Sazuna/UAT_keywords huggingface dataset:
An Investigation into the Selection and Colors of Little Red Dots and Active Galactic Nuclei. Recently, a large number of compact sources at z &gt; 4 with blue UV slopes and extremely red rest-frame optical slopes have been found in James Webb Space Telescope (JWST) extragalactic surveys. As a subsample of these sources, commonly called "little red dots" (LRDs), have been spectroscopically observed to host a broad-line active galactic nucleus (AGN), they have been the focus of multiple recent studies in an attempt to understand the origin of their UV and optical emission. Here, we assemble a sample of 123 LRDs from the literature along with spectroscopic and photometric JWST-identified samples of AGNs to compare their colors and spectral slopes. We find that while obscured AGNs at z &lt; 6 have highly dissimilar colors to LRDs, unobscured AGNs at z &lt; 6 span a wide range of colors, with only a subsample showing colors similar to LRDs. At z &gt; 6, the majority of the unobscured AGNs that have been found in these samples are LRDs, but this may be related to the fact that these sources are at large bolometric luminosities. Because LRDs occupy a unique position in galaxy color space, they are more straightforward to target, and the large number of broad-line AGNs that do not have LRD colors and slopes are therefore underrepresented in many spectroscopic surveys because they are more difficult to preselect. Current LRD selection techniques return a large and disparate population, including many sources having 2–5 μm colors impacted by emission-line flux boosting in individual filters.

Keywords: James Webb Space Telescope, Active galactic nuclei
What Can DKIST/DL-NIRSP Tell Us about Quiet-Sun Magnetism?. Quiet-Sun regions cover most of the Sun's surface; their magnetic fields contribute significantly to solar chromospheric and coronal heating. However, characterizing the magnetic fields of the quiet Sun is challenging due to their weak polarization signal. The 4 m Daniel K. Inouye Solar Telescope (DKIST) is expected to improve our understanding of quiet-Sun magnetism. In this paper, we assess the diagnostic capability of the Diffraction Limited Near Infrared Spectropolarimeter (DL-NIRSP) instrument on DKIST for the energy transport processes in the quiet-Sun photosphere. To this end, we synthesize high-resolution, high-cadence Stokes profiles of the Fe I 630 nm lines using a realistic magnetohydrodynamic simulation, degrade them to emulate the DKIST/DL-NIRSP observations, and subsequently infer the vector magnetic and velocity fields. For the assessment, we first verify that a widely used flow tracking algorithm, the Differential Affine Velocity Estimator for Vector Magnetograms, works well for estimating the large-scale (&gt;200 km) photospheric velocity fields with these high-resolution data. We then examine how the accuracy of the inferred velocity depends on the temporal resolution. Finally, we investigate the reliability of the Poynting flux estimate and its dependence on the model assumptions. The results suggest that the unsigned Poynting flux, estimated with existing schemes, can account for about 71.4% and 52.6% of the reference ground truth at   and  . However, the net Poynting flux tends to be significantly underestimated. The error mainly arises from the underestimated contribution of the horizontal motion. We discuss the implications for DKIST observations.

Keywords: Spectropolarimetry, Solar photosphere, The Sun, Quiet sun, Solar physics, Solar magnetic fields
The PANORAMIC Survey: Pure Parallel Wide Area Legacy Imaging with JWST/NIRCam. We present the PANORAMIC survey, a pure parallel extragalactic imaging program with JWST/NIRCam observed during Cycle 1. The survey obtained ∼530 square arcmin of NIRCam imaging from 1–5 μm, totaling ∼192 hr of science integration time. This represents the largest on-sky time investment of any Cycle 1 GO extragalactic NIRCam imaging program by nearly a factor of 2. The survey includes ∼432 square arcmin of novel sky area not yet observed with JWST using at least six NIRCam broadband filters, increasing the existing area covered by similar Cycle 1 data by ∼60%. Additionally, 70 square arcmin was also covered by a seventh filter (F410M). A fraction of PANORAMIC data (∼200 square arcmin) was obtained in or around extragalactic deep fields, enhancing their legacy value. Pure parallel observing naturally creates a "wedding cake" survey with both wide and ultra-deep tiers, with 5σ point-source depths at F444W ranging from 27.8–29.4 (ABmag), and with minimized cosmic variance. The ≳6-filter strategy yields remarkably good photometric redshift performance, achieving similar median scatter and outlier fraction as CANDELS (σNMAD ∼ 0.07; η ∼ 0.2), enabling a wealth of science across redshift without need for follow-up or ancillary data. We overview the proposed survey, the data obtained as part of this program, and document the science-ready data products in the data release. PANORAMIC has delivered wide-area and deep imaging with excellent photometric performance, demonstrating that pure parallel observations with JWST are a highly efficient observing mode that is key to acquiring a complete picture of galaxy evolution from rare bright galaxies to fainter, more abundant sources across redshifts.

Keywords: AGN host galaxies, Starburst galaxies, Quenched galaxies, Extragalactic astronomy, Lyman-break galaxies, High-redshift galaxies, Redshift surveys, Galaxies
Detecting Stellar Flares in Photometric Data Using Hidden Markov Models. We present a hidden Markov model (HMM) for discovering stellar flares in light-curve data of stars. HMMs provide a framework to model time series data that are nonstationary; they allow for systems to be in different states at different times and consider the probabilities that describe the switching dynamics between states. In the context of the discovery of stellar flares, we exploit the HMM framework by allowing the light curve of a star to be in one of three states at any given time step: quiet, firing, or decaying. This three-state HMM formulation is designed to enable straightforward identification of stellar flares, their duration, and associated uncertainty. This is crucial for estimating the flare's energy, and is useful for studies of stellar flare energy distributions. We combine our HMM with a celerite model that accounts for quasiperiodic stellar oscillations. Through an injection recovery experiment, we demonstrate and evaluate the ability of our method to detect and characterize flares in stellar time series. We also show that the proposed HMM flags fainter and lower energy flares more easily than traditional sigma-clipping methods. Lastly, we visually demonstrate that simultaneously conducting detrending and flare detection can mitigate biased estimations arising in multistage modeling approaches. Thus, this method paves a new way to calculate stellar flare energy. We conclude with an example application to one star observed by TESS, showing how the HMM compares with sigma clipping when using real data.

Keywords: M dwarf stars, Astrostatistics tools, Bayesian statistics, Astrostatistics techniques, Stellar activity, Stellar flares, Low mass stars, Credible region, Time series analysis
Peculiar Dust Emission within the Orion Molecular Cloud. It is widely assumed that dust opacities in molecular clouds follow a power-law profile with an index, β. Recent studies of the Orion Molecular Cloud (OMC) 2/3 complex, however, show a flattening in the spectral energy distribution (SED) at λ &gt; 2 mm, implying nonconstant indices on scales ≳0.08 pc. The origin of this flattening is not yet known, but it may be due to the intrinsic properties of the dust grains or contamination from other sources of emission. We investigate the SED slopes in OMC 2/3 further using observations of six protostellar cores with Northern Extended Millimeter Array (NOEMA) from 2.9–3.6 mm and Atacama Large Millimeter/submillimeter Array (ALMA) Atacama Compact Array in Band 4 (1.9–2.1 mm) and Band 5 (1.6–1.8 mm) on core and envelope scales of ∼0.02–0.08 pc. We confirm flattened opacity indices between 2.9 mm and 3.6 mm for the six cores with β ≈ ‑0.16 to 1.45, which are notably lower than the β-values of &gt;1.3 measured for these sources on 0.08 pc scales from single-dish data. Four sources have consistent SED slopes between the ALMA data and the NOEMA data. We propose that these sources may have a significant fraction of emission coming from large dust grains in embedded disks, which biases the emission more at longer wavelengths. Two sources, however, had inconsistent slopes between the ALMA and NOEMA data, indicating different origins of emission. These results highlight how care is needed when combining multiscale observations or extrapolating single-band observations to other wavelengths.

Keywords: Interstellar dust, Molecular clouds, Dust continuum emission, Protostars, Radio interferometry
Unveiling Low-frequency Eclipses in Spider Millisecond Pulsars Using Wideband GMRT Observations. Eclipses of radio emission have been reported for ∼58 spider millisecond pulsars (MSPs), of which only around 19% have been extensively studied. Such studies at low frequencies are crucial for probing the properties of the eclipse medium. This study investigates eclipses in 10 MSPs in compact orbit using wide-bandwidth observations with the Giant Metrewave Radio Telescope. We report the first evidence of eclipsing for PSR J2234+0944 and J2214+3000 in one epoch, while no evidence of eclipsing was observed in the subsequent two epochs, indicating temporal evolution of the eclipse cutoff frequency in these systems. Constraints on the eclipse cutoff frequency were obtained for PSR J1555─2908, J1810+1744, and J2051─0827. Moreover, for the first time, we detected an eclipse at a nonstandard orbital phase (∼0.5) for PSR J1810+1744, with a duration longer than the eclipse observed at superior conjunction. No eclipses were detected for PSR J0751+1807, J1738+0333, and J1807─2459A at 300─500 MHz and 550─750 MHz. We calculated the mass-loss rate of the companion for PSR J1555─2908 and PSR J1810+1744 and found that these rates are insufficient to ablate the companion stars. We cataloged the  , mass function, Roche lobe filling factor, and inclination angle for compact MSP binaries with low-mass companions and found that higher spin-down flux does not guarantee eclipses. Our analysis, supported by the Kolmogorov─Smirnov statistic, confirms that eclipsing black widow binaries generally exhibit a higher mass function compared to noneclipsing black widow binaries, consistent with previous studies.

Keywords: Binary pulsars, Millisecond pulsars
Giant Hall Waves Launched by Superconducting Phase Transition in Pulsars. The cores of pulsars are expected to become superconducting soon after birth. The transition to type-II superconductivity is associated with the bunching of magnetic field lines into discrete superconducting flux tubes which possess enormous tension. The coupling of the crust to the flux tubes implies the existence of huge tangential magnetic fields at the crust–core interface. We show that the transition to superconductivity triggers a highly nonlinear response in the Hall drift of the crustal magnetic field, an effect which was neglected in previous numerical modeling. We argue that at the time of the phase transition giant Hall waves are launched from the crust–core interface toward the surface. Our models show that if the crust contains a multipolar magnetic field ∼1013 G, the amplitude of the Hall waves is ∼1015 G. The elastic deformation of the lattice is included in our models, which allows us to track the time-dependent shear stresses everywhere in the crust. The simulations indicate that the Hall waves may be strong enough to break the crust, and could cause star quakes which trigger rotation glitches and changes in the radio pulse profile. The Hall waves also couple to slow magnetospheric changes, which cause anomalous braking indices. The emission of the giant Hall waves from the crust–core interface facilitates fast flux expulsion from the superconducting core, provided that the flux tubes in the core are themselves sufficiently mobile. For all of the flux tube mobility prescriptions implemented in this work, the core approaches the Meissner state with B = 0 at late times.

Keywords: Magnetic fields, Plasma astrophysics, Neutron star cores, Radio pulsars
Redshifting the Study of Cold Brown Dwarfs and Exoplanets: The Mid-infrared Wavelength Region as an Indicator of Surface Gravity and Mass. JWST is opening many avenues for exploration. For cold brown dwarfs and exoplanets, JWST has opened the door to the mid-infrared wavelength region, where such objects emit significant energy. For the first time, astronomers have access to mid-infrared spectroscopy for objects colder than 600 K. The first spectra appear to validate the model suite known as ATMO 2020++: atmospheres that include disequilibrium chemistry and have a nonadiabatic pressure–temperature relationship. Preliminary fits to JWST spectroscopy of Y dwarfs show that the slope of the energy distribution from λ ≈ 4.5 μm to λ ≈ 10 μm is very sensitive to gravity. We explore this phenomenon using PH3-free ATMO 2020++ models and updated Wide-field Infrared Survey Explorer W2‑W3 colors. We find that an absolute 4.5 μm flux measurement constrains temperature, and the ratio of the 4.5 μm flux to the 10–15 μm flux is sensitive to gravity and less sensitive to metallicity. We identify 10 T dwarfs with red W2‑W3 colors that are likely to be very-low-gravity, young, few-Jupiter-mass objects; one of these is the previously known COCONUTS-2b. The unusual Y dwarf WISEPA J182831.08+265037.8 is blue in W2‑W3, and we find that the 4–18 μm JWST spectrum is well reproduced if the system is a pair of high-gravity 400 K dwarfs. Recently published JWST colors and luminosity-based effective temperatures for late-T and -Y dwarfs further corroborate the ATMO 2020++ models, demonstrating the potential for significant improvement in our understanding of cold, very-low-mass bodies in the solar neighborhood.

Keywords: Exoplanet astronomy, Brown dwarfs, Fundamental parameters of stars, Infrared photometry
Modeling the Magnetic Connection from Earth to Solar Corona during the May 11 Geomagnetic Superstorm. In early 2024 May, the solar active region AR 13664 released a series of X-class solar flares and multiple coronal mass ejections (CMEs) that resulted in the strongest geomagnetic storm of the last 20 yr. This study aims at improving our understanding of the magnetic connectivity between Earth and the solar corona by reconstructing the magnetic footpoint of the Earth on the solar surface during this geomagnetic superstorm. A Monte Carlo simulation was applied to model the random walk of interplanetary magnetic field lines due to low-frequency turbulence in the solar wind. This model uses local diffusion coefficients dependent on magnetic fluctuations and the correlation length of solar wind turbulence. The simulation revealed an enhanced diffusion of magnetic field lines due to the passage of CMEs, leading to a broader area of solar surface magnetically connected to Earth, particularly near AR 13664. This proximity facilitated the rapid propagation of solar energetic protons, increasing fluxes observed at L1. The findings have significant implications for predicting space weather effects on Earth and other solar system bodies, contributing to the development of more accurate models for future space exploration missions. Since the Parker spiral reconstruction is consistent with the Magnetic Connectivity Tool, validating the model's reliability, it shows promise for reconstructing magnetic connections for potential real-time purposes.

Keywords: Solar energetic particles, Interplanetary magnetic fields, Solar coronal mass ejections
Optical Quasiperiodic Oscillations with 550 Day Periodicity in the Reverberation-mapped Broad Line Quasar PG 1411+442. In this paper, optical quasiperiodic oscillations (QPOs) with 550 day periodicity related to a candidate subparsec binary black hole (BBH) system are reported in the reverberation-mapped broad line quasar PG 1411+442 but with a different line profile of broad Hα from that of broad Hβ in its rms spectrum. First, considering the sine function to describe the 18.8 yr long light curves from the Catalina Sky Survey, All-Sky Automated Survey for Supernovae, and Zwicky Transient Facility, 550 day periodicity can be confirmed with a confidence level higher than 5σ. Second, the stable 550 day optical QPOs can be reconfirmed with confidence levels higher than 5σ by the generalized Lomb–Scargle periodogram, the sine-like phase-folded light curves, and the weighted wavelet z-transform technique determined power maps. Third, based on simulated light curves by the continuous autoregressive process, a confidence level higher than 3.5σ can be confirmed for the optical QPOs not related to intrinsic active galactic nucleus (AGN) variability. Moreover, considering the spatial separation of central two black hole (BH) accreting systems with smaller than expected sizes of broad emission line regions, a central total BH mass higher than 106 M⊙ could lead to few effects of supposed BBH systems on estimated virial BH masses. Meanwhile, disk precession is not preferred due to the similar estimated sizes of the optical and near-ultraviolet emission regions, and jet precession can be ruled out due to PG 1411+442 being a radio-quiet quasar. The results strongly indicate it would be practicable, by applying very different line profiles of broad Balmer emission lines, to detect candidate BBH systems in normal broad line AGN in the near future.

Keywords: Supermassive black holes, Active galactic nuclei, Lomb-Scargle periodogram, Quasars
Physics-driven Explosions of Stripped High-mass Stars: Synthetic Light Curves and Spectra of Stripped-envelope Supernovae with Broad Light Curves. Stripped-envelope supernovae (SESNe) represent a significant fraction of core-collapse supernovae, arising from massive stars that have shed their hydrogen and, in some cases, helium envelopes. The origins and explosion mechanisms of SESNe remain a topic of active investigation. In this work, we employ radiative-transfer simulations to model the light curves and spectra of a set of explosions of single, solar-metallicity, massive Wolf–Rayet stars with ejecta masses ranging from 4 to 11 M⊙, which were computed from a turbulence-aided and neutrino-driven explosion mechanism. We analyze these synthetic observables to explore the impact of varying ejecta mass and helium content on observable features. We find that the light curve shape of these progenitors with high ejecta masses is consistent with observed SESNe with broad light curves but not the peak luminosities. The commonly used analytic formula based on rising bolometric light curves overestimates the ejecta mass of these high-initial-mass progenitor explosions by a factor of up to 2.6. In contrast, the calibrated method by Haynie et al., which relies on late-time decay tails, reduces uncertainties to an average of 20% within the calibrated ejecta mass range. Spectroscopically, the He I 1.083 μm line remains prominent even in models with as little as 0.02 M⊙ of helium. However, the strength of the optical He I lines is not directly proportional to the helium mass but instead depends on a complex interplay of factors such as the 56Ni distribution, composition, and radiation field. Thus, producing realistic helium features requires detailed radiative transfer simulations for each new hydrodynamic model.

Keywords: Core-collapse supernovae, Computational methods, Radiative transfer simulations, Supernovae, Supernova dynamics
Collision-induced Absorption Spectra of N<SUB>2</SUB> and CH<SUB>4</SUB>. Collision-induced spectra are essential for radiative transfer modeling of Titan's atmosphere. We present experimental spectra of nitrogen–methane mixtures with an accompanying fit of N2-CH4 collision-induced absorption in the 30–400 cm‑1 region at about 130 K. We found a peak absorption of 2.30 × 10‑5 cm‑1 amagat‑2 at 75 cm‑1 and a secondary peak of 1.35 × 10‑5 cm‑1 amagat‑2 at 206.5 cm‑1, which agrees with previous studies. Our work does not support the suggestion that N2-CH4 CIA in the far-infrared should be increased by about 50%, as suggested by spectroscopic modeling of Titan using data from A. Borysow &amp; C. Tang.

Keywords: Atmospheric extinction, Collision physics, Titan, Radiative transfer
Cosmic Reionization on Computers: The Evolution of the Ionizing Background and Mean Free Path. Observations of the end stages of reionization indicate that at z ≈ 5–6, the ionizing background is not uniform and the mean free path (MFP) changes drastically. As the MFP is closely related to the distribution of Lyman-limit systems (LLSs) and damped Lyα absorbers, it is important to understand them. In this study, we utilize the Cosmic Reionization on Computers (CROC) simulations, which have both sufficient spatial resolution to resolve galaxy formation and LLSs alongside a fully coupled radiative transfer, to simulate the reionization processes. We analyze two CROC boxes with distinct reionization histories and find that the distributions of the ionizing background in both simulations display significant skewness. Further, the ionizing background in the late-reionization box still displays significant fluctuations (∼40%) at z ≈ 5. We also measure the MFP along sightlines that center on potential quasar hosting halos. The evolution of the MFP measured from these sightlines exhibits a break that coincides with the disappearance of all the neutral islands in the reionization history of each box. In the absence of LLSs, the MFP will be biased high by ≈20% at z ≈ 5. We also compare the MFPs measured in random sightlines. We find that at z ≈ 5, the MFPs measured in sightlines that start from massive halos are systematically smaller by ≈10% compared with the MFPs measured in random sightlines. We attribute this difference to the concentration of dense structures within 1 pMpc of massive halos. Our findings highlight the importance of high-fidelity models in the interpretation of observational measurements.

Keywords: Reionization, Intergalactic medium
Phase-transition-induced Collapse of Proto-compact Stars and Its Implication for Supernova Explosions. A hadron–quark phase transition (PT) may trigger supernova explosions during stellar core collapse. However, both success and failure have occurred in previous attempts to explode dying stars via this mechanism. We systematically explore the outcomes of the PT-induced collapse of mock proto-compact stars (PCSs) with a constant entropy and lepton fraction, with spherically symmetric general relativistic hydrodynamic simulations and a controlled series of hybrid equations of state. Our results reveal the qualitative dependence of successful and failed explosions on the PT and quark matter characteristics. A small portion (∼0.04%‑1%) of the released binding energy ΔEB transforms into the diagnostic explosion energy Eexp,diag, which saturates at ∼6 × 1051 erg near the black hole formation. Note that our Eexp,diag represents an upper limit of the final explosion energies in realistic supernova simulations. We draw the phase diagrams indicative of the possible fates of supernova explosions driven by hadron‑quark PTs, where the control parameters are the onset density, the energy gap of the PT, and the quark matter speed of sound. Our findings can guide further self-consistent investigations on PT-driven core-collapse supernovae and help identify hadron‑quark PT-induced PCS collapse from future observations.

Keywords: Nuclear astrophysics, Supernova dynamics, Core-collapse supernovae, Compact objects