Sazuna/UAT_keywords huggingface dataset:
Multipoint Observations of Magnetic Reconnection in the Martian Magnetotail Triggered by an Interplanetary Magnetic Field Rotation. The induced magnetosphere of Mars is highly dynamic, driven by both the upstream solar wind and the planet's crustal magnetic fields. This variability can occur on timescales much shorter than a single spacecraft orbit, making it difficult to distinguish between spatial and temporal variations in the induced magnetosphere. In this study, we utilize simultaneous multipoint observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) and Tianwen-1 missions to investigate how the induced magnetosphere responds to dynamic changes in the solar wind. We report a magnetic reconnection event observed by MAVEN in the Martian magnetotail, occurring a few minutes after an interplanetary magnetic field (IMF) rotation observed by Tianwen-1 in the upstream solar wind. This reconnection event is characterized by clear Hall magnetic field signatures and high-speed ion jets, indicating the presence of a diffusion region. Our analysis of the change in the magnetic field morphology suggests that this reconnection was likely triggered by this IMF rotation, occurring during the resulting reconfiguration of the induced magnetosphere. This multipoint study demonstrates the important role of dynamic upstream solar wind conditions, particularly IMF rotations, in driving the plasma processes in the Martian magnetotail, contributing to our understanding of solar wind energy and momentum transfer and their roles in ion escape in Mars's hybrid magnetosphere.

Keywords: Space plasmas, Mars, Solar wind, Solar-planetary interactions, Planetary science, Star-planet interactions, Planetary magnetospheres
Mass-dependent Radial Distribution of Single and Binary Stars in the Pleiades and Their Dynamical Implications. The Pleiades is a young open cluster that has not yet dynamically relaxed, making it an ideal target to observe various internal dynamical effects. By employing a well-defined sample of main-sequence (MS) cluster members, including both MS single stars and unresolved MS+MS binaries, we revisited their individual masses and mass functions and quantified the mass dependence of their radial distributions. We found that the mass function of binaries is more top-heavy than that of single stars. Significant mass segregation is observed for both single and binary populations, respectively, with more massive objects concentrated toward the cluster center. Notably, within given mass ranges, binaries are distributed more scattered than single stars, providing direct evidence for more efficient dynamical disruption of binaries in the inner region. The radial distribution of the binary fraction, expressed as the fb–R relation can be characterized by a bimodal shape, with higher fb values in both innermost and outermost regions of the cluster. The lower-mass subsample exhibits a monotonic increase in fb with radius, reflecting the impact of binary disruption. Conversely, for the higher-mass subsample, fb decreases with radius. It can be explained that these massive cluster members, which possess higher binary probabilities, have already undergone significant mass segregation. All these observational evidence and analyses related to the radial mass distribution imply that the Pleiades is currently undergoing a complicated interplay of various internal dynamical effects, of which the modulation between mass segregation and binary disruption is particularly pronounced.

Keywords: Binary stars, Stellar masses, Main sequence stars, Open star clusters, Dynamical evolution
Inhomogeneous Dust Biases Photometric Redshifts and Stellar Masses for LSST. Spectral energy distribution (SED) modeling is one of the main methods to estimate galaxy properties, such as photometric redshifts, z, and stellar masses, M*, for extragalactic imaging surveys. SEDs are currently modeled as light from a composite stellar population attenuated by a geometrically homogeneous foreground dust screen. This is despite evidence from simulations and observations that find large spatial variations in dust attenuation due to the detailed geometry of stars and gas within galaxies. In this work, we examine the impact of this simplistic dust assumption on inferred z and M* for Rubin LSST. We first construct synthetic LSST-like observations (ugrizy magnitudes) from the Numerical Investigation of Hundred Astrophysical Objects (NIHAO)-SKIRT catalog, which provides SEDs from high-resolution hydrodynamic simulations using 3D Monte Carlo radiative transfer. We then infer z and M* from the synthetic observations using the PROVABGS Bayesian SED modeling framework. Overall, the homogeneous dust screen assumption biases both z and M* in galaxies, consistently and significantly for galaxies with dust attenuation AV ≳ 0.5, and likely below. The biases depend on the orientation in which the galaxies are observed. At z = 0.4, z is overestimated by ∼0.02 for face-on galaxies and M* is underestimated by ∼0.4 dex for edge-on galaxies. The bias in photo-z is equivalent to the desired redshift precision level of the LSST "gold sample" and will be larger at higher redshifts. Our results underscore the need for SED models with additional flexibility in the dust parameterization to mitigate significant systematic biases in cosmological analyses with LSST.

Keywords: Interstellar dust, Cosmology, Sky surveys, Observational cosmology, Astrophysical dust processes
Density Fluctuation─Mach Number Scaling in Compressible, High Plasma Beta Turbulence: In Situ Space Observations and High-Reynolds Number Simulations. Understanding the nature of compressible fluctuations in a broad range of turbulent plasmas, from the intracluster medium to the solar wind, has been an active field of research in the past decades. Theoretical frameworks for weakly compressible magnetohydrodynamical turbulence in an inhomogeneous background magnetic field predict a linear scaling of the normalized mass density fluctuation (δρ/ρ0), as a function of the turbulent Mach number ( ),  . However, so far, the scaling relation has been tested only using moderate to low plasma beta (β ≲ 1) solar wind observational data, where the compressibility is weak δρ/ρ0 ∼ 0.1. Here, we combine NASA's Magnetospheric Multiscale Mission data in Earth's magnetosheath, where β ∼ 10 is high, and β ∼ 1/8 highly compressible magnetohydrodynamic turbulence simulations at unprecedented resolutions. Both show that   holds across a broad range of δρ/ρ0,  , and β, demonstrating that   is a robust compressible turbulence relation, going beyond the asymptotics of the weakly compressible theory. We discuss the findings in the context of understanding the nature of strongly compressible turbulent fluctuations and the driving parameter in astrophysical and space plasmas.

Keywords: Space plasmas, Magnetohydrodynamics, Plasma physics, Solar wind, Plasma astrophysics
A New Approach to the Low-frequency Stochastic Gravitational-wave Background: Constraints from Quasars and the Astrometric Hellings–Downs Curve. We present new astrometric constraints on the stochastic gravitational-wave background and construct the first astrometric Hellings–Downs curve using quasar proper motions. From quadrupolar vector spherical harmonic fits to the Gaia proper motions of 1,108,858 quasars, we obtain a frequency-integrated upper limit on the gravitational-wave energy density,   (95% confidence limit), for frequencies between 11.2 nHz and 3.1 × 10‑9 nHz (1.33/t0). However, from the astrometric Hellings–Downs curve that describes the correlated proper motions between 2,104,609,881 quasar pairs as a function of their angular separation, we find a stronger constraint: a characteristic strain of hc ≤ 2.7 × 10‑12 for fref = 1 yr‑1 and   at 95% confidence. We probe down to ±0.005 μas2 yr‑2 in correlated power and obtain the lowest astrometric limit to date. This is also the first time that optical wavelength astrometry surpasses limits from radio-frequency interferometry. This astrometric analysis does not yet reach the sensitivity needed to detect the pulsar timing–based red gravitational-wave spectrum extrapolated to the quasar gravitational-wave sensitivity window, assuming that the turnover in the spectrum occurs at ∼1 nHz for massive black hole binaries. The limits presented here may exclude some exotic interpretations of the stochastic gravitational-wave background.

Keywords: Quasars, Gravitational wave astronomy, Astrometry, Proper motions, Gravitational waves, Time domain astronomy, Gaia
The Einstein Probe Transient EP240414a: Linking Fast X-Ray Transients, Gamma-Ray Bursts, and Luminous Fast Blue Optical Transients. Detections of fast X-ray transients (FXTs) have accrued over the last few decades. However, their origin has remained mysterious. Rapid progress is now being made thanks to timely discoveries and localizations with the Einstein Probe mission. Early results indicate that FXTs may frequently, but not always, be associated with gamma-ray bursts (GRBs). Here, we report on the multiwavelength counterpart of FXT EP240414a, which has no reported gamma-ray counterpart. The transient is located 25.7 kpc in projection from a massive galaxy at z = 0.401. We perform comprehensive photometric and spectroscopic follow-up. The optical light curve shows at least three distinct emission episodes with timescales of ~1, 4, and 15 days and peak absolute magnitudes of MR ∼ −20, ─21, and ─19.5, respectively. The optical spectrum at early times is extremely blue, inconsistent with afterglow emission. It may arise from the interaction of both jet and supernova (SN) shock waves with the stellar envelope and a dense circumstellar medium, as has been suggested for some luminous fast blue optical transients (LFBOTs). At late times, the spectrum evolves to a broad-lined Type Ic SN, similar to those seen in collapsar long GRBs. This implies that the progenitor of EP240414a is a massive star creating a jet-forming SN inside a dense envelope, resulting in an X-ray outburst with a luminosity of ~1048 erg s−1 and the complex observed optical/IR light curves. If correct, this argues for a causal link between the progenitors of long GRBs, FXTs, and LFBOTs.

Keywords: Type Ic supernovae, X-ray transient sources, Gamma-ray bursts
Nonlinear and Nonmonotonic Effect of Ocean Tidal Mixing on Exoplanet Climates and Habitability. Tides play an important role in the circulation and mean state of the Earth's oceans through inducing significant mixing. On other planets, tidal forcings could be highly amplified compared to Earth, such as planets orbiting relatively close to low-mass host stars, or planets having massive and/or close moons. The former scenario is especially important as, due to their abundance and their observational advantages, low-mass stars offer the best chance of finding habitable planets through sheer numbers. By varying the magnitude of tidal forcing over several orders of magnitude in a coupled atmosphere–ocean global circulation climate model, we find that key climatic quantities, such as heat transport intensity and both surface and deep ocean temperature, change with tidal strength in a nonlinear and nonmonotonic manner. We find an optimum value of tidal mixing, approximately 100 times that of Earth's oceans, which minimizes climatic thermal gradients across the planet. In particular, we show that such planets are habitable for stellar flux values at which oceans with weaker or stronger tidal mixing freeze globally, suggesting an important role for ocean tidal mixing in planetary habitability.

Keywords: Exoplanets, Atmospheric circulation, Ocean-atmosphere interactions, Planetary atmospheres, M stars, Astrobiology, Planetary climates, Ocean tides, Atmospheric dynamics, Habitable planets, Exoplanet atmospheres
Single-pulse-based Interstellar Scintillation Studies of RRATs. The nature of irregularly spaced pulses of rotating radio transients (RRATs) complicates interstellar scintillation studies. In this Letter, we report the primary scintillation parameters of a sample of RRATs using pairwise correlations of pulse spectra. Moreover, from the measured scintillation velocities, we constrain their transverse velocities. We also find a reduced modulation index, m = 0.13 ± 0.01, for RRAT J1538+2345. Several possible explanations are discussed. Furthermore, the single-pulse-based interstellar scintillation technique is applicable to other pulsar populations, including nulling pulsars and those with short scintillation timescales, and fast radio bursts.

Keywords: Interstellar scintillation, Radio transient sources
Moving Plasma Structures and Possible Driving Mechanisms of Solar Microflares Observed with High-resolution Coronal Imaging. Solar microflares are ubiquitous in the solar corona, yet their driving mechanisms remain a subject of ongoing debate. Using high-resolution coronal observations from the Solar Orbiter's Extreme Ultraviolet Imager (EUI), we identified about a dozen distinct moving plasma structures (hereafter, " tiny ejections") originating from the centers of three homologous microflares out of four successive events. These tiny ejections propagate roughly perpendicular to the flaring loops. They often originate as dot-like structures with a length scale of approximately 103 km. While these initial dot-like shapes are observable in EUI images, they remain undetectable in the images captured by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. As they propagate, these dot-like structures consistently evolve into loop-like formations, possibly due to the heating of the surrounding magnetic field. Rather than being generated by a series of flux rope eruptions, the tiny ejections appear to result from small-angle magnetic reconnections within a bipolar field. Thus, the microflares associated with these ejections may be driven by magnetic reconnection within braided fields, a process similar to the proposed nanoflare mechanism and distinct from the standard large-scale flare model.

Keywords: Solar corona, Solar flares, Solar magnetic reconnection
Quantitative Exploration of the Similarity of Gamma-Ray Pulsar Light Curves. We introduce and apply a methodology based on dynamic time warping to compare the whole set of gamma-ray light curves reported in the Third Fermi-Large Area Telescope Pulsar Catalogue. Our method allows us to quantitatively measure the degree of global similarity between two light curves beyond comparing indicators such as how many peaks there are, what their separation is, and their width and height. Once the morphology of the light curve is showcased via background subtraction, min-max scaler normalization and rotations are considered to take into account that phase 0 is arbitrary, and the level of detail with which light curves of different pulsars appear is revealed. In many cases, their similarity is striking and occurs disregarding any other timing, physical, or spectral property. In particular, some millisecond pulsars and young pulsars share detailed light-curve morphology.

Keywords: Light curves, Astronomy data analysis, Pulsars
Formation of the Dark Matter–Deficient S0 Galaxy NGC 4111 under the Tidal Interactions. We present high-sensitivity and large-scale atomic hydrogen (H I) observations toward lenticular (S0) galaxy NGC 4111 using the Five-hundred-meter Aperture Spherical Radio Telescope. The column-density map shows that NGC 4111 and seven other different types of galaxies share a huge H I gas complex. The data also suggest that NGC 4111 is interacting with seven galaxies. Moreover, we identified a rotating gas disk associated with NGC 4111 from the H I complex. Still, the H I disk rotation direction has deviated from its stellar disk by about 34 2, indicating that the NGC 4111 galaxy is undergoing a transition from a spiral galaxy to an S0 galaxy by the tidal interactions. The obtained dark matter to stellar mass ratio of NGC 4111 is 3.1 ± 0.7, which is lower than the average value of the local Universe, implying that the interactions may strip its dark matter. Our results suggest that in a galaxy group environment, tidal interactions have a significant effect on galaxy features.

Keywords: Galaxy tides, Interacting galaxies
The Discovery of a 41 s Radio Pulsar PSR J0311+1402 with ASKAP. The emerging population of long-period radio transients (LPTs) shows both similarities and differences with normal pulsars. A key difference is that their radio emission is too bright to be powered solely by rotational energy. Various models have been proposed (including both white dwarf or neutron star origins), and their nature remains uncertain. Known LPTs have minutes-to-hours-long spin periods, while normal pulsars have periods ranging from milliseconds to seconds. Here, we report the discovery of PSR J0311+1402, an object with an intermediate spin period of 41 s, bridging the gap between LPTs and normal pulsars. PSR J0311+1402 exhibits low linear (∼25%) and circular polarization (∼5%) and a relatively steep spectral index (∼ ‑2.3), features similar to normal pulsars. However, its observed spin-down properties place it below the pulsar death line, where pair production and thus radio emission are expected to cease. The discovery of PSR J0311+1402 suggests the existence of a previously undetected population within this intermediate period range, presumably missed due to selection biases in traditional pulsar search methods. Finding more such objects is important to fill the current gap in neutron star spin periods, improving our understanding of the relationships among rotation-powered pulsars and LPTs.

Keywords: Radio transient sources, Radio pulsars, Pulsars
Black Hole Pulsars and Monster Shocks as Outcomes of Black Hole─Neutron Star Mergers. The merger of a black hole (BH) and a neutron star (NS) in most cases is expected to leave no material around the remnant BH; therefore, such events are often considered as sources of gravitational waves without electromagnetic counterparts. However, a bright counterpart can emerge if the NS is strongly magnetized, as its external magnetosphere can experience radiative shocks and magnetic reconnection during/after the merger. We use magnetohydrodynamic simulations in the dynamical spacetime of a merging BH─NS binary to investigate its magnetospheric dynamics. We find that compressive waves excited in the magnetosphere develop into monster shocks as they propagate outward. After swallowing the NS, the BH acquires a magnetosphere that quickly evolves into a split-monopole configuration and then undergoes an exponential decay (balding), enabled by magnetic reconnection and also assisted by the ringdown of the remnant BH. This spinning BH drags the split monopole into rotation, forming a transient pulsar-like state. It emits a striped wind if the swallowed magnetic-dipole moment is inclined to the spin axis. We predict two types of transients from this scenario: (1) a fast radio burst emitted by the shocks as they expand to large radii; and (2) an X-ray/γ-ray burst emitted by the e± outflow heated by magnetic dissipation.

Keywords: Neutron stars, Gamma-ray bursts, Black holes, High energy astrophysics, Relativistic binary stars, Plasma astrophysics, Transient sources, Radio bursts, General relativity, X-ray bursts
The Red Supergiant Progenitor of the Type II Supernova 2024abfl. Linkage between core-collapse supernovae and their progenitors is not fully understood and ongoing effort of searching and identifying the progenitors is needed. SN 2024abfl is a recent Type II supernova that exploded in the nearby star-bursting galaxy NGC 2146, which is also the host galaxy of SN 2018zd. From archival Hubble Space Telescope data, we have found a red source (mF814W ∼ 25) near the location (angular distance ≤0 2) of SN 2024abfl before its explosion. With F814W and F606W photometry, we found that the properties of this source matched a typical red supergiant (RSG) moderately reddened by interstellar dust at the distance of the host galaxy. We conclude that the SN 2024abfl had an RSG progenitor with initial mass of 9 –12 M⊙.

Keywords: Type II supernovae, Red supergiant stars, Stellar evolution
Fast Transients from Magnetic Disks around Nonspinning Collapsar Black Holes. Most black holes (BHs) formed in collapsing stars have low spin, though some are expected to acquire a magnetic accretion disk during the collapse. While such BH disks can launch magnetically driven winds, their physics and observational signatures have remained unexplored. We present global 3D general relativistic magnetohydrodynamic simulations of collapsing stars that form slowly spinning BHs with accretion disks. As the disk transitions to a magnetically arrested state, it drives mildly relativistic, wobbling, collimated magnetic outflows through two mechanisms: steady outflows along vertical magnetic field lines ("Blandford–Payne jets") and magnetic flux eruptions. With isotropic-equivalent energy of Eiso ≈ 1052 erg, exceeding that of relativistic jets from BHs with spin a ≲ 0.25, the disk outflows unbind the star, ultimately capping the final BH mass at MBH ≈ 4 M⊙. Once the outflows emerge from the star, they produce mildly relativistic shock breakout and cooling emission. Our cooling emission estimates suggest a bright near-ultraviolet and optical signal at absolute magnitude MAB ≈ ‑16 lasting for several days. This indicates that disk winds could be responsible for the first peak in the double-peaked light curves observed in Type Ib/c supernovae (SNe) or power another class of transients. The detection rate in the upcoming Rubin Observatory and ULTRASAT/UVEX will enable us to differentiate between competing models for the origin of the first SN peak and provide constraints on the physics and formation rate of accretion disks in core-collapse SNe.

Keywords: Hydrodynamical simulations, Gamma-ray bursts, Core-collapse supernovae, Transient sources, Stellar mass black holes, Nonrotating black holes, Stellar accretion disks, Ultraviolet transient sources, Astrophysical black holes
A Rotational Disruption Crisis for Zodiacal Dust. A systematic torque from anisotropic radiation can rapidly spin up irregular grains to the point of breakup. We apply the standard theory of rotational disruption from radiative torques to solar system grains, finding that grains with radii ∼0.03─3 μm at 1 au from the Sun are spun to the point of breakup on timescales ≲1 yr even when assuming them to have an unrealistically high tensile strength of pure meteoritic iron. Such a rapid disruption timescale is incompatible with both the abundance of micron-sized grains detected in the inner solar system and with the low production rate of β-meteoroids. We suggest the possibility that zodiacal grains have a strong propensity to attain rotational equilibrium at low angular velocity (a so-called low-J attractor) and that the efficacy of rotational disruption in the solar system—and likely elsewhere—has been greatly overestimated.

Keywords: Zodiacal cloud, Dust physics, Interplanetary dust, Dust destruction