Sazuna/UAT_keywords huggingface dataset:
Variations in the Milky Way's Stellar Mass Function at [Fe/H] &lt; −1. We present the first determination of the Galactic stellar mass function (MF) for low-mass stars (0.2─0.5 M⊙) at metallicities [Fe/H] ≲ −1. A sample of ∼53,000 stars was selected as metal-poor on the basis of both their halolike orbits and their spectroscopic [Fe/H] from Gaia DR3 BP/RP (XP) spectra. These metallicity estimates for low-mass stars were enabled by calibrating Gaia XP spectra with stellar parameters from SDSS-V. For −1.5 &lt; [Fe/H] &lt; −1, we find that the MF below 0.5 M⊙ exhibits a "bottom-heavy" power-law slope of α ∼ −1.6. We tentatively find that at even lower metallicities the MF becomes very bottom-light, with a near-flat power-law slope of α ∼ 0 that implies a severe deficit of low-mass stars. This metallicity-dependent variation is insensitive to the adopted stellar evolution model. These results show that the Galactic low-mass MF is not universal, with variations in the metal-poor regime. A further calibration of XP metallicities in the regime of M &lt; 0.5 M⊙ and [Fe/H] &lt; −1.5 will be essential to verify these tentative low-metallicity trends.

Keywords: Stellar populations, Stellar mass functions, Milky Way stellar halo, Low mass stars, Gaia
Meteorite Radioisotope Ages Reveal Late Dynamical Chaos in the Solar System. The orbital elements of the solar system's ancient asteroid families are highly dispersed, recording the last dynamical chaos in its history. However, dynamics alone cannot precisely date this when this terminal chaos occurred. Instead, we can precisely date the collisions triggered by such dynamical rearrangement to constrain this event. On planets, erosion, volcanism, and crustal recycling have removed almost all trace of rocks older than 4 Ga, erasing the archive of early solar system history. In contrast, the meteorite record generated by asteroid collisions represents a separate and more complete archive of the solar system's early dynamical evolution. Here we build a record of in situ ordinary chondrite meteorite apatite U-Pb ages, sensitive to collisions that induce parent-body break-up events. We show that the U-Pb records of strongly shocked and weakly shocked meteorites are distinct. The U-Pb ages of weakly shocked meteorites record the decline of radiogenic heating in asteroidal bodies. Meanwhile, shocked meteorite ages record major collisions. All sampled ordinary chondrite bodies record collisions that occurred 4480 ± 20 Ma million years ago. No further multi-parent-body clusters of shock ages are found in this record until the very recent events that brought the meteorites to Earth. These ages constrain that the last date of major dynamical chaos to modify the orbital elements of asteroids occurred at around 4480 Ma. This date is relatively late in solar system history, possibly representing the timing of an orbital instability of the giant planets.

Keywords: Isotopic abundances, Collisional processes, Cosmochemistry, Asteroid dynamics, Meteorites
Lack of Detailed Balance at Sub-ion Scales in Turbulent Solar Wind. A notable feature of turbulence in solar wind is the presence of an additional power-law spectral domain at scales below the ion inertial length. This spectral domain has been attributed to a distinct turbulent regime involving alternative wave modes. However, this interpretation is still up for debate, as is the occurrence of dissipation at these scales. Here, we present a methodology to investigate the irreversible dynamics and the lack of detailed balance for the energy of magnetic field fluctuations at ion/sub-ion scales via the asymmetric time-correlation function using high-resolution magnetic field measurements from the Parker Solar Probe mission. The preliminary results are discussed in relation to irreversibility and dissipation at ion/sub-ion scales.

Keywords: Interplanetary turbulence, Space plasmas, Solar physics, High energy astrophysics
ALMA and JWST Identification of Faint Dusty Star-forming Galaxies up to z ∼ 8 and Their Connection with Other Galaxy Populations. We exploit a new sample of around 400 bright dusty galaxies from the Atacama Large Millimeter/submillimeter Array (ALMA) CHAMPS Large Program, together with the rich JWST multiband data products in the COSMOS field, to explore and validate new selection methods for identifying dusty star-forming galaxies (DSFGs). Here we present an effective empirical selection criterion based on a newly defined parameter:  I⋆≡log10(M⋆)×log10(SFR) . Incorporating the m277W − m444W color as a second parameter further improves the purity of the selection. We then apply this method to the COSMOS2025 catalog to search for fainter dusty galaxy candidates below the ALMA CHAMPS detection limit and, through a stacking technique, identify a population of high-redshift DSFG candidates with an average flux density of S1.2mm ≍ 150 μJy and a space density of ∼6 × 10−6 Mpc−3. Three of these galaxies have been spectroscopically confirmed at zspec = 7.20, 5.85, and 5.04. This faint population seems to have been missed by most of the previous submillimeter/millimeter surveys and ground- and space-based UV−near-IR observations. We then show evidence of a possible evolutionary connection between the z &gt; 10 UV-bright galaxies recently discovered by JWST, the faint dusty z ≍ 6-8 galaxies identified here, and the population of z ≍ 3─5 massive quiescent galaxies; all of them are potentially linked as progenitor−descendant populations based on their abundance, redshifts, and stellar masses. Future spectroscopic campaigns will be essential to confirm the redshifts and physical properties of these massive, faint, high-redshift DSFG candidates.

Keywords: Early universe, Millimeter astronomy, James Webb Space Telescope, Star formation, Dust continuum emission, Galaxy evolution, Submillimeter astronomy, High-redshift galaxies, Galaxies
The Strong Fe K Line and Spin of the Black Hole X-Ray Binary MAXI J1631─479. We study the transient black hole binary MAXI J1631─479 observed simultaneously by NICER and NuSTAR in its soft spectral state. Its puzzling feature is the presence of a strong and broad Fe K line, while the continuum includes a prominent disk blackbody and a very weak power-law tail. The irradiation of the disk by a power-law spectrum fitting the tail is far too weak to explain the strong line. Previous proposals included the idea that the Fe K emission is intrinsic to the disk. Here, we propose that the strong line can be explained by the irradiation of the disk by photons from Comptonization of the disk blackbody by coronal electrons. One crucial effect is that the shape of the irradiating spectrum at ≲10 keV reflects that of the disk blackbody; it is strongly curved and has a higher flux than what would be produced by a fit with a power-law irradiation. The other effect is a relativistic enhancement of the backscattered coronal flux incident on the disk. Both effects together can account for the line, although the latter is modeled only quantitatively. While this result is independent of the physical model used for disk emission, the fitted spin depends heavily on that model. When employing a Kerr disk model for a thin disk with color correction, the fitted spin appears retrograde, rare for a Roche-lobe overflow binary. A model that accounts for both the finite thickness of the disk and radiative transfer yields a spin of a* ≍ 0.8─0.9.

Keywords: Accretion, X-ray binary stars, Rotating black holes, X-ray sources, Astrophysical black holes
A Super-Eddington, Lensing-magnified Quasar at z = 5.07 Observed with JWST. We present JWST/NIRCam F070W and F480M imaging for a quasar at z = 5.07, J0025─0145, which is magnified by a foreground lensing galaxy. Existing Hubble Space Telescope (HST) imaging does not have sufficient spatial resolution to determine whether the background quasar is multiply imaged. Exploiting the sharp point-spread function (PSF) of the F070W band, we confirm that the background quasar can be well described by a single PSF, essentially ruling out the existence of multiple lensed images. We do not detect the quasar host galaxy in either the F070W or the F480M band. Using the HST and JWST photometry, we fit the spectral energy distribution of the foreground galaxy. The estimated mass ( log(M*/M⊙)=11.15±0.16 ) and redshift ( zphot=3.62−0.04+0.06 ) of the foreground galaxy are consistent with a single-image lensing model. We estimate the maximum possible magnification of the quasar to be μmax = 3.2, which implies that the intrinsic Eddington ratio of the quasar is at least  λEddintrinsic&gt;4.9 . Therefore, J0025─0145 has one of the highest Eddington ratios among z &gt; 5 supermassive black holes known so far, suggesting the viability of super-Eddington growth for supermassive black holes in the early Universe.

Keywords: Quasars
Reanalysis of the Eclipses of LHS 1140 c: No Evidence of an Atmosphere and Implications for the Internal Structure of the Planet. We present a reanalysis of three 15 μm JWST/MIRI secondary eclipses of LHS 1140 c, a warm super-Earth (Rp = 1.272 R⊕) in a 3.78 day orbit around an M4.5 dwarf. We present a novel method for data reduction that leverages spatial derivatives of the point-spread function and compare it to widely used aperture photometry. Both methods yield an eclipse depth consistent within 1σ of the values reported in the literature. We measure an eclipse depth of 271 −30+31  ppm corresponding to a brightness temperature of  TB=595−34+33  K, consistent with a bare rock. The secondary eclipse occurs 4.1 ± 0.8 minutes before the circular-orbit-predicted time. We explore the implications of our results on the internal structure of LHS 1140 c, the orbital architecture of the system, and the possibility of future observations with JWST. We find a core-mass fraction (CMF) informed by the stellar abundances of refractory elements of 0.34 ± 0.11, inflated compared to the CMF from radius and mass measurements, suggesting the possible presence of bulk volatiles in the interior.

Keywords: Extrasolar rocky planets, Exoplanets, Astronomy data analysis, Exoplanet astronomy, Exoplanet atmospheres
Pulsations Change the Structures of Massive Stars before Explosion: Interpreting SN 2023ixf and SN 2024ggi. Massive red supergiants (RSGs) are known to become hydrodynamically unstable before they explode. Still, the vast majority of supernova (SN) models assume RSG progenitors in hydrostatic equilibrium. Here we follow the hydrodynamic evolution of RSGs with different masses and the development of radial envelope pulsations. Pulsations significantly alter the observable pre- and post-SN properties, and their importance increases substantially as a function of initial mass. We demonstrate that inferring core masses, let alone initial masses, from a single pre-SN luminosity and effective temperature of high-mass RSGs is inadvisable, as these can vary by an order of magnitude during the pulsation. We find that pulsations can naturally lead to "early-excess" emission in SN light curves and to variations in early photospheric velocities, which can help break degeneracies in Type II SNe. We compare to SN 2023ixf and SN 2024ggi, for which pulsating RSG progenitors were reported. We demonstrate that the pre- and post-SN characteristics of SN 2023ixf agree very well with our exploding pulsating RSG model and exhibit meaningful differences from hydrostatic models. The data coverage is insufficient to break all degeneracies. We find insufficient evidence for the claimed pulsation period of the SN 2024ggi progenitor, as it matches Spitzer's orbital period. This study underscores the importance of hydrodynamical pre-SN stellar models, in particular for massive stars from ≳15 M⊙. It implies an important shift in our understanding of the last stages of massive star evolution, the interpretation of pre-SN properties, the connection between SNe and their progenitors, and the missing RSG problem.

Keywords: Hydrodynamics, Stellar pulsations, Red supergiant stars, Core-collapse supernovae, Type II supernovae, Supernovae, Stellar evolution
Sound-horizon-agnostic Inference of the Hubble Constant and Neutrino Masses from Baryon Acoustic Oscillations, Cosmic Microwave Background Lensing, and Galaxy Weak Lensing and Clustering. We present a sound-horizon-agnostic determination of the Hubble constant, H0, by combining DESI Data Release 2 baryon acoustic oscillations (BAO) data with the latest cosmic microwave background (CMB) lensing measurements from Planck, the Atacama Cosmology Telescope, and SPT-3G, the angular size of the CMB acoustic scale, Dark Energy Survey Year 3 (3 × 2 pt) galaxy weak lensing and clustering correlations, and the Pantheon+ supernova sample. In this analysis, The sound horizon at the drag epoch, rd, is treated as a free parameter. By combining uncalibrated comoving distances from BAO and supernovae with constraints on the matter density Ωmh2 from CMB and galaxy lensing and clustering, we break the rd─H0 degeneracy and obtain H0 = 70.0 ± 1.7 km s−1 Mpc−1 when the sum of the neutrino masses is fixed at Σmν = 0.06 eV. With an informative prior on the amplitude of primordial fluctuations, As, we find H0 = 70.03 ± 0.9 km s−1 Mpc−1. Allowing Σmν to vary, we find that the neutrino mass is weakly constrained and strongly prior dependent. Consequently, the inferred H0 is sensitive to the choice of the Σmν prior, with a uniform prior biasing results toward larger neutrino masses and higher H0, while a logarithmic prior reduces this bias significantly. Forecasts for the completed DESI BAO program, combined with Simons Observatory─like CMB lensing, next-generation 3 × 2 pt data, and expanded supernova samples predict σ(H0) ≃ 0.67 km s−1 Mpc−1 with fixed Σmν, and σ(H0) ≃ 1.1 km s−1 Mpc−1 with Σmν &lt; 0.133 eV (&lt;0.263 eV) at 68% (95%) confidence limit when Σmν is varied.

Keywords: Hubble constant, Recombination (cosmology), Cosmological neutrinos, Cosmological parameters
A Multimessenger Search for the Supermassive Black Hole Binary in 3C 66B with the Parkes Pulsar Timing Array. A subparsec supermassive black hole binary (SMBHB) at the center of the galaxy 3C 66B is a promising candidate for continuous gravitational-wave searches with pulsar timing arrays (PTAs). In this work, we search for such a signal in the third data release of the Parkes Pulsar Timing Array. Matching our priors to estimates of binary parameters from electromagnetic (EM) observations, we find a log Bayes factor  lnB=−0.0027(7) , highlighting that the source can be neither confirmed nor ruled out. We place upper limits at 95% credibility on the chirp mass  M&lt;6.90×108M⊙ , and on the characteristic strain amplitude  log10(h0)&lt;−14.44 . This partially rules out the parameter space suggested by EM observations of 3C 66B. We also independently reproduce the calculation of the chirp mass with 3 mm flux monitor data of the unresolved core of 3C 66B. Based on this, we outline a new methodology for constructing a joint likelihood of EM and gravitational-wave data from SMBHBs. Finally, we suggest that targeted searches may allow firmly established SMBHB candidates to be treated as standard sirens, for complementary constraints on the Universe's expansion rate.

Keywords: Astronomy data analysis, Gravitational waves, Pulsars
Bayesian Inference of Gravity through Realistic 3D Modeling of Wide Binary Orbits: General Algorithm and a Pilot Study with HARPS Radial Velocities. When 3D relative displacement r and velocity v between the pair in a gravitationally bound system are precisely measured, the six measured quantities at one phase can allow elliptical orbit solutions at a given gravitational parameter G. Due to degeneracies between orbital-geometric parameters and G, individual Bayesian inferences and their statistical consolidation are needed to infer G as recently suggested by a Bayesian 3D modeling algorithm. Here, I present a fully general Bayesian algorithm suitable for wide binaries with two (almost) exact sky-projected relative positions (as in the Gaia data release 3) and the other four sufficiently precise quantities. Wide binaries meeting the requirements of the general algorithm to allow for its full potential are rare at present, largely because the measurement uncertainty of the line-of-sight (radial) separation is usually larger than the true separation. As a pilot study, the algorithm is applied to 32 Gaia binaries for which precise HARPS radial velocities are available. The value of  Γ≡log10G/GN  (where GN is Newton's constant) is  −0.002−0.018+0.012  supporting Newton for a combination of 24 binaries with Newtonian acceleration gN &gt; 10−9m s−2, while it is  Γ=0.134−0.036+0.056  ( 0.143−0.041+0.068 ) for 8 (6) binaries with gN &lt; 10−9 (&lt;10−9.5) m s−2 representing ≳3.5σ discrepancy with Newton. However, one system (stars HD 189739 and HD 189760) dominates the signal. Without it, the tension with Newton is significantly lessened with  Γ=0.063−0.041+0.065 . Thus, to verify the tentative signal, many such systems need to be discovered, and their kinematic nature such as any possibility of hidden tertiary stars needs to be thoroughly addressed. The pilot study demonstrates the potential of the algorithm in measuring and testing gravity at low acceleration with future samples of wide binaries.

Keywords: Binary stars, Gravitation, Non-standard theories of gravity, Wide binary stars, Modified Newtonian dynamics
Joint Observation of SGR J1935+2154 with Insight-HXMT and KM40m during the Active Episode of 2022 October. SGR J1935+2154 is the so-far unique magnetar from which fast radio bursts (FRBs) have been detected. In 2022 October, it resumed its burst activity, and we implemented a dedicated target-of-opportunity observation on it from 2022 October 13 to November 1 (about 940 ks in total) with Insight-HXMT, while the KM40m radio telescope has observed this source for about 1400 hr since October 15. We searched the data of Low Energy (LE), Medium Energy (ME), and High Energy (HE) X-ray telescopes onboard Insight-HXMT in the overlapping observation time windows with the KM40m radio telescope and revealed 60 magnetar X-ray bursts (MXBs), while KM40m only detected 1 radio burst. In particular, we find that there is an X-ray burst on October 21 (denoted as MXB 221021) temporally associated with this radio burst. Interestingly, this association event shows very different morphology from the X-ray and radio association events from this source reported before (e.g., MXB/FRB 200428). Moreover, we systematically analyzed the temporal and spectral properties of the sample of MXBs during this observation and found that the (radio-associated) MXB 221021 shows some different properties from other MXBs without associated radio bursts. These findings shed new light on the physical mechanisms of X-ray bursts and radio burst emission in magnetars.

Keywords: Magnetars, Soft gamma-ray repeaters
JWST/MIRI-MRS View of the Metal-poor Galaxy CGCG 007-025: The Spatial Location of Polycyclic Aromatic Hydrocarbons and Very Highly Ionized Gas. Polycyclic aromatic hydrocarbons (PAHs) are key diagnostics of the physical conditions in the interstellar medium and are widely used to trace star formation in the mid-infrared (mid-IR). The relative strengths of mid-IR PAH features (e.g., 6.2, 7.7, and 11.3 μm) are sensitive to both the size and ionization state of the molecules and can be strongly influenced by the local radiation field. However, at low metallicities (Z &lt; 0.2Z⊙), detecting PAHs remains notoriously difficult, likely reflecting a combination of suppressed formation and enhanced destruction mechanisms. We present new JWST/MIRI Medium Resolution Spectroscopy (MRS) observations of the metal-poor (Z ∼ 0.1Z⊙) dwarf galaxy CGCG 007-025. We confirm the tentative PAH detection previously reported from Spitzer data and, for the first time, identify a compact (∼50 pc) PAH-emitting region nearly cospatial with the newly detected [Ne V] (Ionization potential (I.P.) ∼ 97 eV) emission and the galaxy's most metal-poor, strongly star-forming region. The PAH11.3μm and PAH 12.7μm features are detected, while no emission is found from other typically brighter features, suggesting a PAH population dominated by large, neutral molecules resilient to hard ionizing fields. When compared with models, mid-IR line ratios involving [Ne III], [O IV], and [Ne V] can only be reproduced by a combination of star formation and AGN ionization, with the latter contributing 4%─8%. The [O IV] and [Ne V] luminosities exceed what massive stars or shocks can produce, highlighting a puzzling scenario in line with recent JWST observations of similar galaxies. This work provides a crucial reference for studying the physical conditions of the dust and star formation in low-metallicity starburst regions, environments typical of the early Universe.

Keywords: Blue compact dwarf galaxies, Polycyclic aromatic hydrocarbons, Infrared spectroscopy, Emission line galaxies, Interstellar medium
First Detailed MeerKAT Imaging Spectroscopy of a Solar Flare. Radio observations provide powerful diagnostics of energy release, particle acceleration, and transport processes in solar flares. However, despite recent progress in radio interferometric imaging spectroscopy, current instruments still face limitations in image fidelity and resolution, restricting detailed spectroscopic studies of flaring regions. Here we present high-fidelity imaging spectroscopy of an M1.3 GOES class flare with MeerKAT, a precursor to the future-generation array SKA-Mid. Radio emissions at the observed frequencies typically originate in the low corona, offering valuable insights into magnetic reconnection and primary energy-release sites. The obtained images achieve an unprecedented dynamic range exceeding 103, enabling simultaneous analysis of bright coherent bursts and faint incoherent emission from the active region. Multiple spatially distinct coherent sources are identified, implying contributions from different populations of accelerated electrons. The incoherent emission extends beyond Atmospheric Imaging Assembly structures, highlighting MeerKAT's ability to detect dilute but hot plasma invisible to extreme-ultraviolet instruments. Combined with cotemporal hard X-ray images and magnetic field extrapolations, the radio sources are located within distinct magnetic structures, further revealing their association with different populations of accelerated electrons. These results demonstrate MeerKAT imaging spectroscopy as a powerful diagnostic of solar flares and pave the way for future solar flare studies with SKA-Mid.

Keywords: Solar flares, Solar radio emission, Non-thermal radiation sources, Solar radio flares, Radio interferometry
The Role of Faraday Rotation in the Polarization of the X-Rays from Magnetically Powered Black Hole Coronas. Magnetic reconnection is one of the prime candidate mechanisms that may energize the plasma emitting the strongly polarized X-ray emission from black hole X-ray binaries (BHXRBs) in their hard states. The mechanism requires strong magnetic fields in the upstream plasma entering the reconnection layer, and weaker, but still substantial, magnetic fields in the downstream regions. In this Letter, we estimate the coronal magnetic fields for three different magnetic energy dissipation mechanisms: plasmoid-dominated magnetic reconnection, fast collisionless reconnection, and magnetic field relaxation. We show that the lack of strong Faraday depolarization constrains viable models and can be used to benchmark numerical accretion flow models. We conclude by discussing the difficulties of disentangling the various effects that can depolarize the signals from BHXRBs at low energies. We furthermore emphasize that Faraday rotation is unlikely to play a role in the polarization of the coronal X-ray emission of active galactic nuclei.

Keywords: X-ray astronomy, High energy astrophysics, Kerr black holes, Stellar mass black holes, Active galactic nuclei, Astrophysical black holes