Sazuna/UAT_keywords huggingface dataset:
A Scaling Law for the Orbital Architecture of Planetary Systems Formed by Gravitational Scattering and Collisions. In the standard formation models of terrestrial planets in the solar system and close-in super-Earths in nonresonant orbits recently discovered by exoplanet observations, planets are formed by giant impacts of protoplanets or planetary embryos after the dispersal of protoplanetary disk gas in the final stage. This study aims to theoretically clarify a fundamental scaling law for the orbital architecture of planetary systems formed by giant impacts. In the giant impact stage, protoplanets gravitationally scatter and collide with one another to form planets. Using N-body simulations, we investigate the orbital architecture of planetary systems formed from protoplanet systems by giant impacts. As the orbital architecture parameters, we focus on the mean orbital separation between two adjacent planets and the mean orbital eccentricity of planets in a planetary system. We find that the orbital architecture is determined by the ratio of the two-body surface escape velocity of planets vesc to the Keplerian circular velocity vK, k = vesc/vK. The mean orbital separation and eccentricity are about 2ka and 0.3k, respectively, where a is the system semimajor axis. With this scaling, the orbital architecture parameters of planetary systems are nearly independent of their total mass and semimajor axis.

Keywords: Super Earths, Solar system terrestrial planets, Planet formation
Water Production Rates of the Interstellar Object 3I/ATLAS. We report the detection of water activity in the third confirmed interstellar object, 3I/ATLAS, based on ultraviolet imaging with the Neil Gehrels Swift Observatory's Ultraviolet/Optical Telescope. Assuming a reddening of 29% between 3325.7 and 5437.8 Å, measurements on 2025 July 31–August 1 yielded a first, marginal detection of OH (A2Σ–X2Π) emission near 3085 Å, corresponding to a water production rate of (0.74 ± 0.50) × 1027 molecules s‑1. The subsequent visit on 2025 August 18–20 revealed a clear OH detection, implying a higher water production rate of (1.36 ± 0.35) × 1027 molecules s‑1 (40 kg s‑1) at a heliocentric distance of 2.90 au. This places 3I/ATLAS among the few comets with confirmed OH emission beyond 2.5 au, where water ice sublimation from the nucleus is typically inefficient. The inferred production rate at 2.9 au implies an active area of at least 7.8 km2, assuming equilibrium sublimation. This requires that over 8% of the surface is active, which is larger than activity levels observed in most solar system comets. Contemporaneous near-infrared spectroscopy indicated the presence of icy grains in the coma, which may serve as an extended source of water vapor.

Keywords: Comae, Near ultraviolet astronomy, Neutral coma gases, Interstellar objects, Interstellar medium, Comets
A Black Hole Is Born: 3D General-relativistic Magnetohydrodynamic Simulation of Black Hole Formation from Core Collapse. We present the first three-dimensional, fully general-relativistic magnetohydrodynamic (3D GRMHD) simulation of a black hole (BH) formed from the collapsed core of a massive star. The ability to self-consistently capture the birth of a compact remnant in 3D is crucial for modeling natal BH properties (including masses, spins, and kicks), which are of particular interest in the era of gravitational-wave astronomy. However, such simulations have remained elusive due to extreme computational challenges and demands. We employ the GPU-accelerated dynamical-spacetime GRMHD code GRaM-X to follow the collapse, core bounce, shock propagation, and eventual BH formation of a massive stellar progenitor in full 3D. We initialize our simulation by mapping a one-dimensional (1D) model of a star with a zero-age-main-sequence mass of 45M⊙ to 3D. We use the core rotation velocity expected from stellar evolution modeling and a relatively weak dipolar magnetic field. The collapsing core drives a shock that reaches a maximum radius of roughly 170 km before stalling and does not lead to a successful explosion. The protoneutron star accretes matter before collapsing to form a BH tBH ≈ 325 ms after core bounce. The time of BH formation and initial BH mass are remarkably similar to those obtained with GR1D, a 1D general-relativistic neutrino-hydrodynamics code, to which we compare our results. We track the horizon of the newborn BH after formation and calculate a steady kick velocity of  vkick≈72kms‑1  and a mass of MBH ≈ 2.62M⊙, which is still rising at the end of the simulation.

Keywords: Stellar mass black holes, Gravitational collapse, Relativistic fluid dynamics, Magnetohydrodynamical simulations
High-redshift Merger-induced Bar-like Galaxies in IllustrisTNG. Recent discoveries made with JWST observations include a significant number of barred galaxies at high redshift. Their origin remains unclear, and their presence seems difficult to reproduce in cosmological simulations of galaxy formation and evolution. In this Letter, I present four examples of high-redshift bars selected from a sample of bar-like galaxies studied previously using IllustrisTNG simulations. All the galaxies formed their bars at redshifts z &gt; 3 via mergers with smaller satellites, although one had its bar formed even earlier, at z &gt; 5. The bars were born long, with lengths on the order of 3 kpc, and grew in time. Three of the four galaxies were later accreted by clusters and underwent multiple interactions with their respective brightest cluster galaxies. Their bar strength was to some extent affected by these interactions, but all the galaxies preserved their bar-like shape until the present time. By the end of the evolution, all the galaxies lost their gas and stopped forming stars; they retained essentially no disk component and were no longer rotationally supported. The examples demonstrate that high-z bars do not evolve into present-day barred disk galaxies similar to the Milky Way but rather into S0s or ellipticals typically found in galaxy clusters.

Keywords: Galaxy clusters, Galaxy bars, Interacting galaxies, Galaxy mergers, High-redshift galaxies, Galaxies
Not So Dark, Not So Dense: An Alternative Explanation for the Lensing Subhalo in SDSS J0946+1006. Previous studies of the strong-lens system SDSS J0946+1006 have reported a dark matter subhalo with an unusually high central density, potentially challenging the standard cold dark matter (CDM) paradigm. However, most analyses have assumed the subhalo to be completely dark, neglecting the possibility that it may host a faint galaxy. In this work, we revisit the lensing analysis of SDSS J0946+1006, explicitly modelling the subhalo as a luminous satellite. Incorporating light from the perturber broadens the range of allowed subhalo properties, revealing solutions with significantly lower central densities that are consistent with CDM expectations. The inferred luminosity of the satellite also aligns with predictions from hydrodynamical simulations. While high-concentration subhalos remain allowed, they are no longer statistically preferred. The luminous subhalo model yields a better fit to the data, while also offering a more plausible explanation that is in line with theoretical expectations. We validate our methodology using mock data, demonstrating that neglecting subhalo light can lead to inferred mass distributions that are artificially compact.

Keywords: Galaxy dark matter halos, Strong gravitational lensing, Dwarf galaxies, Dark matter
Orbital Eccentricity and Spin─Orbit Misalignment Are Evidence that Neutron Star─Black Hole Mergers Form through Triple Star Evolution. There is growing evidence that a substantial fraction of the neutron star─black holes (NSBHs) detected through gravitational waves merge with nonzero eccentricity or large black hole spin─orbit misalignment. This is in tension with leading formation scenarios to date. Residual eccentricity rules out formation from isolated binary stars, while neutron star (NS) natal kicks and unequal masses of NSBHs inhibit efficient pairing in dense stellar environments. We report that all observed properties—NSBH merger rate, eccentricity, and spin─orbit misalignment—are explained by the high prevalence of massive stellar triples in the field. Modeling their evolution from the zero-age main sequence, we investigate NSBH mergers caused by gravitational perturbations from a tertiary companion. The NS formation decisively impacts the triple stability, preferentially leaving behind surviving NSBHs in compact triple architectures with mild hierarchies. The rich three-body dynamics of compact, unequal-mass triples enables mergers across a wide range of orbital parameters and provides a natural explanation for an abundance of residual eccentricity and spin─orbit misalignment. We infer a total NSBH merger rate of  RNSBH∼1 ─23 Gpc−3 yr−1 (within uncertainties on NS kicks) with a few 10% exhibiting residual eccentricity e20 &gt; 0.1 or large spin─orbit misalignment  cosθBH&lt;0 , consistent with current observations. The mergers closely track the cosmic star formation rate due to short delay times (∼10─100 Myr), include a substantial fraction of burst-like highly eccentric systems (e20 &gt; 0.9), and almost universally retain eccentricities e20 &gt; 10−3 detectable by next-generation detectors. If evidence for eccentric and misaligned events solidifies, our results suggest that triple dynamics is the dominant formation channel of gravitational-wave events from NSBH mergers.

Keywords: Neutron stars, Multiple stars, Black holes, Stellar mass black holes, Stellar dynamics, Gravitational wave astronomy, Stellar physics, Gravitational waves, Trinary stars, Stellar remnants, Astrophysical black holes, Stellar evolution
Coexistence of Decaying and Decayless Kink Oscillations in a Bundle of Coronal Loops Triggered by an X6.3 Solar Flare. We report the coexistence of decaying and decayless kink oscillations within a single bundle of coronal loops during the X6.3-class solar flare on 2024 February 22. Using coordinated observations from Geostationary Operational Environmental Satellite, Solar Dynamics Observatory/Atmospheric Imaging Assembly, Advanced Space-based Solar Observatory, and New Vacuum Solar Telescope, we analyze five flare-activated coronal loops (S1–S5) and identify distinct oscillation regimes in different segments. Time–distance and curve-fitting analyses of the five selected coronal loops reveal a broad range of oscillation amplitudes (1.1–7.1 Mm) and periods (119–630 s). In loop S2, decayless oscillations with a period of 274.6 ± 1.0 s and nearly constant amplitude are observed to coexist for a period of time with rapidly decaying oscillations of a similar period, 271.1 ± 1.7 s. The differential emission measure diagnostics indicate strong spatial variation in magnetic field strength, decreasing from 30 G near the flare core to 11 G in the peripheral loops. These variations in oscillation regimes and magnetic field strength imply that the local plasma environment strongly influences wave decaying processes. These results suggest that magnetic topology and local plasma conditions play a key role in modulating the wave decaying behavior.

Keywords: Solar coronal loops
Resolving Emission from Small Dust Grains in the Blue Compact Dwarf II Zw 40 with JWST. We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) and Mid-infrared Instrument integral field spectroscopy of the nearby blue compact dwarf II Zw 40, which has a low metallicity of 25% of solar. Leveraging the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec, we present robust detections of the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission on 20 pc scales. The strength of the Pfδ emission relative to the 3.3 PAH feature is significantly stronger than typical higher-metallicity star-forming galaxies. We find that 3.3 μm PAH emission is concentrated near the northern super star cluster and is cospatial with CO gas. A strong correlation exists between the 3.3/11.3 PAH ratio and radiation hardness probed by [Ne III]/[Ne II], providing evidence of photodestruction of PAH molecules in intense radiation environments. Our analysis shows that while the overall PAH fraction is lower in II Zw 40 than in higher-metallicity galaxies, the contribution of the 3.3 μm PAH feature to the total PAH emission is higher. We propose that the PAH size distribution is fundamentally shaped by two competing mechanisms in low-metallicity environments: photodestruction and inhibited growth. Additionally, the high radiation field intensity in II Zw 40 suggests that multiphoton heating of PAHs may be an important effect. As one of the first spatially resolved studies of aromatic emission in a low-metallicity environment, our spectroscopic results offer practical guidance for future observations of the 3.3 μm PAH feature in low-metallicity galaxies using JWST.

Keywords: Blue compact dwarf galaxies, Polycyclic aromatic hydrocarbons, Infrared spectroscopy, Interstellar medium
Ion-scale Turbulence and Energy Cascade Rate in the Solar Corona and Inner Heliosphere. Plasma turbulence cascading from MHD to kinetic scales in the heliospheric plasma is believed to play a key role in coronal heating and fast solar wind acceleration, but the properties of the turbulence remain poorly constrained by observations. Here we compare the ion-scale density fluctuation levels inferred from the properties of solar radio bursts with the magnetic field fluctuation levels obtained through in situ measurements in the inner heliosphere. We find that the observed magnetic and density fluctuation amplitudes are consistent with excitation by kinetic Alfvén waves (KAWs) and/or KAW structures over a broad range of distances from the Sun. We then use the radio diagnostics and the KAW scenario to deduce the radial variation of magnetic fluctuation amplitudes in regions close to the Sun where in situ measurements cannot be obtained. Further, we calculate the energy cascade rate (plasma heating rate) profile over a region that extends from the low corona (∼0.1 R⊙) into the heliosphere (out to ∼1 au), and compare it to the energy deposition rate required to drive the solar wind. The cascade rate agrees with the available in situ measurements and also provides predictions closer than ∼10 R⊙ where in situ approaches are not available. The results provide unique diagnostics of the ion-scale plasma turbulence amplitude and energy cascade rate spanning over 3 orders of magnitude in solar distance.

Keywords: Slow solar wind, Fast solar wind, Solar wind, Plasma astrophysics, Solar physics, Solar radio emission, Alfven waves, Solar magnetic fields, Solar corona
On the Universality of Energy Extraction from Black Hole Spacetimes. The launching of astrophysical jets provides the most compelling observational evidence for direct extraction of black hole (BH) spin energy via the Blandford–Znajek (BZ) mechanism. While it is known that spinning Kerr BHs within general relativity (GR) follow the BZ jet power relation, the nature of BH energy extraction in general theories of gravity has not been adequately addressed. This study performs the first comprehensive investigation of the BZ jet power relation by utilizing a generalized BH spacetime geometry that describes parametric deviations from the Kerr metric of GR yet recovers the Kerr metric in the limit where all deviation parameters vanish. Through performing and analyzing an extensive suite of three-dimensional covariant magnetohydrodynamics simulations of magnetized gas accretion onto these generalized BH spacetimes, we find that the BZ jet power relation still holds, in some instances yielding jet powers far in excess of what can be produced by even extremal Kerr BHs. It is shown that independent variation of the frame-dragging rate of the BH can enhance or suppress the effects of BH spin, and by extension, of frame-dragging. This variation greatly enhances or suppresses the observed jet power and underlying photon ring image asymmetry, introducing a previously unexplored yet important degeneracy in BH parameter inference. Finally, we show that sufficiently accurate measurements of the jet power, accretion rate, and photon ring properties from supermassive BHs can potentially break this degeneracy, highlighting the need of independent investigations of BH frame dragging from observations.

Keywords: Accretion, Relativistic jets, Active galactic nuclei, General relativity, Astrophysical black holes, Magnetohydrodynamical simulations
Detection of Diffuse Radio Emission inside the Supernova Remnant G338.3-0.0 Associated with the γ-Ray Source HESS J1640-465. We report the discovery of diffuse radio emission within SNR G338.3−0.0 using new MeerKAT observations at 816 MHz and 1.4 GHz. The radio emission spatially overlaps with the X-ray pulsar wind nebula (PWN) powered by PSR J1640−4631 and the GeV/TeV γ-ray source HESS J1640−465. The morphology of this radio emission is centrally peaked and its extent is well contained within the SNR shell. A lack of mid- and far-infrared counterparts and the absence of cataloged H II regions argue against a thermal origin, while the morphology and radial profile are suggestive of a PWN origin powered by PSR J1640−4631. Under this assumption, we use a one-zone, time-dependant model to reproduce the size and broadband (radio, X-ray, and γ-ray) spectral energy distribution of the PWN. The modeling and broadband properties of this PWN suggest it is currently interacting with the reverse shock within its host SNR. This evolutionary stage is associated with particles escaping the PWN and entering the interstellar medium, suggesting this object may be an important source of Galactic PeV e±.

Keywords: Neutron stars, Rotation powered pulsars, Millisecond pulsars, Gamma-ray sources, Pulsars, Supernova remnants, Pulsar wind nebulae, Radio astronomy
The First Day of a Type Ia Supernova from a Double-degenerate Binary. Supernovae in binary star systems involve a hydrodynamical interaction between the ejecta and a binary companion. This collision results in shock heating and a modified density structure for the ejecta, both of which affect the light curve. As highlighted by D. Kasen, these considerations are particularly relevant for Type Ia supernovae, as the companion is expected to be Roche-lobe filling at the time of the explosion. We simulate here the interaction between Type Ia supernova ejecta and a white dwarf donor using Athena++, finding the formation of a low-density wake extending to higher velocities than the unperturbed ejecta. Radiation hydrodynamics is then used to generate synthetic light curves for the first day after the explosion for a range of viewing angles. We find that the hot, high-velocity, shocked ejecta yield L &gt; 1040 erg s−1 over half the sky in the first few hours. The photosphere within the shock-heated ejecta cools and recedes in velocity space, partially obscuring it from view, as heating from radioactive nickel becomes increasingly important in driving the supernova's luminosity. By one day after the explosion, the luminosity measured by observers looking directly into the wake is dimmer than that of a normal Type Ia supernova by 15% due to the modified density structure.

Keywords: Transient sources, Type Ia supernovae, Radiative transfer, Hydrodynamics
The Potential of the SPHEREx Mission for Characterizing Polycyclic Aromatic Hydrocarbon 3.3 μm Emission in Nearby Galaxies. Together with gas, stars, and supermassive black holes, dust is crucial in stellar and galaxy evolution. Hence, understanding galaxies' dust properties across cosmic time is critical to studying their evolution. In addition to photometric constraints on the absorption of blue light and its reemission at infrared wavelengths, dust grain properties can be explored spectroscopically via polycyclic aromatic hydrocarbon (PAH) emission bands in the mid-IR. The new SPHEREx space telescope conducts an all-sky spectrophotometric survey of stars and galaxies at wavelengths of 0.75–5 μm, making it ideal for studying the widespread presence of the 3.3 μm PAH emission across galaxy populations out to z ∼ 0.4. In this paper, we simulated galaxy spectra to investigate SPHEREx's capability to study PAH emission in such galaxies. We find that for the all-sky survey the PAH 3.3 μm emission band flux can be measured to 30% accuracy at  log(M/M⊙)&gt;9.5  and star formation rate (SFR) &gt; 1 M⊙ yr‑1 at z = 0.1,  log(M/M⊙)&gt;10.5  and SFR &gt; 10 M⊙ yr‑1 at z = 0.2–0.3, and  log(M/M⊙)&gt;11  and SFR &gt; 100 M⊙ yr‑1 at z = 0.4. For deep SPHEREx fields, a factor of ∼10 deeper sensitivity limits can be reached. Overall, SPHEREx will enable the measurement of the 3.3 μm PAH band emission in several hundred thousand galaxies across the sky, providing a population study of the smallest dust grains ("nano grains") and radiation properties in massive galaxies in the nearby Universe.

Keywords: Dust composition, Polycyclic aromatic hydrocarbons, Interstellar medium, Galaxy spectroscopy, Telescopes
Spatiotemporal Low First Ionization Potential Abundance: A Catalyst for Coronal Condensation. Radiative losses play a critical role in the cooling of plasmas. When chromospheric plasma is sufficiently heated, it can flow into coronal loops, which subsequently cool down due to radiation. From observations, we infer that this cooling does not occur uniformly, often resulting in coronal condensations such as coronal rain. To date, coronal condensations have only been found in simulations of steadily heated loops, and never in impulsively heated ones. We implement spatiotemporally variable elemental abundances in a radiative hydrodynamic code. Flows, including chromospheric evaporation, directly cause a shift in the local elemental abundances, which then affects the local radiative loss rate. As a consequence, we find that incorporating spatiotemporal low first ionization potential elemental abundances into coronal loop simulations directly causes coronal condensations, which are otherwise absent in impulsively heated loop or flare models. We conclude that spatiotemporal variations in elemental abundances are a fundamental feature of the solar corona and are therefore necessary to accurately model radiation.

Keywords: Solar flares, Solar coronal loops, The Sun, Solar coronal heating, Solar abundances
PSR J1838−0655: X-Ray Observations with NICER and NuSTAR. We report on the timing and spectral properties of PSR J1838-0655 using joint observations from the Neutron Star Interior Composition Explorer (NICER) and the Nuclear Spectroscopic Telescope Array (NuSTAR). By disentangling the pulsar's emission from its surrounding wind nebula across joint Chandra, NuSTAR, and NICER observations, we find the pulsar's broadband X-ray spectrum (1.3─79 keV) is best-described by a broken power-law model. The model features photon indices of Γ1 = 1.19 ± 0.07 and Γ2 = 1.47 ± 0.02 below and above a break energy of Eb = 7.7 ± 0.8 keV. The resulting unabsorbed 2─10 keV flux from the pulsar is  (9.5−0.3+0.4)×10−12ergcm−2s−1 . Furthermore, timing analysis of NICER data spanning MJD 58250 to 60630 reveals a very large glitch occurring around MJD 59300, characterized by a frequency jump of ∆ν = 29.367(7) × 10−6 Hz, which can be well explained by the vortex creep model. Phase-resolved spectral analysis indicates a clear anticorrelation between the photon index and the pulse intensity, suggesting spectral hardening at the pulse peak.

Keywords: Pulsar timing method, Pulsars