Sazuna/UAT_keywords huggingface dataset:
A Cold and Superpuffy Planet on a Prograde Orbit. We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density &lt;0.2 g cm−3 on a 105 days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M⊕ at 95% confidence. The radial velocities also exhibit the Rossiter─McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity  λ=−15−44+50 ° (∣λ∣ &lt; 80° at 3σ). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest "superpuff" planets yet discovered.

Keywords: Radial velocity, Transit photometry, Cold Neptunes, Exoplanets
Seafloor Weathering and Stochastic Outgassing Unlikely to Significantly Shorten the Future Lifespan of Earth's Terrestrial Biosphere. Current understanding suggests that as the Sun brightens in the far future, Earth's carbonate-silicate cycle will offset increasing temperatures by drawing CO2 out of the atmosphere, ultimately leading to the extinction of all terrestrial plant life via either overheating or CO2 starvation. Most previous estimates put the future lifespan of Earth's terrestrial biosphere at ∼1 billion yr, but recent work used a new coupled climate-continental weathering model with up-to-date parameter constraints to revise this estimate upward to 1.6─1.86 billion yr. In this study, we extend the model to examine the impacts of seafloor weathering and stochastic variations in CO2 outgassing rates on the remaining lifespan of Earth's terrestrial biosphere. We find that if seafloor weathering has a stronger feedback than continental weathering and accounts for a large portion of global silicate weathering, then the remaining lifespan of the terrestrial biosphere can be shortened, but a lifespan of more than 1 billion yr (Gyr) remains likely. Similarly, stochastic fluctuations in outgassing rates can have a significant impact if the size of the fluctuations exceed those observed over the last 1 billion yr. The impact of weak seafloor weathering and lower variability stochasticity are minor. Our work provisionally supports a lengthened lifespan of Earth's terrestrial biosphere, suggests robustness of this lengthened lifespan to planetary parameters that may vary among exoplanets, and identifies seafloor weathering as a key process that requires further study and constraint.

Keywords: Geological processes, Atmospheric evolution, Astrobiology, Habitable planets
XRISM Observations of the Prototypical Cold Front in A3667. We present high-resolution X-ray spectroscopy of the merging galaxy cluster A3667 with XRISM/Resolve. Two observations, targeting the cluster X-ray core and the prototypical cold front, were performed with exposures of 105 and 276 ks, respectively. We find that the gas in the core is blueshifted by vz ∼ −200 km s−1 relative to the brightest cluster galaxy, while the low-entropy gas inside the cold front is redshifted by vz ∼ 200 km s−1. As one moves further off-center across the front, the line-of-sight (LoS) velocity changes significantly, by  ∆vz=535−154+167  km s−1, back to the value similar to that in the core. There are no significant LoS velocity gradients perpendicular to the cluster symmetry axis. These features suggest that the gas forming the cold front is flowing in the plane oriented along the LoS, supporting an offset merger scenario in which the main cluster has passed in front of the subcluster and induced rotation of the core gas in the plane perpendicular to the sky. The region just inside the front exhibits the largest LoS velocity dispersion seen across two pointings, σz ∼ 420 km s−1, which can be interpreted as a developing turbulence or a projection of the LoS velocity shear within the front. The large LoS velocity jump across the cold front, combined with the lack of Kelvin─Helmholtz instability on the surface of the front, suggests some mechanism to suppress it. For example, a magnetic field with B &gt; 5 μG is required if the cold front is stabilized by magnetic draping.

Keywords: Galaxy clusters, High resolution spectroscopy, Intracluster medium
A Milliarcsecond Localization Associates FRB 20190417A with a Compact Persistent Radio Source and an Extreme Magnetoionic Environment. We report the milliarcsecond localization of a high (∼1379 pc cm−3) dispersion measure (DM) repeating fast radio burst (FRB), FRB 20190417A. Combining European VLBI Network detections of five repeat bursts, we confirm the FRB's host to be a low-metallicity, star-forming dwarf galaxy at z = 0.12817, similar to the hosts of FRB 20121102A, FRB 20190520B, and FRB 20240114A. We also confirm that it is associated with a previously reported persistent radio source (PRS), which is compact on milliarcsecond scales. Visibility-domain model fitting constrains the transverse physical size of the PRS to &lt;23 pc and yields an integrated flux density of 190 ± 40 μJy at 1.4 GHz. Though we do not find significant evidence for DM evolution, FRB 20190417A exhibits a time-variable rotation measure (RM) ranging between +3958 ± 11 rad m−2 and +5061 ± 24 rad m−2 over a 50-day period. We find no evidence for intervening galaxy clusters in the FRB's line of sight and place a conservative lower limit on the rest-frame host DM contribution of 1228 pc cm−3 (90% confidence)—the largest known for any FRB so far. This system strengthens the emerging picture of a rare subclass of repeating FRBs with large and variable RMs, above-average host DMs, and luminous PRS counterparts in metal-poor dwarf galaxies. Our results suggest that these systems are the result of environmental selection, or a distinct engine for FRB emission.

Keywords: High energy astrophysics, Very long baseline interferometry, Transient sources, Burst astrophysics, Radio bursts, Radio transient sources
Water Vapor Emission at the Warm Cavity Wall of the HD 100546 Disk as Revealed by ALMA. We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of the water line at 183 GHz in the disk around the Herbig star HD 100546. The water vapor emission peaks at the inner edge of the warm dust cavity, located ∼15 au from the central star. We attribute this to thermal desorption at the water snow line, shifted outward at the dust cavity wall directly heated by the intense radiation. This represents the first spatially resolved image of the water snow line using ALMA observations of the main water isotopologue in a protoplanetary disk. The water emission morphology peaking inside the first dust ring is consistent with previous ALMA detections of oxygen-bearing complex organic molecules in the disk, including thermally desorbed methanol. These findings signal that warm cavities of transition disks provide ideal targets to directly reconstruct the spatial distribution of water vapor and the snow line location with ALMA and directly connect water vapor emission to ice desorption of complex organic species.

Keywords: Radio interferometry, Water vapor, Protoplanetary disks, Planet formation
Dipole Polarizability of Finite Nuclei as a Probe of Neutron Stars. Nuclear ground state and collective excitation properties provide a means to probe the nuclear matter equation of state and establish connections between observables in finite nuclei and neutron stars. Specifically, the electric dipole polarizability, measured with high precision in various neutron-rich nuclei, serves as a robust constraint on the density dependence of the symmetry energy. In this Letter, we employ a class of relativistic energy density functionals in a twofold process: first, to link the electric dipole polarizability from recent experiments to the slope of the symmetry energy, and second, to translate this information into constraints on the tidal deformability and radii of neutron stars, in connection with multimessenger astrophysical observations from pulsars and binary neutron stars. We provide compelling evidence that the electric dipole polarizability represents a key nuclear observable to probe the neutron star properties. By significantly reducing the uncertainties in the mass─radius plane, our findings also align with recent multimessenger observations.

Keywords: Neutron stars, Relativistic binary stars, Nuclear astrophysics, Gravitational waves, Nuclear physics
Formation of the Little Red Dots from the Core Collapse of Self-interacting Dark Matter Halos. We present a statistical study of black hole (BH) formation and growth seeded by gravothermal core collapse of self-interacting dark matter (SIDM) halos at high redshift, using a cosmological semianalytical framework based on Monte Carlo merger trees. We demonstrate that gravothermal collapse naturally leads to BH formation in high-concentration halos at a characteristic mass scale set by the SIDM cross section and occurs predominantly in the early Universe. This mechanism is particularly promising for explaining the abundance of the little red dots (LRDs)—early active galactic nuclei whose BHs appear dramatically overmassive relative to their host galaxies. By incorporating this seeding process with simple models of BH growth and assuming a 100% duty cycle, we broadly reproduce the observed LRD mass function for velocity-dependent cross sections of σ0m ∼ 30 cm2 g−1 and ω ∼ 80 km s−1, which are consistent with independent constraints from local galaxies. While higher values of σ0m (or ω) would overpredict the low-mass (or high-mass) end of the BH mass function, such deviations could be reconciled by invoking a reduced duty cycle or lower Eddington ratio. Our results suggest that the demographics of high-redshift BHs can serve as a novel and complementary probe of SIDM physics.

Keywords: Supermassive black holes, Galaxy dark matter halos, Dark matter, Early universe
Origin of Pulsed Radio Emission from Magnetars. Extended periods of radio pulsations have been observed for six magnetars, displaying characteristics different from those of ordinary pulsars. In this Letter, we argue that radio emission is generated in a closed, twisted magnetic flux bundle originating near the magnetic pole and extending beyond 100 km from the magnetar. The electron─positron flow in the twisted bundle has to carry electric current and, at the same time, experiences a strong drag from the radiation field of the magnetar. This combination forces the plasma into a "radiatively locked" state with a sustained two-stream instability, generating radio emission. We demonstrate this mechanism using novel first-principles simulations that follow the plasma behavior by solving the relativistic Vlasov equation with the discontinuous Galerkin method. First, using one-dimensional simulations, we demonstrate how radiative drag induces the two-stream instability, sustaining turbulent electric fields. When extended to two dimensions, the system produces electromagnetic waves, including superluminal modes capable of escaping the magnetosphere. We measure their frequency and emitted power and incorporate the local simulation results into a global magnetospheric model. The model explains key features of the observed radio emission from magnetars: its appearance after an X-ray outburst, wide pulse profiles, luminosities ∼1030 erg s−1, and a broad range of frequencies extending up to ∼100 GHz.

Keywords: Magnetospheric radio emissions, High energy astrophysics, Plasma astrophysics, Magnetars, Astronomical simulations
Converged Simulations of the Nozzle Shock in Tidal Disruption Events. A star experiences a tidal disruption event (TDE) after passing too close to a massive black hole. When the debris returns to pericenter on the second passage, it is compressed, leading to the formation of nozzle shocks (in the orbital plane) and pancake shocks (perpendicular to the orbital plane). Resolving these shocks is a long-standing problem in the hydrodynamic simulations of parabolic TDEs. Excessive numerical energy dissipation or heating unrealistically expands the stream. In this Letter, we apply adaptive particle refinement to our 3D general relativistic smoothed particle simulations to locally increase the resolution near the pericenter. We achieve resolutions equivalent to 6.55 × 1011 particles, allowing us to converge on the true energy dissipation. We conclude that only 4 × 10−5 of the orbital energy is dissipated in nozzle shocks for a Sunlike star tidally disrupted by a 106 solar-mass black hole, and therefore the nozzle shocks are unlikely to be important in the evolution of TDEs.

Keywords: Hydrodynamical simulations, Tidal disruption, Supermassive black holes, Astronomical simulations
Helical Magnetic Field in the Acceleration─Collimation Zone of the M87 Jet. Relativistic jets from supermassive black holes are expected to be magnetically launched and guided, with magnetic energy systematically converted to bulk kinetic energy throughout an extended acceleration─collimation zone (ACZ). A key prediction of magnetohydrodynamic (MHD) models is a transition from poloidally dominated fields near the engine to toroidally dominated fields downstream, yet direct tests within the ACZ are hampered by weak polarization and strong Faraday rotation. We report quasi-simultaneous, high-sensitivity, multifrequency very long baseline interferometric polarimetry of M87 spanning 1.4─24.4 GHz. We present high-fidelity, Faraday-rotation-corrected maps of intrinsic linear polarization that continuously resolve the ACZ in the deprojected distance range of ∼9.0 × 103 to ∼3.6 × 105 gravitational radii from the black hole. The maps reveal pronounced north─south asymmetries in fractional linear polarization and electric vector position angle (EVPA), peaking in the inner ACZ at a projected distance of ∼20 mas along the jet and remaining prominent out to ∼100 mas. These signatures are best reproduced by models with a large-scale ordered helical field that retains a substantial poloidal component—contrary to the rapid toroidal dominance expected under steady ideal MHD. This tension implies ongoing magnetic dissipation that limits toroidal buildup over the ACZ. The handedness of the helix provides an independent constraint on the BH's spin direction, supporting a spin vector oriented away from the observer, consistent with the orientation inferred from horizon-scale imaging. Farther downstream, the asymmetries diminish, and the EVPA and fractional polarization distributions become more symmetric; we tentatively interpret this as evolution toward a more poloidally dominated configuration, while noting current sensitivity and dynamic range limits.

Keywords: Black hole physics, Magnetohydrodynamics, Very long baseline interferometry, Relativistic jets, Magnetic fields, Active galactic nuclei, Polarimetry
Helium Atmospheres May Hide in Current Exoplanet Analysis Frameworks. The increasing number of detailed exoplanet observations offers an opportunity to refine our analyses and interpretations. Here, we show that atmospheres that appear volatile-rich and/or cloudy may instead be helium-rich. As transmission spectra constrain the atmospheric scale height (H), a He-enriched atmosphere can be misinterpreted as H2-dominated water-rich to bring the mean molecular weight (μ) to intermediate values (∼4−10) when He/H2 is fixed. Similarly, a cloud deck can reduce the spectral features, and thus the apparent (i.e., cloud-free equivalent) H. We present a proof-of-concept reanalysis of HD 209458 b's JWST transmission spectrum treating He/H2 as a free parameter, resulting in sets of He-rich solutions. We argue that He enhancement must be considered to reliably constrain atmospheric composition, be sensitive to a more diverse planetary population, and ultimately yield robust trends to inform formation and evolution pathways. Looking ahead, we suggest leveraging insights from differences in pressure-broadening effects, outflow measurements, and atmospheric chemistry to disentangle reliably between He-, volatile-rich, and cloudy atmospheres—while recognizing that associated models need targeted upgrades to reach the fidelity level required to this end.

Keywords: Exoplanet atmospheric composition , James Webb Space Telescope, Exoplanet atmospheres, Transmission spectroscopy
AT2025ulz and S250818k: Zooming in with the Hubble Space Telescope. AT2025ulz is an optical/near-infrared transient discovered during follow-up of the candidate gravitational wave (GW) event S250818k. Its young age (≲1 day), rapid decline, and strong color evolution over the first 48 hr classify it as a potential kilonova candidate. In this work, we present the results of our observing campaign, carried out with the Gran Telescopio Canarias and the Hubble Space Telescope (HST). Although the early time evolution of AT2025ulz resembles some aspects of a kilonova, its rapid onset (∼3 hr after the GW trigger) and luminosity (a factor of ∼5 brighter than AT2017gfo in g band) are difficult to reproduce. Only a small subset of our kilonova models matches its multicolor light curve, and the inferred ejecta mass is uncomfortably large given the low chirp mass (≲0.87 M⊙) of the GW candidate. HST observations place the transient within a nearby (z = 0.08489) spiral galaxy with ongoing star formation and measure a color (F336W − F160W ≍ 1.4 mag) that is too blue to match with a kilonova. Our data support the classification of AT2025ulz as a supernova, initially undergoing a shock-cooling phase and later entering its photospheric phase and spectroscopically identified via its broad absorption features.

Keywords: Neutron stars, Gamma-ray bursts, Gravitational waves, Time domain astronomy, Compact objects, Supernovae
Beta-dependent Properties of Solar Wind Current Sheets at 1 au. We utilize plasma turbulence in interplanetary coronal mass ejections as a natural laboratory to analyze more than 4600 current sheets observed over a broad range of electron and proton beta values, 10−2 ≲ βe ≲ 10 and 10−3 ≲ βp ≲ 10. The analysis shows that the shear angle ∆θ and the thickness λCS of the current sheets depend on both electron and proton beta. Specifically, the dependencies on electron beta are  ∆θ≍12.6°βe0.41  and  λCS/λp≍1.9βe0.26 , where λp is the local proton inertial length. We argue that the beta dependence of the shear angle is an intrinsic feature of solar wind turbulence arising from the natural correlation between turbulence intensity and plasma beta. In contrast, the beta dependence of current sheet scales is likely a general characteristic of plasma turbulence. According to recent theory, current sheets formed in turbulence are disrupted by the electron tearing instability once their thickness is smaller than a critical scale. We demonstrate that normalizing the thickness of current sheets by this critical scale eliminates the dependence on beta across the entire range of plasma beta. This observation not only supports the theory suggesting that current sheets mediate the transition from the inertial to the kinetic cascade through the electron tearing instability, but also demonstrates the plausibility of similar processes in astrophysical plasma. The presented results also indicate that the theory may be applicable beyond its formal limits, me/mi ≪ β ≪ 1.

Keywords: Space plasmas, Solar magnetic reconnection, Interplanetary turbulence, Solar wind, Solar coronal mass ejections
Atmospheric Collapse and Reinflation through Impacts for Terrestrial Planets around M Dwarfs. Detection of an atmosphere around a terrestrial exoplanet will be a major milestone in the field, but our observational capacities are biased towards tidally locked, close-in planets orbiting M dwarf stars. The atmospheres of these planets are vulnerable to atmospheric erosion and collapse due to condensation of volatiles on the nightside. However, these condensed volatiles constitute a stable reservoir that could be revaporized by meteorite impacts and reestablish the atmospheres. Through a simple energy balance model applied to atmospheric evolution simulations with stochastic impacts, we assess the viability and importance of this mechanism for CO2 atmospheres. We find that moderate-sized impactors (5─10 km diameter) occurring at a frequency of 1─100 Gyr−1 can regenerate observable transient atmospheres on previously airless planets. We focus on specific targets from the James Webb Space Telescope Director's Discretionary Time Rocky Worlds programme and compute the fraction of their evolution spent with a transient CO2 atmosphere generated through this mechanism. We find this fraction can reach 70% for GJ 3929 b, 50% for LTT 1445 Ac, and 80% for LTT 1445 Ab at high impact rates and strong CO2 outgassing over the planet's lifetime. We also show that atmospheric collapse can shield volatiles from escape, particularly in the early, high X-ray and ultraviolet phase of M dwarf evolution. Overall, our work suggests that terrestrial planet atmospheres may not evolve monotonically but instead may be shaped by episodic external forcings.

Keywords: Extrasolar rocky planets, M dwarf stars, Exoplanet atmospheric dynamics, Exoplanet atmospheres, Exoplanet atmospheric evolution
The Magnetic Fields of the Dusty Nuclei and Molecular Outflows of Arp 220. Galaxy mergers trigger starburst activity and galactic outflows that enrich the circumgalactic medium (CGM), profoundly impacting galaxy evolution. These phenomena are intrinsically linked to the physical conditions of the medium, which is permeated by magnetic (B) fields affecting its transport and dynamics. Here, we spatially resolve,  0.″24  (96 pc), the B-fields in the dusty and molecular outflows of Arp 220, the closest (78 Mpc) ultraluminous infrared galaxy hosting two interacting nuclei, denoted as East and West. We perform Atacama Large Millimeter/submillimeter Array 870 μm dust continuum polarization and CO(3─2) emission line polarization and report the first detection of CO(3─2) emission line polarization through the Goldreich─Kylafis effect in an outflow. Dust polarization shows that Arp 220 E has a spiral-like B-field on the disk with a linear polarization fraction of 0.4% ± 0.1% that may produce the detected circular polarization passing through foreground-aligned dust grains. Arp 220 W reveals a B-field parallel to the red- and blueshifted outflows in both the dust and emission line polarization maps. The outflows show a dust polarization of 0.2%, while the CO(3─2) emission line polarization is 1%─2% at 4σ─6σ significance across independent velocity channels. A highly polarized (3%─5%) dusty bridge has a B-field orientation of ∼110° connecting both nuclei. Mean B-field strengths of 1.1 and 9.5 mG for the blue- and redshifted outflows, respectively, are estimated. These strong B-fields are attributed to amplification by compression in nuclear clouds and supernova remnants. This amplified B-field is likely sustained by the turbulent kinetic energy in the outflow and may be critical in directing the transport of metals and cosmic rays into the CGM.

Keywords: Molecular gas, Galactic winds, Spectropolarimetry, Polarimetry, Galaxy mergers, Ultraluminous infrared galaxies, Extragalactic magnetic fields