Sazuna/UAT_keywords huggingface dataset:
A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2. The transit method is currently one of our best means for the detection of potentially habitable "Earth-like" exoplanets. In principle, given sufficiently high photometric precision, cool Earth-sized exoplanets orbiting Sun-like stars could be discovered via single transit detections; however, this has not previously been achieved. In this work, we report a 10 hr long single transit event which occurred on the V = 10.1 K-dwarf HD 137010 during K2 Campaign 15 in 2017. This transit is comparatively shallow (225 ± 10 ppm) but is detected at high signal-to-noise thanks to the exceptionally high photometric precision achieved for the target. Our analysis of the K2 photometry, historical and new imaging observations, and archival radial velocities and astrometry strongly indicate that the event was astrophysical, occurred on-target, and can be best explained by a transiting planet candidate, which we designate HD 137010 b. The single observed transit implies a radius of  1.06−0.05+0.06R⊕ , and assuming negligible orbital eccentricity we estimate an orbital period of  355−59+200  days ( a=0.88−0.10+0.32  au), properties comparable to Earth. We project an incident flux of  0.29−0.13+0.11I⊕ , which would place HD 137010 b near the outer edge of the habitable zone. This is the first planet candidate with Earth-like radius and orbital properties transiting a Sun-like star bright enough for substantial follow-up observations.

Keywords: Extrasolar rocky planets, Exoplanets, Exoplanet astronomy, Exoplanet detection methods, Transit photometry, Habitable zone
Hour-scale Variations of Water Molecules in the Lunar Soil Revealed by Chang'e-6 In Situ Observations. The speciation, inventory, and dynamic changes of water (OH/H2O) on the lunar surface remain poorly constrained. The Chang'e-6 (CE-6) mission conducted in situ spectroscopic measurements of lunar water over time intervals shorter than one lunar local hour (10:00─11:00 a.m.). By integrating spectral analysis with quantitative water content estimation, we provide compelling evidence for two distinct water reservoirs: adsorbed molecular water (H2O) on the surfaces of soil grains, and hydroxyl (OH) groups incorporated within the crystal lattices of minerals. The in situ observations further document the gradual loss of water molecules (up to 48 ppm) until near exhaustion over an hourly time scale on the lunar surface. For the first time, we calculated the apparent desorption activation energy (Ed = 1.23─1.26 eV) of water molecules based on in situ measurements, which is consistent with observations from the Lyman Alpha Mapping Project spectrometer and results from laboratory experiments. These water molecules are inferred to originate from solar wind proton (H+) implantation, forming via recombinative desorption of chemically bound OH in lunar minerals and glasses. This study constitutes a significant advance toward elucidating lunar water dynamics and provides critical parameters for modeling the lunar water cycle.

Keywords: Lunar surface, The Moon, Lunar mineralogy, Lunar science
Extreme Winds on the Emerging Dayside of an Ultrahot Jupiter. High-resolution spectroscopy provides a unique opportunity to directly probe atmospheric dynamics by resolving Doppler shifts of planetary signals as a function of orbital phase. Using the optical spectrometer the Keck Planet Finder, we carry out a pilot study on high-resolution phase-curve spectra of the ultrahot Jupiter KELT-9 b. We spectrally and temporally resolve its dayside emission from posttransit to preeclipse (orbital phase ϕ = 0.1─0.45). The signal strength and width increase with orbital phase as the dayside rotates into view. The net Doppler shift varies progressively from −13.4 ± 0.6 to −0.4 ± 1.0 km s−1, the extent of which exceeds its rotation velocity of 6.4 ± 0.1 km s−1, providing unambiguous evidence of atmospheric winds. We devise a retrieval framework to fit the full time-series spectra, accounting for the variation of the line profiles due to the rotation and winds. We retrieve a supersonic day-to-night wind speed up to 11.7 ± 0.6 km s−1 on the emerging dayside, representing the most extreme atmospheric winds in hot Jupiters to date. Comparison to 3D circulation models reveals weak atmospheric drag, consistent with relatively efficient heat recirculation, as also supported by space-based phase-curve measurements. Additionally, we retrieve the dayside chemistry (including Fe I, Fe II, Ti I, Ti II, Ca I, Ca II, Mg I, and Si I) and temperature structure, and we place constraints on the nightside thermal profile. Our high-resolution phase-curve spectra and the measured supersonic winds provide excellent benchmarks for extreme physics in circulation models, demonstrating the power of this technique in understanding the climates of hot Jupiters.

Keywords: Exoplanet atmospheric dynamics, High resolution spectroscopy, Exoplanet atmospheres
Double Hot Jupiter Formation through Mirrored ZLK Migration in Binary Star Systems: The Case of WASP-94. To date, only a handful of binary star systems are known with at least one confirmed planet orbiting each star. Such systems, however, offer a unique perspective on the stochasticity intrinsic to planet formation and evolution—particularly in twin binary star systems, which consist of near-equal-mass stars formed contemporaneously in the same birth environment. The WASP-94 system, which includes twin F-type stars, is a striking exemplar of such systems, containing two hot Jupiters: WASP-94 Ab is a transiting, spin─orbit misaligned giant planet with a 4 day orbital period, while WASP-94 Bb is nontransiting and has a tighter 2 day orbital period. In this work, we leverage N-body simulations to show that the current double hot Jupiter configuration of the WASP-94 system can be reproduced through mirrored von Zeipel─Lidov─Kozai migration. The upcoming Gaia astrometric data releases offer the potential to search for additional twin planetary systems, including double cold Jupiter systems that may serve as the progenitors for WASP-94-like configurations.

Keywords: Exoplanet dynamics, Exoplanet migration, Binary stars, Hot Jupiters, Exoplanets, Exoplanet systems, Exoplanet astronomy, Exoplanet evolution
Characterizing Alfvénicity and Proton Temperature Distributions in Interplanetary Coronal Mass Ejection Magnetic Clouds. We investigated a comprehensive sample of 474 interplanetary coronal mass ejection (ICME) events observed by the Wind spacecraft to examine the Alfvénic characteristics within their magnetic cloud regions. The analysis focuses on identifying inward and outward Alfvénic fluctuations of the magnetic and velocity field components. Our results reveal that approximately 74.68% of ICME magnetic cloud regions are non-Alfvénic, while 25.32% exhibit clear Alfvénic signatures, predominantly characterized by outward fluctuations. Furthermore, the temperature distribution shows a substantial enhancement in Alfvénic regions compared to non-Alfvénic ones, with proton temperatures elevated up to ∼33 eV. These findings suggest that Alfvénic fluctuations may play a significant role in the localized plasma heating within ICME structures and provide potential constraints on their broader contribution to space plasma environments.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Alfven waves
Dark-matter-deficient Galaxies from Collisions: A New Probe of Bursty Feedback and Dark Matter Physics. High-velocity collisions between gas-rich ultradiffuse galaxies present a promising formation channel for dark-matter-deficient galaxies (DMDGs). Using hydrodynamical simulations, we show that the progenitors' baryonic binding energy, ∣Ebind∣, critically controls the outcome. Repeated potential fluctuations, e.g., from bursty feedback, inject energy and reduce ∣Ebind∣ by ≍15%, yielding fewer but substantially more massive DMDGs. By contrast, elastic self-interacting dark matter (SIDM) produces comparable cores without lowering ∣Ebind∣, perturbing DMDG masses without clear enhancement. This differs from what happens in host halos, where SIDM-induced cores enhance dark matter tidal stripping while keeping baryons compact and resilient to tidal effects. The contrasting roles of SIDM may provide a means to distinguish feedback-formed halo cores from those created by SIDM. Among 15 paired simulation runs, 13 show higher DMDG masses in the weakened-binding case, and about two-thirds exhibit &gt;100% mass enhancements. The simulations also predict systematically lower gas fractions due to sustained postcollision star formation, yielding a clean observational signature. Upcoming wide-field imaging (CSST, LSST), HI surveys (FAST), and kinematic follow-up will be crucial to test this scenario.

Keywords: Hydrodynamical simulations, Galaxy formation, Stellar feedback, Dark matter, Galaxy evolution, N-body simulations
CECILIA: Gas-phase Physical Conditions and Multielement Chemistry at Cosmic Noon. Galaxies at Cosmic Noon (z ∼ 2─3) are characterized by rapid star formation that will lead to significant metal enrichment in the interstellar medium (ISM). While much observational evidence suggests that these galaxies are chemically distinct from those in the local Universe, directly measuring the ISM chemistry in large samples of high-z galaxies is only now possible with the observational capabilities of JWST. In this first key paper of the CECILIA program, we present the direct-method physical conditions and multielement abundances in 20 galaxies at Cosmic Noon. Using a combination of archival Keck/MOSFIRE and new ∼30 hr NIRSpec spectroscopy, we measure multiple electron gas densities and the temperature structure from the O+ and S2+ ions. We find that ne[O II] and ne[S II] are comparable but elevated with respect to ne in local star-forming galaxies, and the simultaneous Te[O II] and Te[S III] generally agree with photoionization model Te scaling relations. The O abundances in the CECILIA galaxies range from 12 + log(O/H) = 7.76 to 8.81 (12%─131% solar O/H), representing some of the highest direct-method metallicities and lowest Te (Te[O II] ≍ 6500 K) measured with JWST to date. The CECILIA galaxies exhibit significantly subsolar S/O and Ar/O, a signature of predominant enrichment from core-collapse supernovae. The N/O─O/H trends in the CECILIA galaxies generally agree with the abundance trends in local nebulae, but the large scatter in N/O could be sensitive to the star formation history. The CECILIA observations demonstrate that exceptionally deep JWST spectroscopy can unveil the multielement ISM abundance patterns in typical high-z galaxies.

Keywords: Interstellar medium, High-redshift galaxies, Chemical abundances, Emission line galaxies
On the Ultralong Gamma-Ray Transient GRB 250702B/EP 250702a. GRB 250702B/EP 250702a is an interesting long-duration gamma-ray transient whose nature is in debate. To obtain a full picture in the gamma-ray band, we implement a comprehensive targeted search of burst emission in a wide window of 30 days jointly with Insight-HXMT, GECAM, and Fermi Gamma-ray Burst Monitor data within the ETJASMIN framework. In the gamma-ray band, we find that there is a 50 s precursor about 25 hr before the 4 hr main burst, which generally consists of four emission episodes. Remarkably, we find that the soft X-ray emission after the main burst decays as a power law with a start time aligning with the last episode of main emission and an index of −5/3, which is perfectly consistent with the canonical prediction of fallback accretion. We conclude that the properties of the precursor, the main burst, and the following soft X-ray emission strongly support the ultralong gamma-ray burst (ULGRB) scenario, and all this gamma-ray and soft X-ray emission probably originates from a relativistic jet whose luminosity is dominated by the fallback accretion rate during the death collapse of a supergiant star.

Keywords: X-ray transient sources, Tidal disruption, Gamma-ray bursts
Using Gravity as an Age Indicator for Young Stars. The age of a young star is difficult to measure and yet is a fundamental property that is essential for understanding stellar evolution. Accurate age indicators across the early phases of low-mass stars are scarce and often rely on properties of the circumstellar environment. We investigate stellar surface gravity as a practical age estimator from the class I to the class III phases of low-mass stars. Gravity increases monotonically as young stars descend their Hayashi tracks. Gravity is a physical property of the central star and is independent of the circumstellar environment or evolutionary models. Also, gravity can be measured for individual objects. We performed two tests for the reliability of gravity as an age indicator: (1) the relative ages of the components of young binary stars and (2) the relative ages of a young moving group. We show that young binary stars have consistent gravities, as expected, if they are coeval. Similarly, we find similar gravities among the TW Hya group and derive a median age of 12.8 ± 1.2 Myr. In both cases, differences in gravities may reflect real differences in the ages. We show that there is no correlation between veiling emission and gravity, showing that circumstellar disk emission does not affect our ability to infer ages from measurements of photospheric stellar gravity.

Keywords: Stellar ages, Star formation, Stellar properties
exoALMA. XIX. Confirmation of Non-thermal Line Broadening in the DM Tau Protoplanetary Disk. Turbulence is expected to transport angular momentum and drive mass accretion in protoplanetary disks. One way to directly measure turbulent motion in disks is through molecular line broadening. DM Tau is one of only a few disks with claimed detection of nonthermal line broadening of 0.25cs─0.33cs, where cs is the sound speed. Using the radiative transfer code MCFOST within a Bayesian inference framework that evaluates over five million disk models to efficiently sample the parameter space, we fit high-resolution ( 0.″15 , 28 m s−1) 12CO J = 3─2 observations of DM Tau from the exoALMA Large Program. This approach enables us to simultaneously constrain the disk structure and kinematics, revealing a significant nonthermal contribution to the line width of ∼0.4cs, inconsistent with purely thermal motions. Using the CO-based disk structure as a starting point, we reproduce the CS J = 7─6 emission well, demonstrating that the CS (which is more sensitive to nonthermal motions than CO) agrees with the turbulence inferred from the CO fit. Establishing a well-constrained background disk model further allows us to identify residual structures in the moment maps that deviate from the expected emission, revealing localized perturbations that may trace forming planets. This framework provides a powerful general approach for extracting disk structure and nonthermal broadening directly from molecular line data and can be applied to other disks with high-quality observations.

Keywords: T Tauri stars, Protoplanetary disks, High angular resolution, CO line emission
IK Pegasi and the Double-merger Path to Type Ia Supernovae. Recent Gaia astrometry has revealed thousands of main-sequence + white dwarf (MS+WD) binaries at separations of ∼0.1─10 au, including a subset hosting unusually massive (≳0.8M⊙) WDs. We argue that s-process enrichment in the nondegenerate companion provides a powerful diagnostic for identifying WDs that formed via mergers in hierarchical triple systems. For a massive WD, standard single-star evolution requires a massive (≳4M⊙) progenitor, yet such progenitors produce negligible s-process yields. We define IK Peg─type systems as those exhibiting this mass─yield tension—barium-enhanced companions orbiting WDs too massive to have descended from efficient s-process producers. The well-known system IK Pegasi (IK Peg) exemplifies this class. Applying this framework to published spectroscopic data reveals several additional candidates, and we estimate that a few dozen such systems should exist in the current Gaia sample. If these systems trace inner-binary mergers in primordial triples, they represent observable intermediate stages toward eventual type Ia supernovae via the double-merger pathway, as predicted by recent population synthesis models.

Keywords: Post-asymptotic giant branch stars, Binary stars, Stellar mergers, White dwarf stars, Type Ia supernovae, Stellar evolution
Composition and Space-weathering Characteristics of the Tianwen-2 Mission's First Target: Near-Earth Asteroid (469219) Kamo'oalewa. The near-Earth asteroid Kamo'oalewa, a quasi-satellite of the Earth and the first target for sample return by China's Tianwen-2 mission, exhibits distinctive spectral characteristics. This study reanalyzes the visible and near-infrared reflectance spectrum of Kamo'oalewa published by B. N. L. Sharkey et al. This study analyzes the visible and near-infrared reflectance spectrum of Kamo'oalewa, obtained using the Large Binocular Telescope, to infer its mineral composition and space-weathering characteristics. Spectral similarity analysis is performed, by comparing the spectrum of Kamo'oalewa to mean spectra of various types in the Bus─DeMeo taxonomy, to make a preliminary constraint on the combined characteristics of surface mineralogy and space-weathering effects. To further characterize the mineral composition, a detailed analysis of the 1 μm band center is conducted, based on spectral data below 1.25 μm that have higher signal-to-noise ratios and more bands. Empirical models for normalized spectra are developed to estimate the Is/FeO content. The results suggest that asteroid Kamo'oalewa has a higher olivine abundance than typical S-type asteroids and the Moon, exhibiting an immature to submature degree of space weathering. These findings enhance our understanding of the evolution of similar quasi-satellites and provide important implication for the future explorations of the Tianwen-2 mission.

Keywords: Asteroids, Surface processes, Surface composition, The Moon, Spectroscopy, Asteroid surfaces
Extreme-ultraviolet Synthesis of Nanojet-like Ejections due to Coalescing Flux Ropes. Detection and characterization of small-scale energetic events such as nanoflares and nanojets remain challenging owing to their short lifetimes, small spatial extent, and relatively low energy release, despite their potential role in coronal heating. Recent observations have identified nanojets as small-scale (length ≲6.6 Mm, width ≲1 Mm), fast (∼ few 100 km s−1), and short-lived (≲30 s) ejections associated with nanoflare-scale energies, providing evidence of magnetic reconnection at small spatial scales. However, the lack of synthetic diagnostics has limited the connection between magnetohydrodynamic (MHD) models and observations. In this Letter, we present synthetic observations of the coalescence of two flux ropes, leading to nanojet-like signatures from a numerical model obtained with the MPI-AMRVAC code. We report synthetic observables in extreme-ultraviolet lines compatible with existing instruments such as Solar Dynamics Observatory/Atmospheric Imaging Assembly and the upcoming Multi-slit Solar Explorer mission and compare the synthetic observables with an existing observation of nanojets. The synthetic diagnostics of the emissivity maps, Doppler velocity, and thermal and nonthermal line broadening produce key observational properties, suggesting a plausible 3D scenario for nanojet generation where tiny flux ropes reconnect within loops. Our results provide predictions for the detectability of nanojets with current and future spectroscopic facilities and establish a bridge between MHD modeling and observations.

Keywords: Magnetohydrodynamics, Solar extreme ultraviolet emission, Solar corona, Solar magnetic reconnection
A τ─DM Relation for Fast Radio Burst Hosts?. It has been proposed that measurements of scattering times (τ) from fast radio bursts (FRBs) may be used to infer the FRB host dispersion measure (DM) and its redshift. This approach relies on the existence of a correlation between τ and DM within FRB hosts such as that observed for Galactic pulsars. We assess the measurability of a τ─DMhost relation through simulated observations of FRBs within the Australian Square Kilometre Array Pathfinder (ASKAP)/Commensal Real-time ASKAP Fast Transients (CRAFT) survey, taking into account instrumental effects. We show that even when the FRB hosts intrinsically follow the τ─DM relation measured for pulsars, this correlation cannot be inferred from FRB observations; this limitation arises mostly from the large variance around the average cosmic DM value given by the Macquart relation, the variance within the τ─DM relation itself, and observational biases against large τ values. We argue that theoretical relations have little utility as priors on redshift, e.g., for purposes of galaxy identification, and that the recent lack of an observed correlation between scattering and DM in the ASKAP/CRAFT survey is not unexpected, even if our understanding of a τ─DMhost relation is correct.

Keywords: Radio bursts
Machine Learning versus Spectral Energy Distribution Fitting: A Comparative Analysis of Accuracy in Stellar Mass Estimation. Traditional spectral energy distribution (SED)─fitting methods for stellar mass estimation face persistent challenges including systematic biases and computational constraints. We present a controlled comparison of machine learning (ML) and SED-fitting methods, assessing their accuracy, robustness, and computational efficiency. Using a sample of COSMOS-like galaxies from the Horizon-Active Galactic Nucleus (AGN) simulation as a benchmark with known true masses, we evaluate the parametric t-distributed stochastic neighbor embedding (Pt-SNE) algorithm trained on noise-injected G. Bruzual &amp; S. Charlot models against the established SED-fitting code LePhare. Our results demonstrate that Pt-SNE achieves superior accuracy, with an rms error (σF) of 0.169 dex compared to LePhare's 0.306 dex. Crucially, Pt-SNE exhibits significantly lower bias (0.029 dex) compared to LePhare (0.286 dex). Pt-SNE also shows greater robustness across all stellar mass ranges, particularly for low-mass galaxies (109─1010 M⊙), where it reduces errors by 47%─53%. Even when restricted to only six optical bands, Pt-SNE outperforms LePhare using all 26 available photometric bands, underscoring its superior informational efficiency. Computationally, Pt-SNE processes large data sets ∼3.2 × 103 times faster than LePhare. These findings highlight the fundamental advantages of ML methods for stellar mass estimation, demonstrating their potential to deliver more accurate, stable, and scalable measurements for large-scale galaxy surveys.

Keywords: Galaxy masses, Galaxy photometry, Galaxies
The Proper Motion of Draco II with HST Using Multiple Reference Frames and Methodologies. We present proper motion (PM) measurements for Draco II, an ultrafaint dwarf satellite of the Milky Way. These PMs are measured using two epochs of Hubble Space Telescope (HST)/Advanced Camera for Surveys imaging separated by a 7 yr temporal baseline. Measuring the PMs of low-luminosity systems is difficult due to the low number of member stars, requiring a precise inertial reference frame. We construct reference frames using three different sets of external sources: (1) stars with Gaia Data Release 3 data, (2) stationary background galaxies, and (3) a combination of the two. We show that all three reference frames give consistent PM results. We find that for this sparse, low-luminosity regime including background galaxies into the reference frame improves our measurement by up to ∼2× versus using only Gaia astrometric data. Using 301 background galaxies as a reference frame, we find that Draco II's systemic PM is  (μα*,μδ)=(1.043±0.029,0.879±0.028)  mas yr−1, which is the most precise measurement of the three we present in this paper.

Keywords: Local Group, Proper motions, Dwarf spheroidal galaxies