic turbulence and escaping fast magnetosonic waves. Binaries with inclined magnetospheres release energy in two ways: via KH instability at the interface and via magnetic reconnection flares in the twisted flux bundles connecting the companions. Outgoing compressive waves occur in a broad range of BNS parameters, possibly developing shocks and sourcing fast radio bursts. We discuss implications for X-ray and radio precursors of BNS mergers.

Keywords: Plasma astrophysics, Radiative processes, Magnetic fields, Binary pulsars, Magnetohydrodynamical simulations
High-frequency Power Spectrum of Active Galactic Nucleus NGC 4051 Revealed by NICER. Variability studies offer a compelling glimpse into black hole dynamics, and Neutron Star Interior Composition Explorer's (NICER's) remarkable temporal resolution propels us even further. NICER observations of an active galactic nucleus (AGN), NGC 4051, have charted the geometry of the emission region of the central supermassive black hole. Our investigation of X-ray variability in NGC 4051 has detected extreme variations spanning a factor of 40–50 over a mere 10–12 hr. For the first time, we have constrained the X-ray power spectral density (PSD) of the source to 0.1 Hz, corresponding to a temporal frequency of 104 Hz in a galactic X-ray binary with a mass of 10 M⊙. No extra high-frequency break/bend or any quasiperiodic oscillations are found. Through detailed analysis of energy-dependent PSDs, we found that the PSD normalization, the high-frequency PSD slope, as well as the bending frequency remain consistent across all energies within the 0.3–3 keV band, revealing the presence of a constant temperature corona. These significant findings impose critical constraints on current models of X-ray emission and variability in AGN.

Keywords: Seyfert galaxies, Active galactic nuclei, Time domain astronomy, High energy astrophysics
Near- and Mid-ultraviolet Observations of X-6.3 Flare on 2024 February 22 Recorded by the Solar Ultraviolet Imaging Telescope on board Aditya-L1. Solar flares are regularly observed in extreme-ultraviolet soft X-rays (SXRs) and hard X-rays (HXRs). However, those in near- and mid-ultraviolet are sparse. The Solar Ultraviolet Imaging Telescope (SUIT) on board the Aditya-L1, launched on 2023 September 2, provides regular observations in the 200–400 nm wavelength range through 11 filters. Here, we report the observation of the X6.3 flare on 2024 February 22 using eight narrowband (NB) filters of SUIT. We have also used co-spatiotemporal observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), Solar Orbiter/STIX, GONG Hα, Aditya-L1/SoLEXS, and GOES. We obtained light curves over the flaring region from AIA 1600 and 1700 Å and GONG Hα and compared them with the disk-integrated light curve obtained from GOES and SoLEXS SXRs and STIX HXRs. We find that the flare peaks in SUIT NB01, NB03, NB04, and NB08 filters simultaneously with HXRs 1600 and 1700 Å, along with the peak temperature obtained from SoLEXS. In contrast, in NB02 and NB05, the flare peaks ∼2 min later than the HXR peak, while in NB06 and NB07, the flare peaks ∼3 min after the GOES SXR peak. To the best of our knowledge, this is the first observation of a flare in these wavelengths (except in NB03, NB04, and NB05). Moreover, for the first time, we show the presence of a bright kernel in NB02. These results demonstrate the capabilities of SUIT observations in flare studies.

Keywords: Solar atmosphere, Solar flares, Solar photosphere, Solar flare spectra, Solar active regions, Eruptive phenomena, Solar physics, Active solar chromosphere
Fading Light, Fierce Winds: JWST Snapshot of a Sub-Eddington Quasar at Cosmic Dawn. The majority of most luminous quasars during the epoch of reionization accrete near or above the Eddington limit, marking the vigorous growth of primitive supermassive black holes (SMBHs). However, their subsequent evolution and environmental impact remain poorly characterized. We present JWST/NIRSpec prism integral field unit observations of HSC J2239+0207, a low-luminosity quasar at z ∼ 6.25 likely in a late stage of mass assembly with an overmassive SMBH relative to its host galaxy. Using Hβ and Hα broad emission lines, we estimate an SMBH mass MBH ∼ 3 × 108 M⊙ and confirm its sub-Eddington accretion at λEdd ∼ 0.4. Strong Fe II emission and a proximity zone of typical size suggest a metal-rich, highly evolved system. In the far-UV, this quasar presents strong broad absorption line features, indicative of high-velocity winds (ν ∼ 104 km s‑1). Meanwhile, minimal dust reddening is inferred from the quasar continuum and broad-line Balmer decrement, suggesting little dust along the polar direction. Most interestingly, we identify a gas companion ∼5 kpc from the quasar with a high [O III]/Hβ ratio (≳10), likely representing outflowing gas blown away by active galactic nucleus (AGN) feedback. These results highlight HSC J2239+0207 as a likely fading quasar in transition, providing rare insights into SMBH evolution, AGN feedback, and AGN–galaxy interactions in the early Universe.

Keywords: AGN host galaxies, Broad-absorption line quasar, Quasars, James Webb Space Telescope, Galaxy evolution, Reionization
The JWST Weather Report from the Isolated Exoplanet Analog SIMP 0136+0933: Pressure-dependent Variability Driven by Multiple Mechanisms. Isolated planetary-mass objects share their mass range with planets but do not orbit a star. They lack the necessary mass to support fusion in their cores and thermally radiate their heat from formation as they cool, primarily at infrared wavelengths. Many isolated planetary-mass objects show variations in their infrared brightness consistent with nonuniform atmospheric features modulated by their rotation. SIMP J013656.5+093347.3 is a rapidly rotating isolated planetary-mass object, and previous infrared monitoring suggests complex atmospheric features rotating in and out of view. The physical nature of these features is not well understood, with clouds, temperature variations, thermochemical instabilities, and infrared-emitting aurora all proposed as contributing mechanisms. Here we report JWST time-resolved low-resolution spectroscopy from 0.8 to 11 μm of SIMP J013656.5+093347.3, which supports the presence of three specific features in the atmosphere: clouds, hot spots, and changing carbon chemistry. We show that no single mechanism can explain the variations in the time-resolved spectra. When combined with previous studies of this object indicating patchy clouds and aurorae, these measurements reveal the rich complexity of the atmosphere of SIMP J013656.5+093347.3. Gas giant planets in the solar system, specifically Jupiter and Saturn, also have multiple cloud layers and high-altitude hot spots, suggesting these phenomena are also present in worlds both within and beyond our solar system.

Keywords: Brown dwarfs, Exoplanet atmospheric variability, Exoplanet atmospheric structure, Stellar atmospheres, Exoplanet atmospheres, T dwarfs
Orbital Inclination of Astrometric Binaries and the Dearth of Face-on Orbits in Gaia DR3 Solutions. The orbital solutions for astrometric (unresolved) binary stars provided in the Gaia mission DR3 reveal an obvious deficit of face-on orbits with line-of-sight inclinations close to 0 or π. This is shown to be an intrinsic mathematical feature of the orbit estimation technique involving the intermediate Thiele-Innes parameters, which are transformed to the Campbell geometric parameters. A direct condition equation defining the inclination angle via the Thiele-Innes values independently of the other orbital elements is used to investigate the origin of this near-degeneracy for face-on orbits. The emerging bias and correlation of inclination and semimajor axis are illustrated using Monte Carlo simulations for two specific template configurations representing face-on and edge-on orbits. The results have significant impact on the interpretation and follow-up confirmation of Gaia-detected binary systems, including candidate exoplanets and brown dwarf companions.

Keywords: Substellar companion stars, Orbital elements, Astrometric binary stars, Gaia, Orbit determination
Newest Measurements of Cosmic Curvature with BOSS/eBOSS and DESI DR1 Baryon Acoustic Oscillation Observations. Determining the cosmic curvature (ΩK) independent of cosmological models plays a key role in revealing the background physics of our Universe. In this Letter, we propose an improved method to measure the cosmic curvature using the observations of baryon acoustic oscillations (BAO). It is important to highlight that our method circumvents the influence induced by the Hubble constant (H0) and the sound horizon (rd) in BAO observations. We use the newest BAO observations from Baryon Oscillation Spectroscopic Survey (BOSS)/Extended Baryon Oscillation Spectroscopic Survey (eBOSS) and Dark Energy Spectroscopic Instrument (DESI) surveys. By taking into account the information of cosmic chronometers reconstructed from two machine learning methods (Gaussian process and artificial neural network), we demonstrate that one can achieve constraint on the cosmic curvature with ∣ΩK∣ &lt; 0.04 and ∣ΩK∣ &lt; 0.01. Further comparative analysis of the BOSS/eBOSS and DESI DR1 observations indicates that there is almost no difference between the two BAO samples at the current observational level. Therefore, our results confirm that the newest BAO observations provide a cosmological model–independent tool to verify the flatness of the Universe.

Keywords: Observational cosmology, Cosmological parameters
Constraints on the Fractional Changes of the Fundamental Constants at a Look-back Time of 2.5 Myr. The quantum nature of gravity remains one of the greatest mysteries of modern physics, with many unified theories predicting variations in fundamental constants across space and time. Here we present precise measurements of these variations at galactic dynamical timescales—a critical but previously unexplored regime. Using simultaneous observations of H I and OH lines in M31, we probe potential variations of fundamental constants at a look-back time of 2.5 million yr. We obtained  , with complementary constraints on Δ(μα2)/(μα2) &lt; 4.6 × 10‑3, and Δgp/gp &lt; 7.2 × 10‑3, where α is the fine structure constant, μ is the proton–electron mass ratio, and gp is the proton g-factor. These results bridge the gap between laboratory tests and cosmological observations, providing unique insights into the coupling between local dynamics and fundamental physics. Our findings challenge theories predicting significant variations over galactic timescales while demonstrating a powerful new probe of quantum gravity models.

Keywords: Atomic spectroscopy, Cosmological constant experiments, Molecular spectroscopy
Interpreting the Extremely Diffuse Stellar Distribution of the Nube Galaxy through Fuzzy Dark Matter. Recent observations have uncovered a remarkably flat and extremely diffuse stellar distribution within the almost dark dwarf galaxy Nube, posing a challenge to the standard cold dark matter scenario. In this study, we employ numerical simulations to explore the possibility that this anomalous stellar distribution can be attributed to the dynamical heating effect of fuzzy dark matter (FDM). The relatively isolated location and low baryon fraction of Nube make it an ideal system for investigating this effect. Our findings indicate that by adopting a halo profile consistent with the dynamical mass estimation of Nube and an FDM particle mass on the order of 10‑23 eV, the final 2D stellar distribution derived from simulation closely matches observational data. These results suggest that FDM could provide an explanation for the extremely diffuse stellar distribution of Nube.

Keywords: Galaxy dark matter halos, Dark matter, Low surface brightness galaxies
Measuring the Mean Free Path of H I Ionizing Photons at 3.2 ≤ z ≤ 4.6 with DESI Y1 Quasars. The mean free path of ionizing photons in the intergalactic medium (IGM;  ) is a crucial quantity in modeling the ionization state of the IGM and the extragalactic ultraviolet background, and it is widely used in hydrodynamical simulations of galaxies and reionization. We construct the largest quasar spectrum data set to date—12,595 signal-to-noise ratio &gt; 3 spectra—using the Y1 observations of the Dark Energy Spectroscopic Instrument, to make the most precise model-independent measurement of the mean free path at 3.2 ≤ z ≤ 4.6. By stacking the spectra in 17 redshift bins and modeling the Lyman-continuum profile, we get a redshift evolution   at 2 ≤ z ≤ 5, which is much shallower than the previous estimate,  . We then explore the sources of systematic bias, including the choice of the intrinsic quasar continuum, the consideration of Lyman-series opacity and Lyman-limit opacity evolution, and the definition of  . Combining our results with estimates of   at higher redshifts, we conclude at high confidence that the evolution in   steepens at z ≈ 5. We interpret this inflection as the transition from the end of H I reionization to a fully ionized plasma that characterizes the IGM of the past ∼10 billion yr.

Keywords: Reionization, Observational cosmology, Quasar absorption line spectroscopy, Intergalactic medium
In Situ Formation of Star Clusters at z &gt; 7 via Galactic Disk Fragmentation: Shedding Light on Ultracompact Clusters and Overmassive Black Holes Seen by JWST. We investigate the nature of star formation in gas-rich galaxies at z &gt; 7 forming in a markedly overdense region, in the vicinity of a massive virialized halo already exceeding 1012 M⊙, through the use of the very-high-resolution cosmological hydrodynamical simulation MassiveBlackPS with a spatial resolution of 2 pc. We find that not only the primary galaxy but also the lower-mass companion galaxies rapidly develop massive self-gravitating compact gas disks, less than 500 pc in size, which undergo fragmentation by gravitational instability into very massive bound clumps. Star formation proceeds fast in the clumps, which quickly turn into compact star clusters with masses in the range 105–108 M⊙ and typical half-mass radii of a few parsec, reaching characteristic densities above 105 M⊙ pc‑2. The properties of the clusters in the lowest-mass galaxy bear a striking resemblance to those recently discovered by the James Webb Space Telescope (JWST) in the lensed Cosmic Gems arc system at z = 10.2. We argue that, due to their extremely high stellar densities, intermediate-mass black holes would form rapidly inside the clusters, which would then swiftly sink and merge on their way to the galactic nucleus, easily growing into a 107 M⊙ supermassive black hole (SMBH). Due to the high fractional mass contribution of clusters to the stellar mass of the galaxies, in the range 20%–40%, the central SMBH would comprise more than 10% of the mass of its host galaxy, naturally explaining the overmassive SMBHs discovered by JWST at z &gt; 6.

Keywords: Galaxy formation, Star formation, Astrophysical black holes, Star clusters
PSR J1922+37: a 1.9 s Pulsar Discovered in the Direction of the Old Open Cluster NGC 6791. More than 300 pulsars have been discovered in Galactic globular clusters; however, none have been found in open clusters. Here we present results from a 20 hr survey of seven open clusters with the Five-hundred-meter Aperture Spherical radio Telescope. Our first discovery is a 1.9 s pulsar (J1922+37) found in the direction of the old open cluster NGC 6791. The measured dispersion measure (DM) implies a distance of 4.79 and 8.92 kpc based on the NE2001 and YMW16 electron density models, respectively. Given the large uncertainty of DM distance estimates, it is plausible that PSR J1922+37 is indeed a member of NGC 6791, for which the distance is 4.19 ± 0.02 kpc based on Gaia Data Release 3. If confirmed, PSR J1922+37 will be the first pulsar found in a Galactic open cluster. We outline future observations that can confirm this pulsar–open cluster association and discuss the importance of this pulsar for calibrating the characteristic ages of the pulsar population.

Keywords: Globular star clusters, Open star clusters, Radio pulsars