Sazuna/UAT_keywords huggingface dataset:
The Galactic Disk North–South Asymmetry in Metallicity May Be a New Tracer for the Disk Warp. Galactic disk warp has been widely characterized by stellar distributions and stellar kinematics but has not been traced by stellar chemistry. Here, we use a sample with over 170,000 red clump (RC) stars selected from LAMOST and APOGEE first to establish a correlation between the north–south asymmetry in metallicity ([Fe/H]) and the disk warp. Our results indicate that the height of the [Fe/H] midplane for the whole RC sample stars is accurately described as Zw = 0.017 (R ‑ 7.112)2 sin(ϕ ‑ 9.218). This morphology aligns closely with the warp traced by Cepheids, suggesting that the disk north–south asymmetry in [Fe/H] may serve as a new tracer for the Galactic warp. Our detailed analysis of the young/thin disk stars of this RC sample suggests that its warp is well modeled as Zw = 0.016 (R ‑ 6.507)2 sin(ϕ ‑ 4.240), indicating that the line of node of the Galactic warp is oriented at 4.240   degrees.

Keywords: Stellar kinematics, Stellar abundances, Milky Way disk, Galaxy structure
A Galactic-scale Magnetized Wind around a Normal Star-forming Galaxy. Galaxy formation theory identifies superwinds as a key regulator of star formation rates, galaxy growth, and chemical enrichment. Thermal and radiation pressure are known to drive galactic-scale winds in dusty starbursting galaxies (e.g., M82), but modern numerical simulations have recently highlighted that cosmic-ray (CR)–driven winds may be especially important in normal galaxies with modest star formation rate surface densities. However, CR-driven winds have yet to be conclusively observed—leaving significant uncertainty in their detailed microphysics. We present MeerKAT radio continuum and H I spectral-line observations of one such normal galaxy, NGC 1532; a nearby (D ~ 15 Mpc) and nearly edge-on (i ≳ 80°) spiral galaxy tidally interacting with its smaller elliptical companion, NGC 1531. We find magnetized, highly ordered radio-continuum loops extending ~10 kpc above and below the disk, visibly connecting discrete star-forming regions in the disk to the center. The deep MeerKAT H I observations place an upper limit on the column density of neutral gas coincident with the outflow of NH I ≲ 3 × 1019 cm‑2. Unlike previously observed outflows—for which ejected gas and dust can be traced across multiple wavelengths—the loops in NGC 1532 show no detectable signs of dust or gas coincident with the radio emission far from the disk. We explore multiple possible mechanisms for driving this magnetic wind and favor an explanation where CR pressure plays a significant role in launching these outflows.

Keywords: Radio continuum emission, Galactic winds, Cosmic rays
Metal Pollution in Sun-like Stars from Destruction of Ultra–short-period Planets. Chemical evidence indicates that an appreciable fraction of Sun-like stars have engulfed rocky planets during their main-sequence lifetimes. We investigate whether the tidal evolution and destruction of ultra–short-period planets (USPs) can explain this phenomenon. We develop a simple parameterized model for the formation and engulfment of USPs in a population of main-sequence stars. With this model, it is possible to reproduce both the observed occurrence rate of USPs and the frequency of planet-engulfing Sun-like stars for a reasonable range of USP formation rates and tidal decay lifetimes. Our results support a theory of USP formation through gradual inward migration over many gigayears and suggest that engulfment occurs ~0.1–1 Gyr after formation. This lifetime is set by tidal dissipation in the USP itself instead of the host star, due to the perturbing influence of external companions. If USP engulfment is the main source of pollution among Sun-like stars, we predict a correlation between pollution and compact multiplanet systems; some 5%–10% of polluted stars should have a transiting planet of mass ≳ 5M⊕ and period ~4–12 days. We also predict an anticorrelation between pollution and USP occurrence.

Keywords: Exoplanet dynamics, Star-planet interactions, Exoplanet tides, Extrasolar rocky planets
Early-time Millimeter Observations of the Nearby Type II SN 2024ggi. The short-lived ionized emission lines in early spectroscopy of the nearby Type II supernova SN 2024ggi signify the presence of dense circumstellar matter (CSM) close to its progenitor star. We proposed the Atacama Large Millimeter/submillimeter Array (ALMA) observations by its Director's Discretionary Time program to catch the potential synchrotron radiation associated with the ejecta–CSM interaction. Multiepoch observations were conducted using ALMA band 6 at +8, +13, and +17 days after the discovery. The data show nondetections at the position of SN 2024ggi with a 3σ upper limit of less than 0.15 mJy, corresponding to a luminosity of approximately 8 × 1024 erg s‑1 Hz‑1. In this paper, we leverage the nondetections to place constraints on the properties of CSM surrounding SN 2024ggi. We investigate both the Wind and Eruptive models for the radial distribution of CSM, assuming a constant mass-loss rate in the Wind model and a distance-variant mass-loss rate in the Eruptive model. The derived CSM distribution for the Wind model does not align with the early-time spectral features, while the ALMA observations suggest a mass-loss rate of ~5 × 10‑3M⊙ yr‑1 for the Eruptive model. Conducting multiepoch millimeter/submillimeter observations shortly after the explosion, with a cadence of a few days, could offer a promising opportunity to capture the observable signature of the Eruptive model.

Keywords: Core-collapse supernovae, Millimeter astronomy, Circumstellar matter, Radio continuum emission, Supernovae
Relativistic Electron Acceleration and the "Ankle" Spectral Feature in Earth's Magnetotail Reconnection. Electrons are accelerated to high, nonthermal energies during explosive energy-release events in space, such as magnetic reconnection. However, the properties and acceleration mechanisms of relativistic electrons directly associated with the reconnection X-line are not well understood. This study utilizes Magnetospheric Multiscale (MMS) measurements to analyze the flux and spectral features of subrelativistic to relativistic (∼80–560 keV) electrons during a magnetic reconnection event in Earth's magnetotail. This event provided a unique opportunity to measure the electrons directly energized by the X-line as MMS stayed in the separatrix layer, where the magnetic field directly connects to the X-line, for approximately half of the observation period. Our analysis revealed that the fluxes of relativistic electrons were clearly enhanced within the separatrix layer, and the highest flux was directed away from the X-line, which suggested that these electrons originated directly from the X-line. Spectral analysis showed that these relativistic electrons deviated from the main plasma sheet population and exhibited an "ankle" feature similar to that observed in galactic cosmic rays. The contribution of "ankle" electrons to the total electron energy density increased from 0.1% to 1% in the separatrix layer though the spectral slopes did not exhibit clear variations. Further analysis indicated that while these relativistic electrons originated from the X-line, they experienced a nonnegligible degree of scattering during transport. These findings provide clear evidence that magnetic reconnection in Earth's magnetotail can efficiently energize relativistic electrons directly at the X-line, providing new insights into the complex processes governing electron dynamics during magnetic reconnection.

Keywords: Planetary magnetospheres, Solar magnetic reconnection
The NANOGrav 15 yr Data Set: Running of the Spectral Index. The NANOGrav 15 yr data provide compelling evidence for a stochastic gravitational-wave (GW) background at nanohertz frequencies. The simplest model-independent approach to characterizing the frequency spectrum of this signal consists of a simple power-law fit involving two parameters: an amplitude A and a spectral index γ. In this Letter, we consider the next logical step beyond this minimal spectral model, allowing for a running (i.e., logarithmic frequency dependence) of the spectral index,  . We fit this running-power-law (RPL) model to the NANOGrav 15 yr data and perform a Bayesian model comparison with the minimal constant-power-law (CPL) model, which results in a 95% credible interval for the parameter β consistent with no running,  , and an inconclusive Bayes factor,  . We thus conclude that, at present, the minimal CPL model still suffices to adequately describe the NANOGrav signal; however, future data sets may well lead to a measurement of nonzero β. Finally, we interpret the RPL model as a description of primordial GWs generated during cosmic inflation, which allows us to combine our results with upper limits from Big Bang nucleosynthesis, the cosmic microwave background, and LIGO–Virgo–KAGRA.

Keywords: Cosmology, Bayesian statistics, Pulsar timing method, High energy astrophysics, Cosmic microwave background radiation, Cosmic inflation, Gravitational waves
The First JWST View of a 30-Myr-old Protoplanetary Disk Reveals a Late-stage Carbon-rich Phase. We present a JWST MIRI/MRS spectrum of the inner disk of WISE J044634.16–262756.1B (hereafter J0446B), an old (∼34 Myr) M4.5 star but with hints of ongoing accretion. The spectrum is molecule-rich and dominated by hydrocarbons. We detect 14 molecular species (H2, CH3, CH4, C2H2, 13CCH2, C2H4, C2H6, C3H4, C4H2, C6H6, HCN, HC3N, CO2, and 13CO2) and two atomic lines ([Ne II] and [Ar II]), all observed for the first time in a disk at this age. The detection of spatially unresolved H2 and Ne gas strongly supports that J0446B hosts a long-lived primordial disk, rather than a debris disk. The marginal H2O detection and the high C2H2/CO2 column density ratio indicate that the inner disk of J0446B has a very carbon-rich chemistry, with a gas-phase C/O ratio ≳2, consistent with what has been found in most primordial disks around similarly low-mass stars. In the absence of significant outer disk dust substructures, inner disks are expected to first become water-rich due to the rapid inward drift of icy pebbles and evolve into carbon-rich as outer disk gas flows inward on longer timescales. The faint millimeter emission in such low-mass star disks implies that they may have depleted their outer icy pebble reservoir early and already passed the water-rich phase. Models with pebble drift and volatile transport suggest that maintaining a carbon-rich chemistry for tens of Myr likely requires a slowly evolving disk with α-viscosity ≲10‑4. This study represents the first detailed characterization of disk gas at ∼30 Myr, strongly motivating further studies into the final stages of disk evolution.

Keywords: Infrared astronomy, Protoplanetary disks, Circumstellar disks, Astrochemistry
Helical Magnetic Field in a Massive Protostellar Jet. Highly collimated outflows (jets) are observed across a wide range of astrophysical systems involving the accretion of material onto central objects, from supermassive black holes in active galaxies to proto-brown dwarfs and stellar-mass black holes. Despite the diversity of their driving sources, it is believed that all jets are different manifestations of a single universal phenomenon. However, a unified explanation for their ejection and collimation remains elusive. In this study we present the first rotation measure analysis of the polarized synchrotron emission ever performed in a protostellar radio jet, which allows us to reveal its true 3D magnetic structure. Unlike extragalactic radio jets, which often exhibit faint counterjets, protostellar radio jets allow both the jet and the counterjet to be analyzed. This exceptional circumstance allows us to unveil the magnetic field structure of both components. Our findings provide the first solid evidence for a helical magnetic field within a protostellar jet, supporting the universality of the jet collimation mechanism.

Keywords: Interstellar magnetic fields, Protostars, Radio jets, Interstellar synchrotron emission
An Extreme Stellar Prominence Eruption Observed by LAMOST Time-domain Spectroscopy. We report the detection of an extreme stellar prominence eruption on the M dwarf Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) J044431.62+235627.9, observed through time-domain Hα spectroscopy with the LAMOST. This prominence eruption was accompanied by a superflare lasting over 160.4 minutes. The Hα line profile exhibits significant blue-wing enhancement during the impulsive phase and near the flare peak, with a projected bulk blueshift velocity of ‑228 ± 11 km s‑1 and a maximum blueshift velocity reaching ‑605 ± 15 km s‑1. Velocity analysis of the eruptive prominence at various heights above the stellar surface indicates that some of the projected ejection velocities along the line of sight exceed the corresponding escape velocities, suggesting a potential coronal mass ejection (CME). The equivalent width (EW) of the Hα blue-wing enhancement in this eruption appears to be the largest observed to date and is comparable to the EW of the Hα line profile during the quiescent phase of the host star. We performed a two-cloud modeling for the prominence and the associated flare, which suggests that the eruptive prominence has a mass ranging from 1.6 × 1019 to 7.2 × 1019 g. More importantly, the mass ratio of the erupting prominence to its host star is the largest among all reported stellar prominence eruptions/CMEs.

Keywords: Stellar coronal mass ejections, Stellar flares, Solar filament eruptions, Solar coronal mass ejections, Spectroscopy
Newest Measurements of Hubble Constant from DESI 2024 Baryon Acoustic Oscillation Observations. In this Letter, we use the latest results from the Dark Energy Spectroscopic Instrument (DESI) survey to measure the Hubble constant. Baryon acoustic oscillation (BAO) observations released by the DESI survey, allow us to determine H0 from the first principles. Our method is purely data-driven and relies on unanchored luminosity distances reconstructed from Type Ia supernovae (SN Ia) data and H(z) reconstruction from cosmic chronometers. Thus, it circumvents calibrations related to the value of the sound horizon size at the baryon drag epoch or intrinsic luminosity of SN Ia. We find  H0=68.4‑0.8+1.0kms‑1Mpc‑1  at a 68% confidence level, which provides the Hubble constant at an accuracy of 1.3% with minimal assumptions. Our assessments of this fundamental cosmological quantity using the BAO data spanning the redshift range z = 0.51–2.33 agree very well with Planck's results and TRGB results within 1σ. This result is still in a 4.3σ tension with the results of the Supernova H0 for the Equation of State.

Keywords: Hubble constant, Observational cosmology, Cosmological parameters
Radial Evolution of MHD Turbulence Anisotropy in Low Mach Number Solar Wind. The Parker Solar Probe (PSP) and Wind spacecraft observed the same plasma flow during PSP encounter 15. The solar wind evolves from a sub-Alfvénic flow at 0.08 au to become modestly super-Alfvénic at 1 au. We study the radial evolution of the turbulence properties and deduce the spectral anisotropy based on the nearly incompressible (NI) MHD theory. We find that the spectral index of the z+ spectrum remains unchanged (∼‑1.53), while the z‑ spectrum steepens, the index of which changes from ‑1.35 to ‑1.47. The fluctuating kinetic energy is on average greater than the fluctuating magnetic field energy in the sub-Alfvénic flow while smaller in the modestly super-Alfvénic flow. The NI MHD theory well interprets the observed Elsässer spectra. The contribution of 2D fluctuations is nonnegligible for the observed z‑ frequency spectra for both intervals. Particularly, the magnitudes of 2D and NI/slab fluctuations are comparable in the frequency domain for the modestly super-Alfvénic flow, resulting in a slightly concave shape of z‑ spectrum at 1 au. We show that, in the wavenumber domain, the power ratio of the observed forward NI/slab and 2D fluctuations is ∼15 at 0.08 au, while it decreases to ∼3 at 1 au, suggesting the growing significance of the 2D fluctuations as the turbulence evolves in low Mach number solar wind.

Keywords: Interplanetary turbulence, Solar physics, Solar wind, Solar corona
Longitudinal Dependence of Heavy Ion Composition in the 2021 October 28 Ground Level Enhancement Event. The 2021 October 28 solar energetic particle (SEP) event was a rare ground level enhancement (GLE) event, where secondary particles from the interactions of SEPs with the Earth's atmosphere were detected by neutron monitors on the ground. A number of papers have examined the solar signatures, neutron monitor observations, and the characteristics of the SEP protons and electrons for this event. Here we describe the heavy ion signatures, specifically O and Fe, observed by multiple spacecraft. Parker Solar Probe, Solar Terrestrial Relations Observatory-Ahead, and Advanced Composition Explorer were distributed over nearly 60° in solar longitude and 0.4 au in heliocentric distance. Despite their separations, all three spacecraft measured event-integrated O and Fe spectra, well represented by power laws, with nearly the same power-law index of approximately −1.7, which is significantly harder than most large SEP events and many GLE events. Moreover, the Fe/O abundance ratio determined from these spectra was also found to be spatially invariant over the 60° in longitude and 0.4 au in heliocentric distance. Such near uniformity is highly unusual, and only one similar occurrence was found in a previous multispacecraft. The observed Fe/O ratio of 0.39 is higher than typical for large SEP events but not unusual for GLE events.

Keywords: Solar energetic particles, Space weather, Solar coronal mass ejections, Heliosphere
Deep Learning the Forecast of Galactic Cosmic-Ray Spectra. We introduce a novel deep learning framework based on long short-term memory networks to predict galactic cosmic-ray spectra on a one-day-ahead basis by leveraging historical solar activity data, overcoming limitations inherent in traditional transport models. By flexibly incorporating multiple solar parameters, such as the heliospheric magnetic field, solar wind speed, and sunspot numbers, the model achieves accurate short-term and long-term predictions of cosmic-ray flux. The addition of historical cosmic-ray flux data significantly enhances prediction accuracy, allowing the model to capture complex dependencies between past and future flux variations. Additionally, the model reliably predicts full cosmic-ray spectra for different particle species, enhancing its utility for comprehensive space weather forecasting. Our approach offers a scalable, data-driven alternative to traditional physics-based methods, ensuring robust daily and long-term forecasts. This work opens avenues for advanced models that can integrate broader observational data, with significant implications for space weather monitoring and mission planning.

Keywords: Galactic cosmic rays, Solar wind, Heliosphere, Cosmic rays
The Discovery and Characterization of Minimoon 2024 PT<SUB>5</SUB>. Minimoons are asteroids that become temporarily captured by the Earth─Moon system. We present the discovery of 2024 PT5, a minimoon discovered by the Asteroid Terrestrial-impact Last Alert System Sutherland telescope on 2024 August 7. The minimoon with heliocentric semimajor axis, a ~ 1.01 au, and perihelion, q ~ 0.99 au, became captured by the Earth─Moon system on 2024 September 29 and left on 2024 November 25 UTC. Visible g, r, i, and Z spectrophotometry was obtained using Gemini North/Gemini Multi-Object Spectrograph on 2024 September 27. The color indices are g − r = 0.58 ± 0.04, r − i = 0.29 ± 0.04, and i − Z = −0.27 ± 0.06, and the spectrum best matches lunar rock samples followed by S-complex asteroids. Assuming an albedo of 0.21 and using our measured absolute magnitude of 28.64 ± 0.04, 2024 PT5 has a diameter of 5.4 ± 1.2 m. We also detect variations in the lightcurve of 2024 PT5 with a 0.28 ± 0.07 mag amplitude and a double-peaked period of ~2600 ± 500 s. We improve the orbital solution of 2024 PT5 with our astrometry and estimate the effect of radiation pressure on its deriving an area-to-mass ratio of 7.02 ± 2.05 × 10−5 m2 kg−1, implying a density of ~3.9 ± 2.1 g cm−3, compatible with having a rocky composition. If we assume 2024 PT5 is from the near-Earth object (NEO) population, its most likely sources are resonances in the inner Main Belt when we compare its orbit with the NEO population model though this does not exclude a lunar origin.

Keywords: Near-Earth objects, Small Solar System bodies
Gamma-Ray Bursts and Kilonovae from the Accretion-induced Collapse of White Dwarfs. We present the first seconds-long 2D general relativistic neutrino magnetohydrodynamic simulations of accretion-induced collapse (AIC) in rapidly rotating, strongly magnetized white dwarfs (WDs), which might originate as remnants of double-WD mergers. This study examines extreme combinations of magnetic fields and rotation rates, motivated both by the need to address the limitations of 2D axisymmetric simulations and to explore the physics of AIC under rare conditions that, while yet to be observationally confirmed, may be consistent with current theoretical models and account for unusual events. Under these assumptions, our results demonstrate that, if realizable, such systems can generate relativistic jets and neutron-rich outflows with properties consistent with long gamma-ray bursts (LGRBs) accompanied by kilonovae, such as GRB 211211A and GRB 230307A. These findings highlight the potential role of AIC in heavy r-process element production and offer a framework for understanding rare LGRBs associated with kilonova emission. Longer-duration 3D simulations are needed to fully capture magnetic field amplification, resolve instabilities, and determine the fate of the energy retained by the magnetar at the end of the simulations.

Keywords: Neutron stars, Gamma-ray bursts, Radiative magnetohydrodynamics, White dwarf stars, R-process, Light curves, Magnetars
MSA-3D: Metallicity Gradients in Galaxies at z ∼ 1 with JWST/NIRSpec Slit-stepping Spectroscopy. The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early Universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at 0.5 ≲ z ≲ 1.7 from the MSA-3D survey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST's diffraction limit and a high spectral resolution of R ≃ 2700. The metallicity gradients measured in our galaxy sample range from ‑0.03 to 0.02 dex kpc‑1. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient at z ∼ 1 with small intrinsic scatter of 0.02 dex kpc‑1. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more "disky." This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of the JWST NIRSpec microshutter assembly in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution.

Keywords: Star formation, Galactic abundances, High-redshift galaxies, Galaxy kinematics