Sazuna/UAT_keywords huggingface dataset:
Ringed versus Ringless Worlds: How Poynting─Robertson Drag Shapes Rings across the Solar System. Planetary rings are not only ubiquitous around the giant planets in the outer solar system, but have also been discovered around several small distant bodies. In contrast, no rings have been observed around any inner solar system objects. To constrain the dynamical origin of this ringed-versus-ringless dichotomy, we employ a numerically cross-checked analytical model of gigayear-scale Poynting─Robertson (PR) drag due to the solar flux acting on an isolated particle, expressed as a function of the host body's heliocentric distance apla and the particle radius rpar. Here we show that, in the absence of additional perturbations, PR drag alone can explain the observed ring architecture of the solar system: outer planets and Centaurs/trans-Neptunian objects are able to retain rings for the age of the solar system, whereas any rings around the inner planets are removed on much shorter timescales. Because the PR-drag lifetime scales steeply with heliocentric distance  (τdecay∝apla2rpar) , we predict that forthcoming surveys will reveal an ever-growing population of ring-bearing bodies in the distant solar system.

Keywords: Planetary system formation, Planetary dynamics, Planetary rings, Solar system evolution
Ultraviolet Spectral Evidence for Ansky as a Slowly Evolving Featureless Tidal Disruption Event with Quasiperiodic Eruptions. X-ray quasiperiodic eruptions (QPEs) are rare and enigmatic phenomena that increasingly show a connection to tidal disruption events (TDEs). However, the recently discovered QPEs in ZTF19acnskyy ("Ansky") appear to be linked to an active galactic nucleus (AGN) rather than a TDE, as their slow decay and AGN-like variability differ markedly from that of typical TDEs. This finding may imply broader formation channels for QPEs. To further investigate Ansky's nature, we obtained a timely ultraviolet (UV) spectrum, which reveals a featureless, TDE-like spectrum devoid of broad optical or UV emission lines. Additionally, the steep UV continuum, fitted by a power law with an index of −2.6, aligns more closely with TDEs than with AGNs. Compared to other featureless TDEs, Ansky exhibits a significantly lower blackbody luminosity (∼1043 erg s−1) and much longer rise/decay timescales, suggesting a distinct TDE subclass. An offset TDE involving an intermediate-mass black hole is unlikely, given its position consistent with the galactic center, with a 3σ upper limit of 54 pc. Instead, we propose that Ansky may result from the tidal disruption of a post-main-sequence star by a typical supermassive black hole. Our findings strengthen the growing evidence for TDE─QPE associations, although other formation channels for QPEs remain plausible and await future observational efforts.

Keywords: Supermassive black holes, Tidal disruption, Time domain astronomy, High energy astrophysics
Comprehensive X-Ray Observations of the Exceptional Ultralong X-Ray and Gamma-Ray Transient GRB 250702B with Swift, NuSTAR, and Chandra: Insights from the X-Ray Afterglow Properties. GRB 250702B is an exceptional transient that produced multiple episodes of luminous gamma-ray radiation lasting for &gt;25 ks, placing it among the class of ultralong gamma-ray bursts (GRBs). However, unlike any known GRB, the Einstein Probe detected soft-X-ray emission up to 24 hr before the gamma-ray triggers. We present comprehensive X-ray observations of the transient's "afterglow" obtained with the Neil Gehrels Swift Observatory, the Nuclear Spectroscopic Telescope Array, and the Chandra X-ray Observatory between 0.5 and 65 days (observer frame) after the initial high-energy trigger. The X-ray emission decays steeply as ∼t−1.9 and shows short-timescale X-ray variability (∆T/T &lt; 0.03) in both Swift and NuSTAR, consistent with flares superposed on an external shock continuum. Serendipitous detections by the Swift Burst Alert Telescope out to ∼0.3 days and continued NuSTAR variability to ∼2 days imply sustained central engine activity; including the early Einstein Probe X-ray detections, the required engine duration is ≳3 days. Afterglow modeling favors the combination of forward- and reverse-shock emission in a windlike (k ≍ 2) environment. These properties, especially the long-lived engine and early soft-X-ray emission, are difficult to reconcile with a collapsar origin, and GRB 250702B does not fit neatly with canonical ultralong GRBs or relativistic tidal disruption events (TDEs). A "hybrid" scenario, in which a star is disrupted by a stellar-mass black hole (a micro-TDE), provides a plausible explanation, although a relativistic TDE from an intermediate-mass black hole remains viable.

Keywords: X-ray astronomy, Gamma-ray bursts, Black holes, High energy astrophysics, Relativistic jets, X-ray transient sources, Time domain astronomy, Gamma-ray transient sources
Ion-scale Solitary Structures in the Solar Wind Observed by Solar Orbiter and Parker Solar Probe. We investigate a class of ion-scale magnetic solitary structures in the solar wind, characterized by distinct magnetic field enhancements and bipolar rotations over spatial scales of several proton inertial lengths. These structures are revisited using high-resolution data from the Solar Orbiter and Parker Solar Probe missions. Using a machine learning─based method, we identified nearly a thousand such structures, providing new insights into their evolution and physical properties. Statistical analysis shows that these structures are more abundant closer to the Sun, with occurrence rates peaking around 30−40 R⊙ and decreasing farther out. High-cadence measurements reveal that these structures are predominantly found in low-beta (β ≤ 1) environments, with consistent fluctuations in density, velocity, and magnetic field. Magnetic field enhancements are often accompanied by plasma density drops, which, under near-pressure balance, limit field increases. This leads to small fractional field enhancements near the Sun (approximately 0.01 at 20 R⊙), making detection challenging. Magnetic field variance analysis indicates that these structures are primarily oblique to the local magnetic field. Alfvénic velocity─magnetic field correlations suggest that most of these structures, unlike most near-Sun solar wind fluctuations, exhibit sunward-directed Alfvénic polarization in the plasma frame. We compare these findings with previous studies, discussing possible generation mechanisms and their implications for the turbulent cascade in the near-Sun Alfvénic solar wind. While these structures might be Alfvénic solitons, vortices, or flux ropes, we refrain from a definitive classification pending further evidence. Further high-resolution observations and simulations are needed to fully understand their origins and impacts.

Keywords: Solar wind, Alfven waves, Classification
Magnetars in Binaries as the Engine of Actively Repeating Fast Radio Bursts. The association between FRB 20200428D and the Galactic magnetar SGR J1935+2154 makes magnetars the leading engine of cosmological fast radio bursts (FRBs). However, there is a list of puzzles for this magnetar-for-all-FRBs scenario: known Galactic magnetars are all isolated, and none of them are active repeaters; some cosmological repeaters have extremely high repetition rates but without any measurable spin-related periodicity; some show long-term periodic active windows; and some show diverse rotation measure (RM) evolution patterns, such as quasiperiodic fluctuations, sign reversals, and abrupt RM flares. Here we propose a unified theoretical paradigm for FRBs within the framework of the magnetar engine: most active repeating FRBs originate from magnetars in binary systems with nearly aligned rotation and magnetic axes, some of which have a triple-aligned geometry, i.e., an alignment with the orbital axis as well, whereas apparent nonrepeaters and inactive repeaters originate from magnetars in isolated systems or in binaries with a misaligned geometry. By studying various magnetar formation channels using population synthesis, we show that a few percent of magnetars in the Universe can be in binary systems, most with a massive star companion and some with aligned geometry. We suggest that such binary systems can account for the rich phenomenology of active repeaters. We suggest that the existence of a companion helps to maintain the aligned geometry and that the companion may play an active role in triggering FRBs in an active repeater source.

Keywords: Magnetars, Binary stars, Radio transient sources
Strontium-84 Enrichments in Presolar Grains Provide First Evidence of p-process Nucleosynthesis in Core-collapse Supernovae. This study reports detection of rare p-process isotopes within presolar grains. Presolar grains are relic dust grains from dying stars. These microscopic dust particles are found in primitive solar system materials. Their distinct isotopic compositions record the nucleosynthetic processes in their parent stars and the Galactic chemical environment in which these stars formed. We studied presolar graphite grains of high-density type from the Murchison meteorite and found five grains with subgrains that show enrichments in 84Sr compared to the solar abundance. 84Sr is the neutron-deficient isotope of strontium that can be produced in the deep oxygen-rich interior of high-mass stars that end their lives as core-collapse supernovae. The observed 84Sr excesses cannot be produced in low-mass asymptotic giant branch stars, the source of most high-density presolar graphites found in meteorites. High-density graphites with embedded 84Sr excesses are, instead, compatible with a core-collapse supernovae origin. The graphite subgrains condensed from carbon-rich materials in the outer layers of core-collapse supernovae, where 84Sr was destroyed by neutron captures during hydrostatic evolution of the stars and their final explosion. Based on current theoretical stellar models, a few percent of contribution from the inner regions of core-collapse supernovae, which are enriched in p-process nuclides, to the outer carbon-rich regions is the most likely explanation for the observed enrichment of 84Sr in the subgrains of the high-density graphites. In this study, we present the first observational evidence that core-collapse supernovae produce and eject isotopes made by the p-process.

Keywords: Pre-solar nebulae, Core-collapse supernovae, P-process, Circumstellar grains, Stellar nucleosynthesis, Circumstellar dust
The Hubble Tension Resolved by the DESI Baryon Acoustic Oscillations Measurements. The Lambda cold dark matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological observations. However, severe challenges to the phenomenological ΛCDM model have emerged recently, including the Hubble constant tension and the significant deviation from the ΛCDM model reported by the Dark Energy Spectroscopic Instrument (DESI) collaboration. Despite many explanations for the two challenges having been proposed, their origins are still intriguing mysteries. Here, we investigate the DESI baryon acoustic oscillation (BAO) measurements to interpret the Hubble constant tension. Employing a nonparametric method, we find that the dark energy equation of state w(z) evolves with redshift from DESI BAO data and Type Ia supernovae. From the Friedmann equations, the Hubble constant (H0) is derived from w(z) model-independently. We find that the values of H0 show a descending trend as a function of redshift, and can effectively resolve the Hubble constant tension. Our study finds that the two unexpected challenges to the ΛCDM model can be understood in one physical framework, e.g., dynamical dark energy.

Keywords: Hubble constant, Type Ia supernovae, Baryon acoustic oscillations, Dark energy
Early Evidence for Polar Orbits of Sub-Saturns around Hot Stars. Sub-Saturns have been reported to preferentially occupy near-polar orbits, but this conclusion has so far been based primarily on systems with cool host stars; obliquity measurements for sub-Saturns orbiting hot stars remain scarce. Expanding the census into the hot-star regime is essential to test whether the polar preference persists across the Kraft break and to diagnose the underlying excitation mechanisms. In this work, we present Rossiter─McLaughlin observations of TOI-1135b, a sub-Saturn orbiting a hot star with Teff = 6320 ± 120 K, using WIYN/NEID. We confirm its near-polar architecture, measuring a sky-projected obliquity of λ =  −68.°1−5.3+7.5 , and a true obliquity of ψ =  72.°2−6.6+6.4 . Coupling our new measurement with stellar-obliquity data from the literature, we find that sub-Saturns and hot Jupiters around cool stars are unlikely to be drawn from the same parent distribution at the 5.2σ level, consistent with weaker tidal realignment for lower-mass planets. Of the two known misaligned sub-Saturns around hot stars, both are near-polar, suggesting that the polar preference may extend above the Kraft break. Moreover, their obliquities lie near ∼65°, supporting predictions from secular resonance crossing for sub-Saturns around rapidly rotating hot stars.

Keywords: Exoplanet dynamics, Planetary theory, Exoplanets, Planetary alignment, Exoplanet systems, Exoplanet astronomy, Star-planet interactions
Identification and Photometric Classification of Extragalactic Transients in the Vera C. Rubin Observatory's Data Preview 1. The Vera C. Rubin Observatory will soon survey the southern sky, delivering a depth and sky coverage that is unprecedented in time-domain astronomy. As part of commissioning, Data Preview 1 (DP1) has been released. It comprises a Legacy Survey of Space and Time (LSST) Commissioning Camera observing campaign between 2024 November and December with multiband imaging of seven fields, covering roughly 0.4 deg2 each, providing a first glimpse into the data products that will become available once the LSST begins. In this work, we search three fields for extragalactic transients. We identify eight new likely supernovae (SNe), and three known ones from a sample of 369,644 difference image analysis objects. Photometric classification using Superphot+ assigns subclasses with &gt;95% confidence to only one SN Ia and one SN II in this sample. Our findings are in agreement with SN detection rate predictions of 15 ± 4 SNe from simulations using simsurvey. The SN detection rate in the data is possibly affected by the lack of suitable templates. Nevertheless, this work demonstrates the quality of the data products delivered in DP1 and indicates that the Rubin Observatory's LSST is well placed to fulfill its discovery potential in time-domain astronomy.

Keywords: Surveys, Time domain astronomy, Transient detection, Supernovae
Turbulence-driven Anisotropic Acceleration of Energetic Electrons in Solar Wind Current Sheets. Coherent structures in the solar wind, such as current sheets, are widely recognized as potential sites for energy dissipation and particle acceleration. However, the mechanisms driving energetic electron acceleration within these structures, particularly the role of embedded turbulence, remain observationally unconstrained. In this Letter, we present a statistical analysis of 103 mesoscale current sheet events observed by the WIND spacecraft. Our results reveal modest enhancements in energetic electron fluxes (40─310 keV) within these structures. More notably, the acceleration exhibits a pronounced anisotropy, with a preferential energization in the perpendicular direction. Further analyses indicate that this anisotropic energization is strongly modulated by the local turbulence. The perpendicular energy spectrum systematically hardens with increasing intermittency and with higher values of the local energy transfer rate. These findings are consistent with a turbulence-driven, second-order Fermi-like process, where acceleration efficiency is enhanced when the interaction scale permits quasi-adiabatic scattering. The observed perpendicular energization appears closely linked to the compressive, intermittent structures frequently generated within the current sheets. The subtle nature of the observed signatures also provides an explanation for the historical scarcity of definitive evidence for energetic electron acceleration in solar wind current sheets. By establishing the first systematic observational connection between anisotropic acceleration signatures and scale-dependent turbulence diagnostics, this study might provide a critical step toward bridging theoretical models and in situ observations of energetic electron acceleration in the heliosphere.

Keywords: Interplanetary turbulence, Interplanetary particle acceleration, Slow solar wind
Cosmological Constraints on Nonphantom Dynamical Dark Energy with DESI Data Release 2 Baryon Acoustic Oscillations: A 3σ+ Lensing Anomaly. We consider a 12-parameter cosmological model with nonphantom dynamical dark energy (NPDDE), where nonphantom implies that the equation of state (EoS) of dark energy (DE), w(z) ≥ −1 for all redshifts z. Thus, the DE-EoS covers the parameter space corresponding to the popular single scalar-field DE models, i.e., quintessence. The cosmological model comprises six parameters of the Λ-cold dark matter model, and additionally the dynamical DE EoS parameters (w0, wa), the scaling of the lensing amplitude (Alens), the sum of the neutrino masses (∑mν), the effective number of nonphoton relativistic degrees of freedom (Neff), and the running of the scalar spectral index (αs). We derive constraints on the parameters by combining the latest Dark Energy Spectroscopic Instrument Data Release (DR) 2 baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) power spectra from Planck Public Release (PR) 4, CMB lensing data from Planck PR4 and Atacama Cosmology Telescope DR6, uncalibrated Type Ia supernovae (SNe) data from the Pantheon+ and Dark Energy Survey (DES) Year 5 samples, and weak lensing (WL) data from DES Year 1. Our major finding is that with CMB+BAO+WL and CMB+BAO+SNe+WL, we find 3σ+ evidence for Alens &gt; 1 even with Planck PR4, indicating a higher than expected CMB lensing amplitude relative to the NPDDE prediction of unity. This implies that for cosmology to accommodate realistic quintessence-like DE models (as opposed to unrealistic phantom DE), one would also need to explain a relatively significant presence of the lensing anomaly.

Keywords: Dark energy, Cosmic microwave background radiation, Hubble constant, Type Ia supernovae, Cosmological neutrinos, Gravitational lensing shear, Baryon acoustic oscillations, Neutrino masses
Global Compressive Oscillations in the Outer Solar Corona Driven by an Extreme Coronal Mass Ejection. Coronal mass ejections are known drivers of large-scale waves in the low corona. However, wave dynamics in the extended corona and inner heliosphere remain largely unexplored. Here, we report the first observational and numerical evidence of coherent global compressive oscillations in the outer corona and inner heliosphere, revealed by white-light Solar and Heliospheric Observatory Large Angle and Spectrometric Coronagraph (LASCO) C3 data and an MHD simulation. Analyzing the coronal mass ejection event of 2012 July 23 using spectral proper orthogonal decomposition, we isolate two distinct wave signatures: (1) a directional fast-mode shock-like compressive wave that dissipates completely within 3 hr, and (2) a large-scale global circular wave front consistent with fast-mode MHD behavior, lasting 7 hr and extending across the LASCO C3 field of view, marking the first detection of such a global oscillation. Our findings reveal a previously unrecognized component of coronal mass ejection─driven wave activity, providing new constraints on the dynamics of the extended corona and inner heliosphere.

Keywords: Solar coronal waves, Solar coronal mass ejections, Heliosphere
XRISM Constraints on Unidentified X-Ray Emission Lines, Including the 3.5 keV Line, in the Stacked Spectrum of 10 Galaxy Clusters. We stack 3.75 Ms of early XRISM Resolve observations of 10 galaxy clusters to search for unidentified spectral lines in the E = 2.5─15 keV band (rest frame), including the E = 3.5 keV line reported in earlier low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3σ upper limit on the ms ∼ 7.1 keV DM particle decay rate (which corresponds to an E = 3.55 keV emission line) of Γ ∼ 1.0 × 10−27 s−1. This upper limit is 3─4 times lower than the one derived by Hitomi Collaboration from the Perseus observation but still 5 times higher than the XMM-Newton detection reported by E. Bulbul et al. in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations.

Keywords: Galaxy clusters, X-ray astronomy, Warm dark matter, X-ray sources, Intracluster medium, Dark matter
Only Nitrogen-enhanced Galaxies Have Detectable Ultraviolet Nitrogen Emission Lines at High Redshift. The detections of bright UV nitrogen emission lines in some high-redshift galaxies suggest unexpectedly high nitrogen-to-oxygen ratios ( log(N/O)≳−1.0 ) compared to local values ( log(N/O)≳−1.5 ) at similar metallicities ( 12+log(O/H)≲8.0 ). Although the presence of these "N-enhanced" galaxies indicates signatures of atypical chemical enrichment processes in the early Universe, the prevalence of nitrogen enhancement in high-z galaxies is unclear. So far, only ∼10 z &gt; 5 galaxies have nitrogen abundance measurements, and they all suggest elevated N/O ratios. Do all high-redshift galaxies exhibit elevated N/O ratios, or are we simply missing "N-normal" galaxies whose nitrogen abundances follow the local N/O scaling relation? To tackle these questions, we calculate the detection limits of UV N III] or N IV] lines in current JWST surveys CEERS and JADES, and compare them to predictions from both "N-enhanced" and "N-normal" active galactic nuclei (AGN) narrow-line region and H II region photoionization models. We find that CEERS can only detect galaxies with significant nitrogen enhancement ( log(N/O)≳−0.4 ), while JADES can only detect galaxies with moderately elevated N/O ratios compared to local values ( log(N/O)≳−1.0 ). Even for the deepest exposure in JADES, UV nitrogen lines produced by "N-normal" galaxies at z &gt; 5 are too faint and thus not detectable, making their nitrogen abundance unmeasurable. Our results suggest that the existing sample of galaxies with measurable nitrogen abundances at z ≳ 5 is incomplete and biased toward galaxies with significantly elevated N/O ratios. Deep ( texp∼40─500 hr) spectroscopic surveys will be crucial for building a complete sample to study nitrogen enrichment mechanisms in the early Universe.

Keywords: AGN host galaxies, Starburst galaxies, Interstellar abundances, Ultraviolet spectroscopy, James Webb Space Telescope