Sazuna/UAT_keywords huggingface dataset:
Calibration of Complementary Metal-oxide-semiconductor Sensor–based Photometry to a Few-millimagnitude Precision: The Case of the Mini-SiTian Array. We present a pioneering achievement in the high-precision photometric calibration of CMOS-based photometry, by application of the Gaia Blue Photometer or Red Photometer (XP) spectra–based synthetic photometry method to the mini-SiTian array (MST) photometry. Through 79 repeated observations of the f02 field on the night, we find good internal consistency in the calibrated MST GMST-band magnitudes for relatively bright stars, with a precision of about 4 mmag for GMST ∼ 13. Results from more than 30 different nights (over 3100 observations) further confirm this internal consistency, indicating that the 4 mmag precision is stable and achievable over timescales of months. An independent external validation using spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR10 and high-precision photometric data using CCDs from Gaia DR3 reveals a zero-point consistency better than 1 mmag. Our results clearly demonstrate that CMOS photometry is on par with CCD photometry for high-precision results, highlighting the significant capabilities of CMOS cameras in astronomical observations, especially for large-scale telescope survey arrays.

Keywords: Stellar photometry, Astronomy data analysis
First-principles Measurement of Ion and Electron Energization in Collisionless Accretion Flows. We present the largest 3D particle-in-cell shearing-box simulations of turbulence driven by the magnetorotational instability, for the first time employing the realistic proton-to-electron mass ratio. We investigate the energy partition between relativistically hot electrons and subrelativistic ions in turbulent accreting plasma, a regime relevant to collisionless, radiatively inefficient accretion flows around supermassive black holes such as those targeted by the Event Horizon Telescope. We provide a simple empirical formula to describe the measured heating ratio between ions and electrons, which can be used for more accurate global modeling of accretion flows with standard fluid approaches such as general-relativistic magnetohydrodynamics.

Keywords: Accretion, Supermassive black holes, Plasma physics, Plasma astrophysics, Astronomical simulations
The Large-scale Structure Supplies the Formation of Gas-star Misaligned Galaxies. Using the integral field unit data from the Mapping Nearby Galaxies at Apache Point Observatory survey, we build a sample of gas-star misaligned galaxies. The large-scale environment of misaligned galaxies is dominated by filaments and clusters, while it is less dense relative to the gas-star aligned control galaxies. The direction of the large-scale structure (LSS) is defined by its minor axis ( ), which indicates the slowest collapsing direction. For the aligned controls, the gas and stellar spins are preferentially perpendicular to  , since these galaxies reside in high-mass host halos. For the misaligned galaxies, the gas spins also tend to be perpendicular to  , suggesting that misaligned gas is recently accreted from the LSS. Meanwhile, there is no correlation between their stellar spins and  . There are two possible explanations for this observational phenomenon: (1) the large-scale environments of misaligned galaxies evolve as they grow, with stellar angular momenta acquired in different environments having different orientations; (2) the correlation between stellar spins and the LSS is smeared out since a relatively higher portion of misaligned galaxies in sheet environments are statistically analyzed together with those in filament environments.

Keywords: Galaxy kinematics, Galaxy evolution
Upper Limits on the Mass of Cool Gas in the Circumgalactic Medium of Dwarf Galaxies. We use H I absorption measurements to constrain the amount of cool (≈104 K), photoionized gas in the circumgalactic medium (CGM) of dwarf galaxies with M* = 106.5‑9.5 M⊙ in the nearby Universe (z &lt; 0.3). We show analytically that volume-filling gas gives an upper limit on the gas mass needed to reproduce a given H I column density profile. We introduce a power-law density profile for the gas distribution and fit our model to archival H I observations to infer the cool CGM gas mass, McCGM, as a function of halo mass. For volume-filling (fV = 1) models, we find McCGM = 5 × 108–2 × 109 M⊙, constituting ≲10% of the halo baryon budget. For clumpy gas, with fV = 0.01, the masses are a factor of ≈11 lower, in agreement with our analytic approximation. Our assumption that the measured H I forms entirely in the cool CGM provides a conservative upper limit on McCGM, and possible contributions from the intergalactic medium or warm/hot CGM will further strengthen our result. We estimate the mass uncertainties due to the range of redshifts in our sample and the unknown gas metallicity to be ≈15% and ≈10%, respectively. Our results show that dwarf galaxies have only ≲15% of their baryon budget in stars and the cool CGM, with the rest residing in the warm/hot CGM or ejected from the dark matter halos.

Keywords: Dwarf galaxies, Galaxy evolution, Circumgalactic medium
Self-consistent Multidimensional Penrose Process Driven by Magnetic Reconnection. Astronomical observations and numerical simulations are providing increasing evidence that resistive effects in plasmas around black holes (BHs) play an important role in determining the phenomenology observed from these objects. In this spirit, we present a general approach to the study of a Penrose process driven by plasmoids that are produced at reconnection sites along current sheets. Our formalism is meant to determine the physical conditions that make a plasmoid-driven Penrose process energetically viable, and can be applied to scenarios that are dominated by matter or magnetic field, that is, in magnetohydrodynamical or force-free descriptions. By exploring reconnection from an axisymmetric but curved surface, our approach can be considered genuinely multidimensional and allows us to explore conditions that are beyond the ones explored so far and that have been restricted to the equatorial plane. Furthermore, it provides a direct contact with numerical simulations of accretion onto BHs, which exhibit an intense reconnection activity outside the equatorial plane. Finally, to describe the kinematics of the plasma self-consistently, we use the well-known configuration of an equilibrium torus with a purely toroidal magnetic field. For such a torus, we discuss the existence of an "ergobelt," i.e., a nontrivial surface penetrating the ergosphere and acting as a natural site for the occurrence of reconnection, and from where we estimate the energetics of a plasmoid-driven Penrose process.

Keywords: Black hole physics, Magnetohydrodynamics, Black holes, High energy astrophysics, Kerr black holes, Plasma astrophysics, Penrose process, Magnetic fields, Rotating black holes, Classical black holes, Ergosphere, Astrophysical black holes
Spectropolarimetry of SN 2023ixf Reveals Both Circumstellar Material and an Aspherical Helium Core. We present multi-epoch optical spectropolarimetric and imaging polarimetric observations of the nearby Type II supernova (SN) 2023ixf discovered in M101 at a distance of 6.85 Mpc. The first imaging polarimetric observations were taken +2.33 days (60085.08 MJD) after the explosion, while the last imaging polarimetric data points (+73.19 and +76.19 days) were acquired after the fall from the light-curve plateau. At +2.33 days there is strong evidence of circumstellar material (CSM) interaction in the spectra and the light curve. A significant level of intrinsic polarization pr = 1.02% ± 0.07% is seen during this phase, which indicates that this CSM is aspherical. We find that the polarization evolves with time toward the interstellar polarization level during the photospheric phase, which suggests that the recombination photosphere is spherically symmetric. There is a jump in polarization (pr = 0.45% ± 0.08% and pr = 0.62% ± 0.08%) at +73.19 and +76.19 days when the light curve falls from the plateau. This is a phase where polarimetric data are sensitive to nonspherical inner ejecta or a decrease in optical depth into the single-scattering regime. We also present spectropolarimetric data that reveal line (de)polarization during most of the observed epochs. In addition, at +14.50 days we see an "inverse P Cygni" profile in the H and He line polarization, which clearly indicates the presence of asymmetrically distributed material overlying the photosphere. The overall temporal evolution of the polarization is typical for Type II SNe, but the high level of polarization during the rising phase has only been observed in SN 2023ixf.

Keywords: Spectropolarimetry, Red supergiant stars, Core-collapse supernovae, Type II supernovae, Stellar mass loss, Circumstellar matter, Polarimetry
Broadband γ-Ray Spectrum of Supernova Remnant Cassiopeia A. The core-collapse supernova remnant (SNR) Cassiopeia A (Cas A) is one of the brightest galactic radio sources with an angular radius of  . Although no extension of this source has been detected in the γ-ray band, using more than 1000 days of LHAASO data above ∼0.8 TeV, we find that its spectrum is significantly softer than those obtained with Imaging Air Cherenkov Telescopes (IACTs), and its flux near ∼1 TeV is about 2 times higher. In combination with analyses of more than 16 yr of Fermi-LAT data covering 0.1 GeV–1 TeV, we find that the spectrum above 30 GeV deviates significantly from a single power law and is best described by a smoothly broken power law with a spectral index of 1.90 ± 0.15stat (3.41 ± 0.19stat) below (above) a break energy of 0.63 ± 0.21stat TeV. Given differences in the angular resolution of LHAASO-WCDA and IACTs, TeV γ-ray emission detected with LHAASO may have a significant contribution from regions surrounding the SNR illuminated by particles accelerated earlier, which, however, are treated as background by IACTs. Detailed modeling can be used to constrain the acceleration processes of TeV particles in the early stage of SNR evolution.

Keywords: Supernova remnants, Gamma-ray astronomy, High energy astrophysics
Eccentricities of Close Stellar Binaries. Orbits of stellar binaries are in general eccentric. These eccentricities encode information about their early lives. Here, we use thousands of main-sequence binaries from the Gaia DR3 catalog to reveal that binaries inward of a few astronomical units exhibit a simple Rayleigh distribution with a mode of σe ≃ 0.3. We find the same distribution for binaries from M to A spectral types, and from tens of days to thousands of days (possibly extending to tens of astronomical units). This observed distribution is most likely primordial and its invariance suggests a single universal process. One possibility is eccentricity excitation by circumbinary disks. Another, as is suggested by the Rayleigh form, is weak scattering and ejection of brown-dwarf objects. We explore this latter scenario and find that the binary eccentricities reach an equipartition value of  . So to explain the observed mode, the brown dwarfs will have to be of order one-tenth the stellar masses, and be at least as abundant in the Galaxy as in the close binaries. The veracity of both proposals remains to be tested.

Keywords: Stellar populations
The Miscibility of Hydrogen and Water in Planetary Atmospheres and Interiors. Many planets in the solar system and across the Galaxy have hydrogen-rich atmospheres overlying more heavy element-rich interiors with which they interact for billions of years. Atmosphere–interior interactions are thus crucial to understanding the formation and evolution of these bodies. However, this understanding is still lacking in part because the relevant pressure–temperature conditions are extreme. We conduct molecular dynamics simulations based on density functional theory to investigate how hydrogen and water interact over a wide range of pressure and temperature, encompassing the interiors of Neptune-sized and smaller planets. We determine the critical curve at which a single homogeneous phase exsolves into two separate hydrogen-rich and water-rich phases, finding good agreement with existing experimental data. We find that the temperature along the critical curve increases with increasing pressure and shows the influence of a change in fluid structure from molecular to atomic near 30 GPa and 3000 K, which may impact magnetic field generation. The internal temperatures of many exoplanets, including TOI-270 d and K2-18 b, may lie entirely above the critical curve: the envelope is expected to consist of a single homogeneous hydrogen–water fluid, which is much less susceptible to atmospheric loss as compared with a pure hydrogen envelope. As planets cool, they cross the critical curve, leading to rainout of water-rich fluid and an increase in internal luminosity. Compositions of the resulting outer, hydrogen-rich and inner, water-rich envelopes depend on age and instellation and are governed by thermodynamics. Rainout of water may be occurring in Uranus and Neptune at present.

Keywords: Neptune, Ocean planets, Exoplanets, Quantum-chemical calculations, Mini Neptunes, Interdisciplinary astronomy, Habitable planets, Exoplanet atmospheres, Uranus
FAST Discovery of a Gas-rich and Ultrafaint Dwarf Galaxy: KK153. Based on a high-sensitivity H I survey using the Five-hundred-meter Aperture Spherical radio Telescope, we identified an isolated H I cloud with a system velocity of ∼127.0 km s‑1, which is associated with an optical galaxy KK153 in space. The H I gas of KK153 shows a typical disk-galaxy structure. Using the baryonic Tully–Fisher relation, we obtained that the distance to KK153 is 2.0  Mpc. Adopting this distance, we derived a stellar mass of 4.1 M⊙ and a neutral gas fraction of 0.63, implying that KK153 is a gas-rich ultrafaint dwarf galaxy in the Local Group or its outskirts. KK153 shows a cool (∼200 K) and warm (∼7400 K) two-phase neutral medium. The g ‑ r color distribution of KK153 suggests that new stars are mostly forming in its inner disk. The dynamical mass of KK153 is 6.9 M⊙, which is about 60 times larger than its baryonic matter. Detection of such a low-mass and gas-rich halo poses a challenge to the theory of cosmic reionization.

Keywords: Galaxy formation, Dwarf galaxies, Galaxy evolution
A Recent Supermassive Black Hole Binary in the Galactic Center Unveiled by the Hypervelocity Stars. When a binary of early-type stars from the young stellar populations in the Galactic center (GC) region is scattered to the vicinity of the supermassive black hole (SMBH) Sgr A*, one of the components would be tidally ejected as an early-type hypervelocity star (HVS) and the counterpart would be captured on a tight orbit around Sgr A*. Dozens of B-type HVSs moving faster than the Galactic escape speed have been discovered in the Galactic halo and are produced most likely by the SMBH Sgr A*. However, the velocity distribution and in particular the deficit of the HVSs above 700 km s‑1 is seriously inconsistent with the expectations of the present models. Here we show that the high-velocity deficit is due to the deficiency in close interactions of stars with the SMBH Sgr A*, because an orbiting intermediate-mass black hole (IMBH) of about 15,000 Solar mass kicked away slowly approaching stars 50–250 million years ago. The SMBH–IMBH binary formed probably after the merger of the Milky Way with the Gaia-Sausage-Enceladus dwarf galaxy, and coalesced about 10 million years ago, leading to a gravitational recoil of Sgr A* at a velocity of 0.3–0.5 km s‑1 and to a change of the HVS ejection scenarios. The SMBH–IMBH binary scenario predicts the formation of the S-star cluster at the GC with the distribution of the orbital size and stellar ages that are well consistent with the observations.

Keywords: Supermassive black holes, Galactic center, Binary stars, Hypervelocity stars, Galaxy mergers
MIRI-LRS Spectrum of a Cold Exoplanet around a White Dwarf: Water, Ammonia, and Methane Measurements. The study of the atmosphere of exoplanets orbiting white dwarfs is a largely unexplored field. With WD 0806-661 b, we present the first deep dive into the atmospheric physics and chemistry of a cold exoplanet around a white dwarf. We observed WD 0806-661 b using JWST's Mid-InfraRed Instrument Low-Resolution Spectrometer, covering the wavelength range from 5 to 12 μm, and the Imager, providing us with 12.8, 15, 18, and 21 μm photometric measurements. We carried the data reduction of those data sets, tackling second-order effects to ensure a reliable retrieval analysis. Using the TAUREX retrieval code, we inferred the pressure–temperature structure, atmospheric chemistry, mass, and radius of the planet. The spectrum of WD 0806-661 b is shaped by molecular absorption of water, ammonia, and methane, consistent with a cold Jupiter atmosphere, allowing us to retrieve their abundances. From the mixing ratio of water, ammonia, and methane we derive C/O = 0.34 ± 0.06,  , and N/O = 0.023 ± 0.004 and the ratio of detected metals as a proxy for metallicity. We also derive upper limits for the abundance of CO and CO2 (1.2 × 10‑6 and 1.6 × 10‑7, respectively), which were not detected by our retrieval models. While our interpretation of WD 0806-661 b's atmosphere is mostly consistent with our theoretical understanding, some results—such as the lack of evidence for water clouds, an apparent increase in the mixing ratio of ammonia at low pressure, or the retrieved mass at odds with the supposed age—remain surprising and require follow-up observational and theoretical studies to be confirmed.

Keywords: Bayesian statistics, James Webb Space Telescope, Direct imaging, Spectroscopy, Exoplanet atmospheres
A JWST Panchromatic Thermal Emission Spectrum of the Warm Neptune Archetype GJ 436b. GJ 436b is the archetype warm Neptune exoplanet. The planet's thermal emission spectrum was previously observed via intensive secondary eclipse campaigns with Spitzer. The atmosphere has long been interpreted to be extremely metal-rich, out of chemical equilibrium, and potentially tidally heated. We present the first panchromatic emission spectrum of GJ 436b observed with JWST's NIRCAM (F322W2 and F444W) and MIRI (LRS) instruments between 2.4 and 11.9 μm. Surprisingly, the JWST spectrum appears significantly fainter around 3.6 μm than that implied by Spitzer photometry. The molecular absorption features in the spectrum are relatively weak, and we only find tentative evidence of CO2 absorption at 2σ. Under the assumption of a dayside blackbody, we find Tday = 662.8 ± 5.0 K, which is similar to the zero Bond albedo equilibrium temperature. We use it to obtain a 3σ upper limit on the Bond albedo of AB ≤ 0.66. To understand the spectrum, we employ 1D radiative–convective models but find that atmospheric constraints depend strongly on model assumptions. If thermochemical equilibrium is assumed, we find a cloudy metal-enriched atmosphere (metallicity ≥300× solar). We employ 1D photochemical modeling to show that the observed spectrum is also consistent with a cloud-free, relatively lower metallicity atmosphere (metallicity ≥80× solar) with a cold internal temperature (Tint ∼ 60 K). These are much lower metallicities and internal temperatures than inferences from Spitzer photometry. The low Tday and nondetection of transmission features at high spectral resolution do suggest a role for cloud opacity, but this is not definitive.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres, Exoplanets
Cross Helicity and the Helium Abundance as an In Situ Metric of Solar Wind Acceleration. The two-state solar wind paradigm is based on observations showing that slow and fast solar wind have distinct properties like helium abundances, kinetic signatures, elemental composition, and charge-state ratios. Nominally, the fast wind originates from solar sources that are continuously magnetically open to the heliosphere like coronal holes while the slow wind is from solar sources that are only intermittently open to the heliosphere like helmet streamers and pseudostreamers. The Alfvénic slow wind is an emerging third class of solar wind that challenges the two-state fast/slow paradigm. It has slow wind speeds but is highly Alfvénic, i.e., has a high correlation between velocity and magnetic field fluctuations along with low compressibility typical of Alfvén waves, which is typically observed in fast wind. Its other properties are also more similar to the fast than slow wind. From 28 yr of Wind observations at 1 au, we derive the solar wind helium abundance (AHe), Alfvénicity (∣σc∣), and solar wind speed (vsw). Characterizing vsw as a function of ∣σc∣ and AHe, we show that the maximum solar wind speed for plasma accelerated in source regions that are intermittently open is faster than the minimum solar wind speed for plasma accelerated in continuously open regions. We infer that the Alfvénic slow wind is likely solar wind originating from open field regions with speeds below the maximum solar wind speed for plasma from intermittently open regions. We then discuss possible implications for solar wind acceleration. Finally, we utilize the combination of helium abundance and normalized cross helicity to present a novel solar wind categorization scheme that illustrates the transition in observations of solar wind at 1 au from magnetically closed to magnetically open sources.

Keywords: Slow solar wind, Magnetohydrodynamics, Abundance ratios, Fast solar wind, Solar wind, Chemical abundances, Alfven waves
Streams, Shells, and Substructures in the Accretion-built Stellar Halo of NGC 300. We present deep optical observations of the stellar halo of NGC 300, an LMC-mass galaxy, acquired with the DEEP subcomponent of the DECam Local Volume Exploration survey using the 4 m Blanco Telescope. Our resolved star analysis reveals a large, low surface brightness stellar stream (MV ∼ ‑8.5; [Fe/H] = ‑1.4 ± 0.15) extending more than 40 kpc north from the galaxy's center. We also find other halo structures, including potentially an additional stream wrap to the south, which may be associated with the main stream. The morphology and derived low metallicities of the streams and shells discovered surrounding NGC 300 are highly suggestive of a past accretion event. Assuming a single progenitor, the accreted system is approximately Fornax-like in luminosity, with an inferred mass ratio to NGC 300 of approximately 1:15. We also present the discovery of a metal-poor globular cluster (GC) (Rproj = 23.3 kpc; MV = ‑8.99 ± 0.16; [Fe/H] ≈ ‑1.6 ± 0.6) in the halo of NGC 300, the furthest identified GC associated with NGC 300. The stellar structures around NGC 300 represent the richest features observed in a Magellanic Cloud analog to date, strongly supporting the idea that accretion and subsequent disruption is an important mechanism in the assembly of dwarf galaxy stellar halos.

Keywords: Accretion, Stellar streams, Dwarf galaxies, Galaxy stellar halos, Galaxy evolution