Sazuna/UAT_keywords huggingface dataset:
A Detailed Time-resolved and Energy-resolved Spectro-polarimetric Study of Bright Gamma-Ray Bursts Detected by AstroSat CZTI in Its First Year of Operation. The radiation mechanism underlying the prompt emission remains unresolved and can be resolved using a systematic and uniform time-resolved spectro-polarimetric study. In this paper, we investigated the spectral, temporal, and polarimetric characteristics of five bright gamma-ray bursts (GRBs) using archival data from AstroSat CZTI, Swift Burst Alert Telescope, and Fermi/GBM. These bright GRBs were detected by CZTI in its first year of operation, and their average polarization characteristics have been published in Chattopadhyay et al. In the present work, we examined the time-resolved (in 100–600 keV) and energy-resolved polarization measurements of these GRBs with an improved polarimetric technique such as increasing the effective area and bandwidth (by using data from low-gain pixels), using an improved event selection logic to reduce noise in the double events and extend the spectral bandwidth. In addition, we also separately carried out detailed time-resolved spectral analyses of these GRBs using empirical and physical synchrotron models. By these improved time-resolved and energy-resolved spectral and polarimetric studies (not fully coupled spectro-polarimetric fitting), we could pin down the elusive prompt emission mechanism of these GRBs. Our spectro-polarimetric analysis reveals that GRB 160623A, GRB 160703A, and GRB 160821A have Poynting flux-dominated jets. On the other hand, GRB 160325A and GRB 160802A have baryonic-dominated jets with mild magnetization. Furthermore, we observe a rapid change in polarization angle by ∼90° within the main pulse of very bright GRB 160821A, consistent with our previous results. Our study suggests that the jet composition of GRBs may exhibit a wide range of magnetization, which can be revealed by utilizing spectro-polarimetric investigations of the bright GRBs.

Keywords: Gamma-ray bursts
Stochastic Gravitational Wave Background from Cosmological Neutrino-dominated Accretion Flows. We investigate the stochastic gravitational wave background (SGWB) from neutrino-dominated accretion flows (NDAFs) based on the results of our fallback core-collapse supernova (CCSN) simulations. We find that the predicted SGWB is mainly determined by the typical CCSN initial explosion energy and progenitor metallicity. For the optimistic cases in which the typical initial explosion energy is low, the SGWB from NDAFs without disk outflows might be detected by next-generation space-based interferometers such as DECi-hertz Interferometer Gravitational wave Observatory and Big Bang Observer. In the low-frequency regime ∼10‑3–10‑1 Hz, this background is comparable to that expected from standard inflationary models. Therefore, the SGWB from NDAFs may become a foreground for research of the SGWB generated in the inflationary epoch. Combining the diffuse NDAF neutrino background and SGWB from NDAFs, one may constrain the properties of the CCSNe and NDAFs.

Keywords: Accretion, Black holes, Core-collapse supernovae, Massive stars, Gravitational wave astronomy
Multispecies Energetic Particle Acceleration Associated with CIR and ICME-driven Shocks. A multispecies energetic particle intensity enhancement event at 1 au is analyzed. We identify this event as a corotating interaction region (CIR) structure that includes a stream interface (SI), a forward-reverse shock pair, and an embedded heliospheric current sheet (HCS). The distinct feature of this CIR event is that (1) the high-energy (&gt;1 MeV) ions show significant flux enhancement at the reverse wave (RW)/shock of the CIR structure, following their passage through the SI and HCS. The flux amplification appears to depend on the energy per nucleon. (2) Electrons in the energy range of 40.5–520 keV are accelerated immediately after passing through the SI and HCS regions, and the flux quickly reaches a peak for low-energy electrons. At the RW, only high-energy electrons (∼520 keV) show significant local flux enhancement. The CIR structure is followed by a fast-forward perpendicular shock driven by a coronal mass ejection (CME), and we observed a significant flux enhancement of low-energy protons and high-energy electrons. Specifically, the 210–330 keV proton and 180–520 keV electron fluxes are enhanced by approximately 2 orders of magnitude. This suggests that the later ICME-driven shock may accelerate particles out of the suprathermal pool. In this paper, we further present that for CIR-accelerated particles, the increase in turbulence power at SI and RWs may be an important factor for the observed flux enhancement in different species. The presence of ion-scale waves near the RW, as indicated by the spectral bump near the proton gyrofrequency, suggests that the resonant wave–particle interaction may act as an efficient energy transferrer between energetic protons and ion-scale waves.

Keywords: Solar energetic particles, Solar wind, Corotating streams
Time Series of Magnetic Field Parameters of Merged MDI and HMI Space-weather Active Region Patches as Potential Tool for Solar Flare Forecasting. Solar flare prediction studies have been recently conducted with the use of Space-Weather MDI (Michelson Doppler Imager on board Solar and Heliospheric Observatory) Active Region Patches (SMARPs) and Space-Weather HMI (Helioseismic and Magnetic Imager on board Solar Dynamics Observatory) Active Region Patches (SHARPs), which are two currently available data products containing magnetic field characteristics of solar active regions (ARs). The present work is an effort to combine them into one data product, and perform some initial statistical analyses in order to further expand their application in space-weather forecasting. The combined data are derived by filtering, rescaling, and merging the SMARP and SHARP parameters, which can then be spatially reduced to create uniform multivariate time series. The resulting combined MDI–HMI data set currently spans the period between 1996 April 4 and 2022 December 13, and may be extended to a more recent date. This provides an opportunity to correlate and compare it with other space-weather time series, such as the daily solar flare index or the statistical properties of the soft X-ray flux measured by the Geostationary Operational Environmental Satellites. Time-lagged cross correlation indicates that a relationship may exist, where some magnetic field properties of ARs lead the flare index in time. Applying the rolling-window technique makes it possible to see how this leader–follower dynamic varies with time. Preliminary results indicate that areas of high correlation generally correspond to increased flare activity during the peak solar cycle.

Keywords: Geostationary satellites, Solar flares, Astronomy databases, Space weather, Astrostatistics, Solar active regions, Solar observatories, Solar magnetic fields, Solar x-ray flares, Linear regression, Algorithms, Time series analysis
A Comprehensive Analysis of Textbook-version Afterglow Light Curves of Gamma-Ray Bursts and Implication for Universal Radiation Physics of Baryonic Jets. The standard external shock model in the thin-shell scenario predicts an onset bump in the early optical afterglow light curves of gamma-ray bursts (GRBs). We collect such a textbook-version light-curve sample of 30 GRBs and derive the jet properties from our joint fit to their X-ray and optical afterglow light curves. It is found that the distributions of the isotropic initial Lorentz factors (Γ0), the deceleration radii (R dec), and the magnetic field strength (B 0) are log-normal, but the distributions of the isotropic kinetic energy (E k,iso), medium density (n 0), and magnetization parameter (σ  B  ≡ ϵ  B /ϵ  e ) are tentatively bimodal. A tight R dec–B 0–σ  B  relation is found. It infers a universal ϵ  e  E k,iso among bursts, plausibly supporting the previous argument of a universal GRB radiation energy among GRBs. A jet break is required for modeling the light curves of 26 GRBs. The distributions of the jet opening angles and the jet-corrected kinetic energies log-normally center at  logθj,c/rad=‑1.51  (standard deviation σ = 0.27) and  log(Ek,j,c/erg)=51.78  (σ = 0.54), respectively. Those GRBs (19 GRBs), whose prompt gamma-ray emission is well estimated with broad energy-band observations, satisfy the previously discovered L  γ,p,iso–E p,z–Γ0 relation, and their gamma-ray radiation efficiencies log-normally distribute in the range from 0.04% to 10% with a central value of 0.42%. Such a low efficiency favors the baryonic fireball model, and the distribution of their baryon mass loading in the GRB ejecta log-normally centers at  log(Mfb,c/M☉)=‑5  (σ = 0.75).

Keywords: Gamma-ray bursts
Red Type-1 Quasars after Cosmic Noon and Impact on L <SUB>UV</SUB>-related Quasar Statistics. Over the past decades, nearly a million quasars have been explored to shed light on the evolution of supermassive black holes and galaxies. The ultraviolet-to-optical spectra of type-1 quasars particularly offer insights into their black hole activities. Recent findings, however, raise questions about the prevalence of red type-1 quasars of which colors might be due to dust obscuration and their potential influence on luminosity-related properties of quasars. We examine the fraction of red type-1 quasars within the redshift range of 0.68 ≤ z &lt; 2.20, applying a spectral energy distribution (SED) fitting using optical-to-mid-infrared (MIR) photometric data of Sloan Digital Sky Survey Data Release 14 quasars. Approximately 10% of the type-1 quasars exhibit red colors suggestive of dust obscuration. There is an association between the brightness of the MIR luminosity and a higher fraction of red type-1 quasars, albeit with negligible redshift evolution. By employing E(B ‑ V) values from the SED fitting, we obtained dereddened luminosity of the red type-1 quasars and reassess the quasar luminosity function (QLF) and black hole mass (M BH) estimates. Result shows a modest increase in the number density of bright quasars, linking to more flatten bright-end slope of QLFs, while M BH adjustments are minimal. Current SDSS selections with optical colors could miss a significant population of heavily dust-obscured quasars. As future MIR surveys like Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer expand, they may reveal enough obscured quasars to prompt a more profound revision of fundamental quasar properties.

Keywords: Supermassive black holes, Active galactic nuclei, Galaxy evolution, Quasars
Retrieving Young Cloudy L Dwarfs: A Nearby Planetary-mass Companion BD+60 1417B and its Isolated Red Twin W0047. We present an atmospheric retrieval analysis on a set of young, cloudy, red L dwarfs—CWISER J124332.12+600126.2 (BD+60 1417B) and WISEP J004701.06+680352.1 (W0047)—using the Brewster retrieval framework. We also present the first elemental abundance measurements of the young K-dwarf (K0) host star, BD+60 1417, using high-resolution (R = 50,000) spectra taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument on the Large Binocular Telescope. In the complex cloudy L-dwarf regime the emergence of condensate cloud species complicates retrieval analysis when only near-infrared data are available. We find that for both L dwarfs in this work, despite testing three different thermal profile parameterizations we are unable to constrain reliable abundance measurements and thus the carbon-to-oxygen ratio. While we cannot conclude what the abundances are, we can conclude that the data strongly favor a cloud model over a cloudless model. We note that the difficulty in retrieval constraints persists regardless of the signal-to-noise ratio of the data examined (S/N ∼ 10 for CWISER BD+60 1417B and 40 for WISEP W0047). The results presented in this work provide valuable lessons about retrieving young, low-surface-gravity cloudy L dwarfs. This work provides continued evidence of missing information in models and the crucial need for JWST to guide and inform retrieval analysis in this regime.

Keywords: Brown dwarfs, Substellar companion stars, Fundamental parameters of stars, Stellar abundances, L dwarfs, Atmospheric composition
Scale Separation Effects on Simulations of Plasma Turbulence. Understanding plasma turbulence requires a synthesis of experiments, observations, theory, and simulations. In the case of kinetic plasmas such as the solar wind, the lack of collisions renders the fluid closures such as viscosity meaningless and one needs to resort to higher-order fluid models or kinetic models. Typically, the computational expense in such models is managed by simulating artificial values of certain parameters such as the ratio of the Alfvén speed to the speed of light (v A/c) or the relative mass ratio of ions and electrons (m  i /m  e ). Although, typically care is taken to use values as close as possible to realistic values within the computational constraints, these artificial values could potentially introduce unphysical effects. These unphysical effects could be significant at sub-ion scales, where kinetic effects are the most important. In this paper, we use the 10-moment fluid model in the Gkeyll framework to perform controlled numerical experiments, systematically varying the ion–electron mass ratio from a small value down to the realistic proton–electron mass ratio. We show that the unphysical mass ratio has a significant effect on the kinetic range dynamics as well as the heating of both plasma species. The dissipative process for both ions and electrons becomes more compressive in nature, although the ions remain nearly incompressible in all cases. The electrons move from being dominated by incompressive viscous-like heating/dissipation to very compressive heating/dissipation dominated by compressions/rarefactions. While the heating change is significant for the electrons, a mass ratio of m  i /m  e  ∼ 250 captures the asymptotic behavior of electron heating.

Keywords: Space plasmas, Plasma physics, Interplanetary turbulence, Solar wind, Plasma astrophysics
Gaussian Process Approach for Model-independent Reconstruction of f(Q) Gravity with Direct Hubble Measurements. The increase of discrepancy in the standard procedure to choose the arbitrary functional form of the Lagrangian f(Q) motivates us to solve this issue in modified theories of gravity. In this regard, we investigate the Gaussian process, which allows us to eliminate this issue in an f(Q) model-independent way. In particular, we use the 58 Hubble measurements coming from cosmic chronometers and the radial Baryon acoustic oscillations to reconstruct H(z) and its derivatives  H'(z)  and H″(z), which leads us to reconstruct the region of f(Q), without any assumptions. The obtained mean curve along the Lambda Cold Dark Matter (ΛCDM) constant in the reconstructed region follows a quadratic behavior. This motivates us to propose a new f(Q) parameterization, i.e., f(Q) = ‑2Λ + ϵ Q 2, with the single parameter ϵ, which signifies the deviations from ΛCDM cosmology. Further, we probe the widely studied power-law and exponential f(Q) models against the reconstructed region and can improve the parameter spaces significantly compared with observational analysis. In addition, the direct Hubble measurements, along with the reconstructed f(Q) function, allow the H 0 tension to be alleviated.

Keywords: Dark energy
Modeling Compact Object Mergers GW190814 and GW200210 and Other Self-bound Compact Stars with Dark Matter Induced by Gravitational Decoupling and Its Significance to the Mass Gap. We present a rigorous study of compact objects within f(Q) gravity where electrical fields and dark matter are studied and provide novel mass–radius relations with models falling in the mass gap of the events GW190814 and GW200210. After formulating the basic equations and finding their relevant solutions, we impose the boundary conditions on the system under treatment. The decoupled solution for the strange stellar model with the dark matter density profile is obtained. The distribution patterns of the effective energy density and the radial as well as the tangential pressure and anisotropy in the system are intensively examined. The stability properties of the stellar configuration and the influence of dark matter are studied. The recent observations of supermassive compact star candidates such as PSR J1614–2230 and PSR J0952–0607 with observed masses greater than or equal to 2 M ⊙ have been employed in our study. Interestingly, the present study predicts the constraints on mass–radius measurements of the observed stars satisfying the equation of state based on the MIT bag model and employing the condition of mimicking, i.e., ρ  θ  =  χ1ρPI  in f(Q) gravity. Our graphical results exhibit that for a particular M–R curve with fixed values of the parameters, neutron stars having mass less than M max exist with larger radii within the context of the f(Q) formalism.

Keywords: Theoretical models, Dark matter, Compact objects
Probing the Spectrum of the Magnetar 4U 0142+61 with JWST. JWST observed the magnetar 4U 0142+61 with the Mid-Infrared Instrument (MIRI) and Near Infrared Camera (NIRCam) instruments within a 77 minute time interval on 2022 September 20─21. The low-resolution MIRI spectrum and NIRCam photometry show that the spectrum in the wavelength range 1.4─11 μm range can be satisfactorily described by an absorbed power-law (PL) model, f  ν  ∝ ν −α , with a spectral slope α = 0.96 ± 0.02, interstellar extinction A  V  = 3.9 ± 0.2, and normalization f 0 = 59.4 ± 0.5 μJy at λ = 8 μm. These observations do not support the passive disk model proposed in 2006 by Wang, Chakrabarty and Kaplan, based on Spitzer photometry, which was interpreted as evidence for a fallback disk from debris formed during the supernova explosion. We suggest a nonthermal origin for this emission and source variability as the most likely cause of discrepancies between the JWST data and other IR-optical observing campaigns. However, we cannot firmly exclude the presence of a large disk with a different dependence of the effective disk temperature on distance from the magnetar. Comparison with the PL fit to the hard X-ray spectrum above 10 keV, measured by the NuSTAR contemporaneously with JWST, shows that the X-ray spectrum is significantly harder. This may imply that the X-ray and IR nonthermal emission come from different sites in the magnetosphere of the magnetar.

Keywords: Neutron stars, Magnetars, Debris disks
SN 2024ggi in NGC 3621: Rising Ionization in a Nearby, Circumstellar-material-interacting Type II Supernova. We present UV─optical─near-infrared observations and modeling of supernova (SN) 2024ggi, a type II supernova (SN II) located in NGC 3621 at 7.2 Mpc. Early-time ("flash") spectroscopy of SN 2024ggi within +0.8 days of discovery shows emission lines of H I, He I, C III, and N III with a narrow core and broad, symmetric wings (i.e., "IIn-like") arising from the photoionized, optically thick, unshocked circumstellar material (CSM) that surrounded the progenitor star at shock breakout (SBO). By the next spectral epoch at +1.5 days, SN 2024ggi showed a rise in ionization as emission lines of He II, C IV, N IV/V, and O V became visible. This phenomenon is temporally consistent with a blueward shift in the UV─optical colors, both likely the result of SBO in an extended, dense CSM. The IIn-like features in SN 2024ggi persist on a timescale of t IIn = 3.8 ± 1.6 days, at which time a reduction in CSM density allows the detection of Doppler-broadened features from the fastest SN material. SN 2024ggi has peak UV─optical absolute magnitudes of M w2 = −18.7 mag and M g = −18.1 mag, respectively, that are consistent with the known population of CSM-interacting SNe II. Comparison of SN 2024ggi with a grid of radiation hydrodynamics and non─local thermodynamic equilibrium radiative-transfer simulations suggests a progenitor mass-loss rate of  Ṁ=10−2M⊙  yr−1 (v  w  = 50 km s−1), confined to a distance of r &lt; 5 × 1014 cm. Assuming a wind velocity of v  w  = 50 km s−1, the progenitor star underwent an enhanced mass-loss episode in the last ∼3 yr before explosion.

Keywords: Core-collapse supernovae, Type II supernovae, Ultraviolet astronomy, Circumstellar matter, Radiative transfer
Exploration of a Dissolving Association Made Up of IC 2602, Tucana–Horologium, and Other Young Comoving Groups. Recently Gagné et al. suggested that young moving groups with similar kinematic properties could be part of larger dissolving structures. One example was IC 2602 as the core of a group of associations, including its corona (CIC 2602), Tucana-Horologium (THA), and parts of Theia 92. We explore this hypothesis by measuring the rotation periods of 953 objects selected using Gaia DR3 kinematics from IC 2602, CIC 2602, Theia 92, and a newly identified group of stars that bridge IC 2602 and THA. We use Transiting Exoplanet Survey Satellite (TESS) full frame images to measure new rotation periods and combine these with the rotation periods for THA from Popinchalk et al. to compare their rotation period distributions and other youth indicators where available to examine if the groups could be coeval. We find strong agreement between the rotation distributions of IC 2602, CIC 2602, and THA, suggesting a shared age of ∼40 Myr, and which in combination could serve as an example of a typical distribution at this age. Theia 92 does not agree at the same level, and we explore the potential kinematic reasons it does not match the rotation period distribution of the larger groups. Additionally, in our light curve analysis we identify ∼50 potential binaries, as well as four new M dwarf complex rotators that show major morphological changes between TESS cycles. Finally, using the amplitudes of the rotation periods we measured, we find strong agreement with the amplitude–age relation presented in Morris for our 40 Myr groups.

Keywords: Moving clusters, Light curves, Young star clusters, Stellar astronomy, Stellar rotation, Star clusters
Distances to Recent Near-Earth Supernovae from Geological and Lunar <SUP>60</SUP>Fe. Near-Earth supernova blasts which engulf the solar system have left traces of their ejecta in the geological and lunar records. There is now a wealth of data on live radioactive 60Fe pointing to a supernova at 3 Myr ago, as well as the recent discovery of an event at 7 Myr ago. We use the available measurements to evaluate the distances to these events. For the better analyzed supernova at 3 Myr, samples include deep-sea sediments, ferromanganese crusts, and lunar regolith; we explore the consistency among and across these measurements, which depends sensitively on the uptake of iron in the samples as well as possible anisotropies in the 60Fe fallout. There is also significant uncertainty in the astronomical parameters needed for these calculations. We take the opportunity to perform a parameter study on the effects that the ejected 60Fe mass from a core-collapse supernova and the fraction of dust that survives the remnant have on the resulting distance. We find that with an ejected 60Fe mass of 3 × 10‑5 M ⊙ and a dust fraction of 10%, the distance range for the supernova 3 Myr ago is D ∼ 20–140 pc, with the most likely range between 50 and 65 pc. Using the same astrophysical parameters, the distance for the supernova at 7 Myr ago is D ∼ 110 pc. We close with a brief discussion of geological and astronomical measurements that can improve these results.

Keywords: Mass spectrometry, Nucleosynthesis, Nuclear abundances, Astrophysical dust processes, Supernovae