Sazuna/UAT_keywords huggingface dataset:
High Significance Detection of the Dark Substructure in Gravitational Lens SDSS J0946+1006 by Image Pixel Supersampling. Recent studies have shown that the dark substructure reported in the gravitational lens SDSS J0946+1006 has a high central density, which is in apparent tension with the flat cold dark matter (ΛCDM) paradigm. However, its detection significance has been found in D. J. Ballard et al. to be sensitive to prior assumptions about the smoothness of the source galaxy. Here we show that the detection significance of the substructure is higher than previously reported (log-Bayes factor  , equivalent to a ∼17σ detection) by approximating the integration of light over each pixel via ray tracing and averaging over many subpixels—a technique known as supersampling—and this result is insensitive to the assumed prior on the source galaxy smoothness. Assuming a dark matter subhalo, the combination of supersampling and modeling both sets of lensed arcs also tightens the subhalo constraints: we find the subhalo's projected mass within 1 kpc lies in the range (2.2–3.4) × 109M⊙ at 95% confidence in our highest evidence model, while the log-slope of the subhalo's projected density at 1 kpc is steeper than ‑1.75 at the 95% confidence level, further establishing it as an outlier compared to expectations from CDM. We also identify a systematic that has biased the slope of the primary lensing galaxy's density profile in prior studies, which we speculate might be due to the presence of dust or an imperfect foreground subtraction. Our analysis places the existence of the substructure on firmer ground, and should motivate deeper follow-up observations to better constrain its properties and clarify its apparent tension with ΛCDM.

Keywords: Strong gravitational lensing, Dwarf galaxies, Dark matter
Climate Transition to Temperate Nightside at High Atmosphere Mass. Our recent work shows how M-Earth climates and transmission spectra depend on the amount of ice-free ocean on the planet's dayside and the mass of N2 in its atmosphere. M-Earths with more ice-free ocean and thicker atmospheres are hotter and more humid and have larger water vapor features in their transmission spectra. In this paper, we describe a climate transition in high-pN2 simulations from the traditional "eyeball" M-Earth climate, in which only the substellar region is temperate, to a "temperate nightside" regime, in which both the dayside and the nightside are entirely ice-free. Between these two states, there is a "transition" regime with partial nightside ice cover. We use 3D climate simulations to describe the climate transition from frozen to deglaciated nightsides. We attribute this transition to increased advection and heat transport by water vapor in thicker atmospheres. We find that the nightside transitions smoothly back and forth between frozen and ice-free when the instellation or pCO2 is perturbed, with no hysteresis. We also find an analogous transition in colder planets: those with thin atmospheres can have a dayside hot spot when the instellation is low, whereas those with more massive atmospheres are more likely to be in the "snowball" regime, featuring a completely frozen dayside, due to the increased advection of heat away from the substellar point. We show how both of these climate transitions are sensitive to instellation, land cover, and atmosphere mass. We generate synthetic transmission spectra and phase curves for the range of climates in our simulations.

Keywords: Habitable planets, Exoplanet atmospheres, Exoplanet surface composition
The Influence of Chromospheric Activity on Line Formation. One of the primary sources of stellar spectral variability is magnetic activity. While our current understanding of chromospheric activity is largely derived from specific lines sensitive to chromospheric heating, such as the Ca II H and K doublet, previous observational studies have shown that other spectral lines are also affected. To investigate the influence of activity on line formation in greater detail, we constructed a set of stellar models for hypothetical G2 dwarf stars with varying levels of activity and calculated their synthetic spectra. A comparison of these spectra revealed two spectral regions most significantly impacted by activity: approximately 3300–4400 Å and 5250–5500 Å. By calculating the total contribution function of the lines, we determined that the emergence of a secondary chromospheric contribution to line formation is the primary mechanism driving these changes. Based on our calculations and analysis, we compiled a list of transition lines and their corresponding changes due to chromospheric activity. This list could serve as a valuable tool for selecting spectral lines applicable to a wide range of astrophysical studies.

Keywords: Stellar chromospheres, Late-type dwarf stars, Stellar activity
Automatic Machine Learning Framework to Study Morphological Parameters of AGN Host Galaxies within z &lt; 1.4 in the Hyper Supreme-Cam Wide Survey. We present a composite machine learning framework to estimate posterior probability distributions of bulge-to-total light ratio, half-light radius, and flux for active galactic nucleus (AGN) host galaxies within z &lt; 1.4 and m &lt; 23 in the Hyper Supreme-Cam (HSC) Wide survey. We divide the data into five redshift bins: low (0 &lt; z &lt; 0.25), mid (0.25 &lt; z &lt; 0.5), high (0.5 &lt; z &lt; 0.9), extra (0.9 &lt; z &lt; 1.1), and extreme (1.1 &lt; z &lt; 1.4), and train our models independently in each bin. We use PSFGAN to decompose the AGN point-source light from its host galaxy, and invoke the Galaxy Morphology Posterior Estimation Network (GaMPEN) to estimate morphological parameters of the recovered host galaxy. We first trained our models on simulated data, and then fine-tuned our algorithm via transfer learning using labeled real data. To create training labels for transfer learning, we used GALFIT to fit ∼20,000 real HSC galaxies in each redshift bin. We comprehensively examined that the predicted values from our final models agree well with the GALFIT values for the vast majority of cases. Our PSFGAN + GaMPEN framework runs at least three orders of magnitude faster than traditional light-profile fitting methods, and can be easily retrained for other morphological parameters or on other data sets with diverse ranges of resolutions, seeing conditions, and signal-to-noise ratios, making it an ideal tool for analyzing AGN host galaxies from large surveys coming soon from the Rubin-LSST, Euclid, and Roman telescopes.

Keywords: AGN host galaxies, Neural networks, Convolutional neural networks, Astronomy data analysis, Galaxy classification systems, Active galactic nuclei, Extragalactic astronomy, Galaxies
Torsional Alfvén Shock Waves in Stratified Coronal Loops. The evolution of weakly nonlinear Alfvén waves in coronal loops in the density structuring both across and along the field while experiencing dissipation is highlighted. Energy transfer due to shock formation in coronal loops provides the basis for the context of the present study. Coronal loops are modeled analytically using the magnetohydrodynamic (MHD) theory in cylindrical geometry, incorporating stratification and viscosity. The effects of the external medium, along with equilibrium conditions, are considered, with the background magnetic field aligned parallel to the loop axis. The second-order thin flux tube approximation is employed to derive a Cohen–Kulsrud–Burgers type of evolutionary equation that highlights the influences of nonlinear, dissipative, and stratification terms, alongside the effect of the external medium. The Alfvén wave speed in coronal loops reaches its maximum when shocks are experienced. If not due to low amplitudes, the maximum is observed at the other footpoint. The location of shock formation is determined by the ratio of the Alfvén wave amplitude and the background Alfvén wave speed. The existence of energy transfer mechanisms due to MHD shocks at various locations of coronal loops, especially loop footpoints, brings to mind that observed energy transfers in the case of coronal loops or a set of loops not only provide coronal heating but also provide transition region heating subject to conditions. For high plasma-β values at lower altitudes, shock formation is less dependent on the external medium and depends strongly on the loop's internal dynamics. This is contrary to open magnetic structures.

Keywords: Solar coronal loops, Magnetohydrodynamics, Alfven waves, Solar corona
Multiband Nonthermal Radiative Properties of the Pulsar Wind Nebula CTB 87. The pulsar wind nebula CTB 87 (G74.9+1.2) is one of the sources emitting γ-rays with energies higher than 10 TeV, as measured by the Very Energetic Radiation Imaging Telescope Array System telescope. In this study, we undertake a reanalysis of the GeV emission from the CTB 87 region, utilizing ∼16 yr of high-energy γ-ray data collected with the Fermi Large Area Telescope. In the energy range of 0.03–1 TeV, the spectrum can be adequately described by a power-law model with an index of 1.34 ± 0.18, and the integral energy flux is calculated to be (7.25 ± 1.36) × 10‑13 erg cm‑2 s‑1. Based on the multiband data, we have employed a time-dependent model to investigate the nonthermal emission properties of CTB 87. In the model, it is assumed that particles with broken power-law energy distributions are continuously injected into the nebula. This results in multiband nonthermal emission being produced by relativistic leptons via synchrotron radiation and inverse Compton processes. Furthermore, the model suggests an energy of approximately 2.4 PeV for the most energetic particle in the nebula.

Keywords: Non-thermal radiation sources, Astronomy data analysis, Pulsar wind nebulae
Radial Dependence of Ion Fluences in the 2023 July 17 Solar Energetic Particle Event from Parker Solar Probe to STEREO and ACE. In the latter moments of 2023 July 17, the solar active region (AR) 13363, near the southwestern face of the Sun, was undergoing considerable evolution, which resulted in a significant solar energetic particle (SEP) event measured by Parker Solar Probe's Integrated Science Investigation of the Sun (IS⊙IS) and near-Earth spacecraft. Remote observations from GOES and CHASE captured two M5.0+ solar flares that peaked at 23:34 and 00:06 UT from the source region. In tandem, STEREO COR2 first recorded a small, narrow coronal mass ejection (CME) emerging at 22:54 UT and then saw a major halo CME emerge at 23:43 UT with a bright, rapidly expanding core and CME-driven magnetic shock with an estimated speed of ∼1400 km s‑1. Parker Solar Probe was positioned at 0.65 au, near-perfectly on the nominal Parker spiral magnetic field line, which connected Earth and the AR for a 537 km s‑1 ambient solar wind speed at L1. This fortuitous alignment provided the opportunity to examine how the SEP velocity dispersion, energy spectra, elemental composition, and fluence varied from 0.65 to 1 au along a shared magnetic connection to the Sun. We find a strong radial gradient, which is best characterized for H and He as r‑4.0, and most surprisingly, is stronger for O and Fe, which is better described by r‑5.7.

Keywords: Solar energetic particles, Solar storm, Solar activity, Solar coronal mass ejections
Probing Cosmology with 92 Localized Fast Radio Bursts and DESI BAO. Recent baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) collaboration, combined with the cosmic microwave background (CMB) and type Ia supernovae observations, suggest a preference for dynamical dark energy (DDE) with w0 &gt; −1 and wa &lt; 0. Given the cosmological origin of fast radio bursts (FRBs), the combination of their dispersion measures (DMs) and host galaxy redshifts makes localized FRBs a valuable tool for probing cosmology. Using an updated sample of 92 localized FRBs, along with DESI BAO, PlantheonPlus, and CMB data, we constrain the dark energy (DE) equation of state (EoS) under the Chevallier─Polarski─Linder parameterization. We find that even without incorporating CMB data, DDE remains preferred with   and   at a confidence level of ∼2.5σ. A joint analysis constrains these to be   and  , showing a discrepancy with ΛCDM at a ∼3.1σ level. Furthermore, using localized FRBs alone, we estimate the Hubble constant H0 to be   and  , assuming the Galactic electron density models to be NE2001 and YMW16, respectively. Thus, accurate accounting of the Galactic DM is crucial for resolving the Hubble tension with FRBs. Future BAO measurements, next-generation CMB experiments, and more localized FRBs will further constrain the DE EoS and the cosmological parameters.

Keywords: Cosmological models, High energy astrophysics, Dark energy
Modulation of X-Ray Flux by Obscuration of Neutron Star Boundary Layer. The quasiperiodic oscillations (QPOs) observed in the X-ray variability of both black hole (BH) and neutron star (NS) systems provide a tool for probing strong gravity and dense matter equations of state. Nevertheless, the mechanism of QPO modulation in NS systems, where the amplitudes of QPOs with frequencies approaching the kHz range are very high in comparison to BH high-frequency QPOs, remains an unsolved puzzle. Relativistic ray tracing of photons emitted from the immediate vicinity of compact objects has, to date, been used to investigate various mechanisms that explain the observed weak BH QPOs. However, it has not been applied to model the NS QPO signal, which requires incorporating the NS surface and a bright boundary layer (BL) on it. Here, we explore the QPO modulation mechanisms based on the BL obscuration. Using simplified models of axisymmetric oscillations of thick accretion disks (tori), we demonstrate that the disk oscillations drive the high NS QPO amplitudes through BL obscuration, which is relevant, especially for vertical oscillations. We also demonstrate that obscuration effects enable the observability of the Keplerian frequency in the case of disks that decay due to instabilities.

Keywords: Neutron stars, X-ray binary stars, Black holes
Solar Gamma-Ray Evidence for a Distinct Population of &gt;1 MeV Flare-accelerated Electrons. Significant improvements in our understanding of nuclear γ-ray line production and instrument performance allow us to better characterize the continuum emission from electrons at energies ≳300 keV during solar flares. We represent this emission by the sum of a power-law (PL) extension of hard X-rays and a power law times an exponential function (PLexp). We fit the γ-ray spectra in 25 large flares observed over 40 yr with this continuum and the calculated spectra of all known nuclear components. The PLexp is separated spectroscopically from the other components, and its presence is required with &gt;99% confidence in 18 of the flares. Its distinct origin is suggested by significant differences between its time histories and those of the PL and nuclear components in 18 of the flares. RHESSI imaging/spectroscopy of the 2005 January 20 flare reveals that the PL and nuclear components come from the footpoints, while the PLexp component comes from the corona. While the index and flux of the anisotropic PL component are dependent on the flare's heliocentric angle, the PLexp parameters do not show comparable dependences with 99.5% confidence. The PLexp spectrum is flat at low energies and rolls over at a few megaelectronvolts (MeV). Such a shape can be produced by thin-target bremsstrahlung from electrons with a spectrum that peaks between 3 and 5 MeV and by inverse Compton scattering of soft X-rays by 10–20 MeV electrons, or by a combination of the two. These electrons can produce radiation detectable at other wavelengths.

Keywords: Solar flares
Early Grain Growth in the Young Protostellar Disk HH 212 Supported by Dust Self-scattering Modeling. Grain growth in disks around young stars plays a crucial role in the formation of planets. Early grain growth has been suggested in the HH 212 protostellar disk by previous polarization observations. To confirm it and to determine the grain size, we analyze high-resolution multiband observations of the disk obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) in bands 9 (0.4 mm), 7 (0.9 mm), 6 (1.3 mm), and 3 (3 mm), as well as with the Very Large Array (VLA) in band Ka (9 mm), and we present new VLA data in bands Q (7 mm), K (1.3 cm), and X (3 cm). We adopt a parameterized flared disk model to fit the continuum maps of the disk in these bands and derive the opacities, albedos, and opacity spectral index β of the dust in the disk, taking into account the dust scattering ignored in the previous work modeling the multiband data of this source. For the VLA bands, we only include the band Q data in our modeling to avoid free–free emission contamination. The obtained opacities, albedos, and opacity spectral index β (with a value of ∼1.2) suggest that the upper limit of maximum grain size in the disk should be ∼130 μm, consistent with that implied in the previous polarization observations in band 7, supporting the grain growth in this disk. The values of the absorption opacities further highlight the need for a new dust composition model for Class 0/I disks.

Keywords: Interstellar scattering, Interstellar dust, Protoplanetary disks, Interstellar medium
Impact of Teleparallelism on Addressing Current Tensions and Exploring the GW Cosmology. The H0 and S8 tensions highlight critical discrepancies in modern cosmology, challenging the standard Lambda cold dark matter model. The H0 tension arises from conflicting measurements between local probes and early-Universe predictions. Similarly, the S8 tension, related to the amplitude of matter clustering, exposes inconsistencies between cosmic microwave background data and weak gravitational lensing surveys. The primary goal of this work is to address these tensions by modifying the underlying geometric framework. Specifically, we test two f(T) gravity models using cosmic chronometers, baryonic acoustic oscillations, gamma-ray bursts, and Pantheon+SH0ES data sets and compare the results with gravitational-wave data for validation. Both teleparallel models demonstrate promising performance in simultaneously alleviating the H0 and S8 tensions.

Keywords: Dark energy
Prompt Gamma-Ray Burst Recognition through Waterfalls and Deep Learning. Gamma-ray bursts (GRBs) are one of the most energetic phenomena in the cosmos, whose study can probe physics extremes beyond the reach of laboratories on Earth. Our quest to unravel the origin of these events and understand their underlying physics is far from complete. Central to this pursuit is the rapid classification of GRBs to guide follow-up observations and analysis across the electromagnetic spectrum and beyond. Here, we introduce a compelling approach that can set a milestone toward a new and robust GRB prompt classification method. Leveraging self-supervised deep learning, we pioneer a previously unexplored data product to approach this task: GRB waterfalls.

Keywords: Convolutional neural networks, Gamma-ray bursts, Classification, Neural networks
A Measurement of Atmospheric Circular Polarization with POLARBEAR. At millimeter wavelengths, the atmospheric emission is circularly polarized owing to the Zeeman splitting of molecular oxygen by the Earth's magnetic field. We report a measurement of the signal in the 150 GHz band using 3 yr of observational data with the POLARBEAR project. Nonidealities of a continuously rotating half-wave plate (HWP) partially convert circularly polarized light to linearly polarized light. While POLARBEAR detectors are sensitive to linear polarization, this effect makes them sensitive to circular polarization. Although this was not the intended use, we utilized this conversion to measure circular polarization. We reconstruct the azimuthal gradient of the circular polarization signal and measure its dependency from the scanning direction and the detector bandpass. We compare the signal with a simulation based on atmospheric emission theory, the detector bandpass, and the HWP leakage spectrum model. We find the ratio of the observed azimuthal slope to the simulated slope is 0.92 ± 0.01(stat) ± 0.07(sys). This ratio corresponds to a brightness temperature of 3.8 mK at the effective band center of 121.8 GHz and bandwidth of 3.5 GHz estimated from representative detector bandpass and the spectrum of Zeeman emission. This result validates our understanding of the instrument and reinforces the feasibility of measuring the circular polarization using the imperfection of continuously rotating HWP. Continuously rotating HWP is popular in ongoing and future cosmic microwave background experiments to modulate the polarized signal. This work shows a method for signal extraction and leakage subtraction that can help measure circular polarization in such experiments.

Keywords: Cosmic microwave background radiation
Mapping the Outcomes of Stellar Evolution in the Disks of Active Galactic Nuclei. The disks of active galactic nuclei (AGNs) are expected to be populated by numerous stars, either formed in the outer regions of the disk via gravitational instability or captured from the nearby nuclear star cluster. Regardless of their formation mechanism, these stars experience altered evolutionary paths, mostly shaped by the accretion of dense disk material. In this study, through the comparison of different timescales, we chart the evolutionary outcomes of these AGN stars as a function of disk radius and across a range of supermassive black hole masses, spanning from 106 to 109M⊙, for two popular AGN disk models. We find that in the outer regions of the disk, stars evolve similarly to those in the interstellar medium, but in the inner and denser regions, accretion quickly turns low-mass stars into massive stars, and their fate depends on just how quickly they accrete. If accretion occurs at a faster rate than nuclear burning, they can reach a quasi-steady "immortal" state. If stars accrete faster than they can thermally adjust, runaway accretion occurs, potentially preventing a quasi-steady state and altering the disk structure. During the AGN lifetime, in the regions of the disk that produce massive stars, supernovae (SNe) and gamma-ray bursts (GRBs) may occur within the disk over a wide range of optical depths and ambient densities. Subsequently, in the final phase of the AGN, as the disk becomes depleted, formerly immortal stars will be unable to replenish their fuel, leading to additional SNe and GRBs.

Keywords: Massive stars, Galactic center, Active galactic nuclei, Quasars
A New Algorithm for Detecting X-Ray Shots in Cyg X-1. The short-term X-ray variability of Cyg X-1 can be interpreted as a random occurrence of mini-flares known as the shots, whose physical nature is still unclear. We propose a new algorithm for shot identification in the X-ray light curve, based on baseline detection and template fitting. Compared with previous techniques, our algorithm allows us to detect shots with lower amplitudes and shorter time separations. With NICER observations, we find that, after correction for detection sensitivity, both the shot amplitude and recurrence rate are positively scaled with the mean count rate, while the recurrence rate has a much higher dependence on the count rate. These suggest that a higher mass accretion rate will drive more and slightly larger shots. We also find that the abrupt hardening near the shot peak found in previous studies is attributed to different shot profiles in different energy bands; there is no need to involve a rapid physical process to suddenly harden the emitting spectrum.

Keywords: High mass x-ray binary stars, Stellar mass black holes