Sazuna/UAT_keywords huggingface dataset:
Hot Spot Offset Variability from Magnetohydrodynamical Thermoresistive Instability in Hot Jupiters. Hot Jupiter (HJ) atmospheres are possibly subject to a thermoresistive instability (TRI). Such an instability may develop as the ohmic heating increases the electrical conductivity in a positive feedback loop, which ultimately leads to a runaway of the atmospheric temperature. We extend our previous axisymmetric one-dimensional radial model, by representing the temperature and magnetic diffusivity as a first-order Fourier expansion in longitude. This allows us to predict the hot spot offset during the rapid unfolding of the TRI and following Alfvénic oscillations. The instability is periodically triggered and damped within ≈10–40 days, depending on the magnetic field strength, with months of slow buildup between recurring bursts. We show a few representative simulations undergoing TRI, in which the peak flux offset varies between approximately ±60∘ on a timescale of a few days with potentially observable brightness variations. Therefore, this TRI could be an observable feature of HJs, given the right timing of observation and transit and the right planetary parameters.

Keywords: Magnetohydrodynamics, Exoplanet atmospheric dynamics, Exoplanet atmospheric variability, Atmospheric dynamics, Astrophysical fluid dynamics, Exoplanet atmospheres
Derivation and Application of a Scaling between Hinode/SP and SDO/HMI Vector Magnetic Fields to Improve Magnetic Field Extrapolations. Full-disk measurements of the solar magnetic field by the Helioseismic and Magnetic Imager (HMI) are often used for magnetic field extrapolations, but its limited spatial and spectral resolution can lead to significant errors. We compare HMI data with observations of NOAA 12104 by the Hinode Spectropolarimeter (SP) to derive a scaling curve for the magnetic field strength, B. The SP data in the Fe I lines at 630 nm were inverted with the SIR code. We find that the Milne–Eddington inversion of HMI underestimates B and the line-of-sight flux, Φ, in all granulation surroundings by an average factor of 4.5 in plage and 9.2 in the quiet Sun in comparison to the SP. The deviation is inversely proportional to the magnetic fill factor, f, in the SP results. We derived a correction curve to match the HMI B with the effective flux B f in the SP data that scaled HMI B up by 1.3 on average. A comparison of non-force-free field extrapolations over a larger field of view without and with the correction revealed minor changes in connectivity and a proportional scaling of electric currents and Lorentz force (∝B ∼ 1.3) and free energy (∝B2 ∼ 2). Magnetic field extrapolations of HMI vector data with large areas of plage and quiet Sun will underestimate the photospheric magnetic field strength by a factor of 5–10 and the coronal magnetic flux by at least a factor of 2. An HMI inversion including a fill factor would mitigate the problem.

Keywords: Spectropolarimetry, Solar photosphere
YOLOX-LS: Strong Gravitational Lenses Detection in the DECaLS with Deep Learning. The identification of strong gravitational lenses is essential to facilitate many studies in astronomy. The search for strong gravitational lenses has become more challenging because of their scientific value and their rarity. In this paper, we construct a data set for strong gravitational lensing searches that consist of known lenses and lens candidates from the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys (the DESI Legacy Imaging Surveys) and the Dark Energy Survey (DES) and non-lenses from the Legacy Surveys Data Release 9 (DR9). We apply the YOLOX algorithm as the basic framework and improve it by selecting the optimal optimizer, activation function, attention mechanism, and loss function. The improved YOLOX-LS algorithm achieves 97.87%, 97.51%, 0.97, 96.8%, and 53.1% in the evaluation metrics of precision, recall, F1 score, mean average precision (mAP)@0.5, and mAP@0.5:0.95, respectively. Compared with the YOLOX model, it improves by 0.63%, 0.26%, and 0.6% in the three metrics of precision, recall, and mAP@0.5, respectively. This paper presents the results of the trained YOLOX-LS algorithm applied to 4.75 million cutout images. These images are centered on the central source with magz ≤ 20 in the Dark Energy Camera Legacy Survey footprint from DESI DR9. Finally, we find 1697 lenses, including 303 known lenses or candidates, and 1394 new candidates, among which there are 102 high-quality candidates. This further verifies that the YOLOX-LS algorithm proposed in this paper can be effectively applied to the search for strong gravitational lenses. All visual results are displayed online at https://github.com/Young-mmm/YOLOX-LS.

Keywords: Strong gravitational lensing, Convolutional neural networks
The Rapid Formation of the Metal-poor Milky Way. Our understanding of the assembly timeline of the Milky Way has been transforming along with the dramatic increase in astrometric and spectroscopic data available over the past several years. Many substructures in chemo-dynamical space have been discovered and identified as the remnants of various galactic mergers. To investigate the timeline of these mergers, we select main-sequence turnoff and subgiant stars (MSTOs) from the H3 survey, finding members in seven metal-poor components of the halo: Gaia-Sausage/Enceladus (GSE), the Helmi Streams, Thamnos, Sequoia, Wukong/LMS-1, Arjuna, and I'itoi. We also select out a metal-poor in situ population to facilitate comparison to the evolution of the Milky Way itself at these early epochs. We fit individual isochrone ages to the MSTOs in each of these substructures and use the resulting age distributions to infer simple star formation histories (SFHs). For GSE, we resolve an extended SFH that truncates ≈10 Gyr ago, as well as a clear age–metallicity relation. From this age distribution and measured SFH we infer that GSE merged with the Milky Way at a time 9.5–10.2 Gyr ago, in agreement with previous estimates. We infer that the other mergers occurred at various times ranging from 9 to 13 Gyr ago, and that the metal-poor in situ Galaxy built up within only a few billion years. These results reinforce the emerging picture that both the disk and halo of the Milky Way experienced a rapid assembly.

Keywords: Galaxy formation, Milky Way formation, Stellar ages, Milky Way stellar halo, Galaxy evolution, Milky Way evolution, Milky Way Galaxy
No Need to Know: Toward Astrophysics-free Gravitational-wave Cosmology. Gravitational waves (GWs) from merging compact objects encode direct information about the luminosity distance to the binary. When paired with a redshift measurement, this enables standard-siren cosmology: a Hubble diagram can be constructed to directly probe the Universe's expansion. This can be done in the absence of electromagnetic measurements, as features in the mass distribution of GW sources provide self-calibrating redshift measurements without the need for a definite or probabilistic host galaxy association. This "spectral siren" technique has thus far only been applied with simple parametric representations of the mass distribution, and theoretical predictions for features in the mass distribution are commonly presumed to be fundamental to the measurement. However, the use of an inaccurate representation leads to biases in the cosmological inference, an acute problem given the current uncertainties in true source population. Furthermore, it is commonly presumed that the form of the mass distribution must be known a priori to obtain unbiased measurements of cosmological parameters in this fashion. Here, we demonstrate that spectral sirens can accurately infer cosmological parameters without such prior assumptions. We apply a flexible, nonparametric model for the mass distribution of compact binaries to a simulated catalog of 1000 GW signals, consistent with expectations for the next LIGO–Virgo–KAGRA observing run. We find that, despite our model's flexibility, both the source mass model and cosmological parameters are correctly reconstructed. We predict a 11.2%✎ measurement of H 0, keeping all other cosmological parameters fixed, and a 6.4%✎ measurement of H(z = 0.9)✎ when fitting for multiple cosmological parameters (1σ uncertainties). This astrophysically agnostic spectral siren technique will be essential to arrive at precise and unbiased cosmological constraints from GW source populations.

Keywords: Gravitational wave astronomy, Bayesian statistics, Hubble constant, Compact binary stars
Chemical Fingerprints of M Dwarfs: High-resolution Spectroscopy on 31 M Dwarfs with SPIRou. We extend the methodology introduced by F. Jahandar et al. to determine the effective temperature and chemical abundances of 31 slowly rotating solar neighborhood M dwarfs (M1–M5) using high-resolution spectra from CFHT/SPIRou. This group includes 10 M dwarfs in binary systems with FGK primaries of known metallicity from optical measurements. By testing our T eff method on various synthetic models, we find a consistent inherent synthetic uncertainty of ∼10 K at a signal-to-noise ratio greater than 100. Additionally, we find that our results align with interferometric measurements, showing a consistent residual of ‑29 ± 31 K. Taking the inherent uncertainties into account, we infer the T eff values of our targets and find an excellent agreement with previous optical and near-infrared studies. Our high-resolution chemical analysis examines hundreds of absorption lines using χ 2 minimization using PHOENIX-ACES stellar atmosphere models. We present elemental abundances for up to 10 different elements, including refractory elements such as Si, Mg, and Fe, which are important for modeling the interior structure of exoplanets. In binary systems, we find an average [Fe/H] of ‑0.15 ± 0.08 for M dwarfs, marginally lower than the reported metallicity of ‑0.06 ± 0.18 for the FGK primaries from A. W. Mann et al. We also observe slightly subsolar chemistry for various elements in our nonbinary M dwarfs, most notably for O, C, and K abundances. In particular, we find an average metallicity of ‑0.11 ± 0.16, lower but still consistent with the typical solar metallicity of FGK stars (e.g., [Fe/H] = 0.04 ± 0.20 from J. M. Brewer et al. 2016). This study highlights significant discrepancies in various major M dwarf surveys likely related to differences in the methodologies employed.

Keywords: M dwarf stars, High resolution spectroscopy, Late-type stars, Abundance ratios, Stellar abundances, Chemical abundances, Stellar classification, Atomic spectroscopy, Spectroscopy, Stellar spectral types, Metallicity
Spherical Accretion in the Schwarzschild Spacetime in the Newtonian Analogous Construct. The velocity-dependent Newtonian analogous potentials (NAPs) corresponding to general relativistic (GR) spacetimes accurately capture most of the relativistic features, including all classical tests of GR, effectively representing spacetime geometries in Newtonian terms. The NAP formulated by Tejeda &amp; Rosswog (TR13) for Schwarzschild spacetime has been applied to the standard thin accretion disk around a black hole (BH) as well as in the context of streamlines of noninteracting particles accreting onto a Schwarzschild BH, showing good agreement with the exact relativistic solutions. As a further application, here we explore the extent to which TR13 NAP could describe a transonic hydrodynamical spherical accretion flow in Schwarzschild spacetime within the framework of standard Newtonian hydrodynamics. Instead of obtaining a typical single "saddle-type" sonic transition, a "saddle–spiral pair" is produced, with the inner sonic point being an (unphysical) "spiral type" and the outer being a usual "saddle type." The Bondi accretion rate at outer sonic radii, however, remains consistent with that of the GR case. The primary reason for the deviation of our findings from the classical Bondi solution is likely due to the inconsistency between the Euler-type equation in the presence of velocity-dependent TR13 NAP within the standard Newtonian hydrodynamics framework, and the corresponding GR Euler equation, regardless of the fluid's energy. Our study suggests that a (modified) hydrodynamical formalism is needed to effectively implement such potentials in transonic accretion studies that align with the spirit of TR13 like NAP, while remaining consistent with the GR hydrodynamics. This could then essentially circumvent GR hydrodynamics or GR magnetohydrodynamics equations

Keywords: Accretion, Black hole physics, Bondi accretion, High energy astrophysics
The Deuterium Fractionation of NH<SUB>3</SUB> in Massive Star-forming Regions. Deuteration is sensitive to environmental conditions in star-forming regions. To investigate NH2D chemistry, we compared the spatial distribution of ortho-NH2D  , NH3(1,1), and NH3(2,2) in 12 late-stage massive star-forming regions. By averaging several pixels along the spatial slices of ortho-NH2D  , we obtained the deuterium fractionation of NH3. In seven targets, the deuterium fractionation of NH3 shows a decreasing trend with increasing rotational temperature. This trend is less clear in the remaining five sources, likely due to limited spatial resolution. However, when considering all 12 sources together, the anticorrelation between NH3 deuterium fractionation and rotational temperature becomes less significant, suggesting that other physical parameters may influence the fractionation. Additionally, we found that the region of highest deuterium fractionation of NH3 is offset from the NH3 peak in each source, likely because the temperature is higher near the NH3 peaks and NH2D may be depleted from the gas phase as the molecular cloud core evolves, as well as the increased release of CO from grains into the gas phase.

Keywords: Interstellar molecules, Massive stars, Interstellar abundances, Star formation
Dependence of SYMH Change Rate on Dynamic Pressure during the Main Phases of Storms: A Comparative Analysis of the 2024 May and 2003 November Superstorms. We denote the variation in the SYMH index during the main phase of a geomagnetic storm as ΔSYMH and the duration of the storm's main phase as Δt. The ratio ΔSYMH/Δt represents the averaged rate of change of the ring current throughout the main phase of the storm. We analyzed the ΔSYMH/Δt ratios during the main phases of the 2024 May superstorm (referred to as storm1) and the 2003 November superstorm (referred to as storm2), followed by a comparison of the solar wind parameters that significantly influenced the main phases of these two events. We discovered that the ΔSYMH/Δt ratio for storm1 exceeded that of storm2. Additionally, the time integral of the solar wind electric field during the main phase of storm1 was less than that of storm2, which suggests that ΔSYMH/Δt is not solely determined by the solar wind electric field. Our findings also indicated that the average dynamic pressure during the main phase of storm1 was larger than that of storm2, highlighting the significance of dynamic pressure as a key parameter in influencing the variation of the ring current during the main phase of a geomagnetic storm.

Keywords: Slow solar wind, Solar-terrestrial interactions, Space weather, Solar coronal mass ejections
Dwarf Galaxies with Radio-excess Active Galactic Nuclei in the Very Large Array Sky Survey. We present a systematic search for radio active galactic nuclei (AGNs) in dwarf galaxies using recent observations taken by the Very Large Array Sky Survey (VLASS). To select these objects, we first establish a criterion to identify radio-excess AGNs using the infrared-radio correlation parameter, q, that describes the tight relation between radio and IR emission in star-forming galaxies. We find a 2σ threshold of q &lt; 1.94 to select radio-excess AGNs, which is derived from a sample of ∼7000 galaxies across the full mass range in the NASA-Sloan Atlas that have radio and IR detections from VLASS and the Wide-Field Infrared Survey Explorer, respectively. We create catalogs of radio-excess AGNs and star-forming galaxies and make these available to the community. Applying our criterion to dwarf galaxies with stellar masses M ⋆ ≲ 3 × 109 M ⊙ and redshifts z ≤ 0.15, and carefully removing interlopers, we find 10 radio-excess AGNs with radio-optical positional offsets between ∼0″ and 2.'3 (0–2.7 kpc). Based on statistical arguments and emission line diagnostics, we expect the majority of these radio-excess AGNs to be associated with the dwarf host galaxies rather than background AGNs. Five of the objects have evidence for hosting AGNs at other wavelengths, and five objects are identified as AGNs in dwarf galaxies for the first time. We also identify eight variable radio sources in dwarf galaxies by comparing the VLASS epoch 1 and epoch 2 observations to Faint Images of the Radio Sky at Twenty-centimeters detections presented in A. E. Reines et al. (2020).

Keywords: AGN host galaxies, Intermediate-mass black holes, Very Large Array, Dwarf galaxies, Active galactic nuclei, Radio sources
H I Intensity Mapping Cross-correlation with Thermal Sunyaev─Zel'dovich Fluctuations: Forecasted Cosmological Parameter Estimation for FAST and Planck. The 21 cm emission from neutral hydrogen surveys holds great potential as a valuable method for exploring the large-scale structure (LSS) of the Universe. In this paper, we forecast for the cross-correlation between the thermal Sunyaev─Zel'dovich (SZ) fluctuations as probed by the Planck satellite and fluctuations in the H I brightness temperature as probed by the ground-based Five-hundred-meter Aperture Spherical Telescope to trace the connection between galaxy clusters and the H I LSS. Assuming that the measurement is limited by instrumental noise rather than by foreground, we estimate the potential detectability of the cross-correlation signal and the improvement in the measurement of the H I cosmic density, the hydrostatic mass bias parameter, and the universal pressure profile parameters. We obtain a constraint on the cosmic neutral hydrogen density parameter significantly to σ(ΩH I) = 1.0 × 10−6. We also find that the average halo masses contributing to the H I − y cross-power spectrum in the one-halo regime is ∼1.5 × 1014 M ⊙. Our results also show that the H I─SZ cross-correlation has great potential to probe the distribution of neutral hydrogen (H I) within halos at low redshift.

Keywords: Radio astronomy, Sunyaev-Zeldovich effect, H I line emission
Comparison of the Origin of Short Gamma-Ray Bursts with or without Extended Emission. The merger of compact binary stars produces short gamma-ray bursts (sGRBs), involving channels such as neutron star–neutron star (BNS) and neutron star–black hole (NS–BH). The association between sGRB 170817A and gravitational wave GW170817 provides reliable evidence for the BNS channel. Some speculations suggest that sGRBs with extended emission (EE) may represent another distinct population. The offset is the distance between the GRB sky localization and the host galaxy center. We compared the offset distributions of these two types of samples (46 sGRBs with EE and 9 without EE samples) and found that they follow the same distribution. Utilizing nonparametric methods, we examined the luminosity function and formation rate of sGRBs without any assumptions. The luminosity function can be described as   for   (  and for  ) for sGRBs without EE and   for   (  and for  ) for sGRBs with EE. The formation rate is characterized as ρ(z) ∝ (1 + z)‑3.04±0.10 for z &lt; 1 and as ρ(z) ∝ (1 + z)‑0.29±0.38 for 1 &lt; z &lt; 3 for sGRBs without EE, while for sGRBs with EE, it is ρ(z) ∝ (1 + z)‑3.85±0.15 for z &lt; 1 and ρ(z) ∝ (1 + z)‑0.40±1.11 for 1 &lt; z &lt; 3. Our findings suggest no significant difference in the progenitors of sGRBs with and without EE when considered in terms of spatial offsets, formation rates, and luminosity function.

Keywords: Gamma-ray bursts, Bayesian statistics, Compact objects
The Long-term Evolution of the Solar Transition Region. Long-term evolution characteristics of the solar transition region have been unclear. In this study, daily images of the solar full disk derived from the observations by the Solar Dynamics Observatory/Atmospheric Imaging Assembly at 304 Å wavelength from 2011 January 1 to 2022 December 31 are used to investigate the long-term evolution of the solar transition region. It is found that long-term variation in the transition region of the full disk is in phase with the solar activity cycle, and thus the polar brightening should occur in the maximum epoch of the solar cycle. Long-term variation of the background transition region is found to be likely in antiphase with the solar activity cycle at middle and low latitudes. The entire transition region, especially the active transition region is inferred to be mainly heated by the active-region magnetic fields and the ephemeral-region magnetic fields, while the quieter transition region is believed to be mainly heated by network magnetic fields. Long-term evolution characteristics of various types of the magnetic fields at the solar surface are highly consistent with these findings, and thus provide an explanation for them.

Keywords: Solar transition region
Constraining Anisotropic Diffusion between Geminga and Earth with the Cosmic-Ray Electron and Positron Spectrum. The gamma-ray halo around Geminga indicates significant suppression of cosmic-ray diffusion. One possible explanation for this phenomenon is the projection effect of slow diffusion perpendicular to the mean magnetic field (characterized by the diffusion coefficient D⊥) within an anisotropic diffusion framework. In this scenario, the diffusion coefficient parallel to the mean field (D∥) can still be large, enabling electrons and positrons (e±) produced by Geminga to efficiently travel to Earth along the magnetic field lines, possibly resulting in a detectable e± flux. In this work, we first determine the basic parameters of the anisotropic model using the morphology and spectral measurements of the Geminga halo and then predict the flux of e± produced by Geminga at the location of Earth. We find that the e‑ + e+ spectrum of DAMPE can give crucial constraint on the anisotropic diffusion model: to ensure that the predicted spectrum does not exceed the measurements, the Alfvén Mach number of the turbulent magnetic field (MA) should not be less than 0.75, corresponding to D∥/D⊥ ≲ 3 given that  D⊥=D∥MA4 . This implies that a significant suppression of D∥ relative to the average value in the Galaxy may still be necessary. Furthermore, we find that under the anisotropic diffusion model, Geminga can produce a very sharp feature around 1 TeV in the e‑ + e+ spectrum, which could naturally explain the peculiar 1.4 TeV excess tentatively observed by DAMPE.

Keywords: Pulsar wind nebulae, Magnetic fields, Interstellar medium, Cosmic rays