Sazuna/UAT_keywords huggingface dataset:
Dinosaur in a Haystack: X-Ray View of the Entrails of SN 2023ixf and the Radio Afterglow of Its Interaction with the Medium Spawned by the Progenitor Star (Paper I). We present the results from our extensive hard-to-soft X-ray (NuSTAR, Swift-XRT, XMM-Newton, Chandra) and meter-to-millimeter-wave radio (Giant Metrewave Radio Telescope, Very Large Array, NOEMA) monitoring campaign of the very nearby (d = 6.9 Mpc) Type II supernova (SN) 2023ixf spanning ≈4–165 days post-explosion. This unprecedented data set enables inferences on the explosion's circumstellar medium (CSM) density and geometry. In particular, we find that the luminous X-ray emission is well modeled by thermal free–free radiation from the forward shock with rapidly decreasing photoelectric absorption with time. The radio spectrum is dominated by synchrotron radiation from the same shock. Similar to the X-rays, the level of free–free absorption affecting the radio spectrum rapidly decreases with time as a consequence of the shock propagation into the dense CSM. While the X-ray and the radio modeling independently support the presence of a dense medium corresponding to an effective mass-loss rate   at R = (0.4–14) × 1015 cm (for vw = 25 km s‑1), our study points at a complex CSM density structure with asymmetries and clumps. The inferred densities are ≈10–100 times those of typical red supergiants, indicating an extreme mass-loss phase of the progenitor in the ≈200 yr preceding core collapse, which leads to the most X-ray luminous Type II SN and the one with the most delayed emergence of radio emission. These results add to the picture of the complex mass-loss history of massive stars on the verge of collapse and demonstrate the need for panchromatic campaigns to fully map their intricate environments. *The title was inspired by a news report on the rediscovery of fossilized dinosaur eggs in rural Gujarat in Indian Express 2024 October 28.

Keywords: X-ray transient sources, Core-collapse supernovae, Radio transient sources
Two Distinctly Different Characteristics of Flare-driven Coronal Rain Revealed from High-resolution Spectroscopic Imaging Observations with FISS/GST. We report on a flare-driven coronal rain event observed along postflare loops during the decay phase of an X1.6-class solar flare. Although high-resolution studies of flare-driven coronal rain have been conducted, imaging spectroscopic studies are rare due to observational difficulties. Our observation taken with the Fast Imaging Solar Spectrograph, installed at the 1.6 m Goode Solar Telescope of the Big Bear Solar Observatory, provided unprecedented high-resolution spectroscopic imaging data of coronal rain in the Hα and Ca II 854.2 nm lines. We identify two locations along postflare loops with rain displaying distinctly different thermal properties, different Doppler velocities, and different patterns of acceleration and deceleration. We also observed intense brightening at one footpoint of coronal rain, where the spectroscopic analysis reveals an energy conversion process resulting in significant localized chromospheric heating. We thoroughly investigate the footpoint brightening Doppler velocities and compare their spectral line profiles to typical flare-ribbon line profiles. We estimate the spatial scale of the fine structure of the coronal rain and the footpoint brightening. Our results provide important insights into the dynamic and thermal properties of flare-driven coronal rain and the related chromospheric response, which will help validate the flare-driven modeling of coronal rain.

Keywords: Solar active regions, Solar chromosphere, Solar flares, Solar flare spectra
Artificial Intelligence for the Characterization of the 2024 May Superstorm: Active Region Classification, Flare Forecasting, and Geomagnetic Storm Prediction. Space weather, driven by solar flares and coronal mass ejections, poses significant risks to technological systems. Accurately forecasting these events and their impact on Earth's magnetosphere remains a challenge because of the complexity of solar─terrestrial interactions. This study focuses on the solar and geomagnetic extreme events associated with the 2024 May superstorm and shows that artificial intelligence (AI) tools are able to characterize this storm at three different levels. First, using magnetogram cutouts, a vision transformer was able to classify the morphological evolution of NOAA Active Region 13644 (primarily involved in storm generation), and then a video-based deep learning method predicted the occurrence of the associated solar flares, and a data-driven method exploited in situ measurements to raise 1-hour in advance alerts of the geomagnetic storm during the entire event. These AI models outperformed traditional methods in predicting solar flare occurrences, onset, and recovery phases of the geomagnetic storm. These findings highlight the impressive potential of AI for space weather forecasting as a tool to mitigate the impact of extreme solar events on critical infrastructure.

Keywords: Solar flares, Classification, Neural networks, Space weather, Solar active regions, Solar storm
Predicting the Solar Wind Speed and Interplanetary Sector Structure during Solar Cycles 21–25. We use potential-field source-surface (PFSS) extrapolations of photospheric field data to predict the solar wind speed and interplanetary sector structure at Earth during solar cycles 21–25, and compare the results with in situ measurements. The wind speed is taken to be inversely correlated with the rate of coronal flux-tube expansion, which is derived using photospheric synoptic maps from the Wilcox Solar Observatory, the National Solar Observatory, the Global Oscillation Network Group, and the Helioseismic and Magnetic Imager. The extrapolations tend to predict too much fast wind near sunspot minimum, when the heliospheric current sheet is located near the ecliptic and the latitudinal gradients in the wind speed are very steep; the predictions are generally best during the declining phase of each cycle (with correlation coefficients of order 0.35–0.5), when large low-latitude extensions of the polar coronal holes give rise to recurrent high-speed streams. The overprediction of fast wind during 2009 and 2019 is associated with an overestimate of the areal sizes of remnant coronal holes and of the warping of the streamer belt. These in turn may be caused by an underestimate of the Sun's axial dipole or polar field strength and by the omission of the effect of the low-latitude sheet currents beyond 2.5 R⊙ on the near-coronal field. The latter currents act to decrease the sizes of open field regions relative to the PFSS model, with the result being similar to that of moving the source surface outward from 2.5 to 3.0 R⊙.

Keywords: Slow solar wind, Solar cycle, Heliosphere, Fast solar wind, Space weather, Solar wind, Interplanetary magnetic fields, Solar coronal holes
Dust Battery: A Novel Mechanism for Seed Magnetic Field Generation in the Early Universe. We propose a novel dust battery mechanism for generating seed magnetic fields in the early Universe, in which charged dust grains are radiatively accelerated, inducing strong electric currents that subsequently generate magnetic fields. Our analysis demonstrates that this process is effective even at very low metallicities (approximately ∼10−5Z⊙), and capable of producing seed fields with significant amplitudes of B ∼ μG around luminous sources over timescales of years to Myr and across spatial scales ranging from au to kpc. Crucially, we find that this mechanism is generically ∼108 times more effective than the radiatively driven electron battery or Biermann battery in relatively cool gas (≪105 K), including both neutral and ionized gas. Furthermore, our results suggest that, to first order, dissipation effects do not appear to significantly impede this process, and that it can feasibly generate coherent seed fields on macroscopically large interstellar medium (ISM) scales (much larger than turbulent dissipation scales or electron mean-free-paths in the ISM). These seed fields could then be amplified by subsequent dynamo actions to the observed magnetic fields in galaxies. Additionally, we propose a subgrid model for integration into cosmological simulations, and the required electric-field expressions for magnetohydrodynamic-particle-in-a-cell simulations that explicitly model dust dynamics. Finally, we explore the broad applicability of this mechanism across different scales and conditions, emphasizing its robustness compared to other known battery mechanisms.

Keywords: Cosmology, Galaxy formation, Magnetohydrodynamics, Plasma astrophysics, Astrophysical dust processes, Computational methods, Cosmic magnetic fields theory, Magnetic fields
Effects of Waves on the Spectral Anisotropy of the Transition Range in Solar Wind Turbulence. In the transition range of the solar wind turbulence, the magnetic spectrum has been observed to be strongly anisotropic with respect to the local mean field. However, the generation mechanism of the anisotropy remains not well understood. There are two typical types of waves existing in the transition range, including ion cyclotron waves (ICWs) and kinetic Alfvén waves (KAWs) propagating in the directions parallel and perpendicular to the magnetic field, respectively. In this work, we perform a statistical study about the effects of the waves on the spectral anisotropy of the transition range. We select 31 intervals from the measurements of Parker Solar Probe between 2018 and 2021. The magnetic helicity (σm) diagnosis is applied on the magnetic field data, and the wavelet coefficients with σm ≤ ‑0.5 and σm ≥ 0.4 are considered as signals of ICWs and KAWs, respectively. For the first time, we remove both ICWs and KAWs systematically from the power spectral density of magnetic field fluctuations and find that the magnetic spectral anisotropy in the transition range becomes significantly weaker. Specifically, the spectra in the quasi-parallel direction statistically get shallower, and the average spectral index changes from ‑5.68 ± 0.74 to ‑4.72 ± 0.56. By contrast, the spectra in the perpendicular direction get slightly steeper, and the index changes from ‑3.63 ± 0.34 to ‑3.95 ± 0.41. Moreover, the anisotropic scaling in the transition range is found to be  . The new results will help to further understand the possible mechanisms that cause the spectral anisotropy in the transition range.

Keywords: Interplanetary turbulence, Solar wind, Interplanetary magnetic fields
Radio Emission across the Entire Rotation Phases of Pulsars. Supersensitive observations of bright pulsars by the Five-hundred-meter Aperture Spherical Telescope have revealed weak radio emission continuously emerges in the rotation phases between the "main" pulse and "interpulse" of a rotating neutron star. We develop a model for the polarized radio emission radiated from different heights in the pulsar magnetosphere, and examine the emission intensity distribution over the whole rotation phases of pulsars seen from all directions by the line of sight. We find that for pulsars with small periods and a magnetosphere filled with much more relativistic particles, the polarized radio emission can be generated in all rotation phases for both the aligned and perpendicular rotating neutron stars. When the line of sight cuts the pulsar emission beam between the rotation and magnetic axes, the polarization angles have the same sense of variation gradient for the main pulse and interpulse. If the line of sight cuts the beams between the inclined magnetic axis and the equator, the opposite senses can be found for the main pulse and interpulse. In addition to the pulsed emission, we find persistent radio emission generated in the pulsar magnetosphere. The model can naturally explain the emission across the entire rotation phases.

Keywords: Radio pulsars
PKS 2131−021—Discovery of Strong Coherent Sinusoidal Variations from Radio to Optical Frequencies: Compelling Evidence for a Blazar Supermassive Black Hole Binary. Haystack and Owens Valley Radio Observatory observations recently revealed strong, intermittent, sinusoidal total flux-density variations that maintained their coherence between 1975 and 2021 in the blazar PKS 2131−021 (z = 1.283). This was interpreted as possible evidence of a supermassive black hole binary (SMBHB). Extended observations through 2023 show a coherence over 47.9 yr, with an observed period P15 GHz = (1739.8 ± 17.4) days. We reject, with p-value = 2.09 × 10−7, the hypothesis that the variations are due to random fluctuations in the red noise tail of the power spectral density. There is clearly a physical phenomenon in PKS 2131−021 producing coherent sinusoidal flux-density variations. We find the coherent sinusoidal intensity variations extend from below 2.7 GHz to optical frequencies, from which we derive an observed period Poptical = (1764 ± 36) days. Across this broad frequency range, there is a smoothly varying monotonic phase shift in the sinusoidal variations with frequency. Hints of periodic variations are also observed at γ-ray energies. The importance of well-vetted SMBHB candidates to searches for gravitational waves is pointed out. We estimate the fraction of blazars that are SMBHB candidates to be &gt;1 in 100. Thus, monitoring programs covering tens of thousands of blazars could discover hundreds of SMBHB candidates.

Keywords: Supermassive black holes, Relativistic jets, Active galactic nuclei, Radio jets
The Local Galactic Transient Survey Applied to an Optical Search for Directed Intelligence. We discuss our transient search for directed energy systems in local galaxies, with calculations indicating the ability of modest searches to detect optical Search for Extraterrestrial Intelligence sources in the closest galaxies. Our analysis follows P. Lubin, where a messenger civilization follows a beacon strategy we call "intelligent targeting." We plot the required laser time to achieve a signal-to-noise ratio of 10 and find the time for a blind transmission to target all stars in the Milky Way to be achievable for local galactic civilizations. As high cadence and sky coverage is the pathway to enable such a detection, we operate the Local Galactic Transient Survey (LGTS) targeting M31 (the Andromeda galaxy), the Large Magellanic Cloud, and the Small Magellanic Cloud via Las Cumbres Observatory's network of 0.4 m telescopes. We explore the ability of modest searches like the LGTS to detect directed pulses in optical and near-infrared wavelengths from extraterrestrial intelligence at these distances, and conclude that a civilization utilizing less powerful laser technology than we can construct in this century is readily detectable with the LGTS's observational capabilities. Data processing of 30,000 LGTS images spanning 5 yr is in progress with the TRansient Image Processing Pipeline.

Keywords: Search for extraterrestrial intelligence
The HST-Hyperion Survey: Grism Observations of a z ∼ 2.5 Protosupercluster. We present the first results and catalogs from the HST-Hyperion survey. This survey has collected 50 orbits of WFC3/F160W imaging and WFC3/G141 grism spectroscopy in the most overdense regions of the Hyperion protosupercluster at z ∼ 2.45, which are analyzed in conjunction with the adjacent 56 orbits of WFC3/F140W imaging and WFC3/G141 grism spectroscopy from the 3D-HST survey. Sources were identified and spectra were extracted using GRIZLI, which subsequently fit the combined grism data with object-matched photometric data from the COSMOS2020 catalog to obtain a redshift and best-fit spectral model. Each source was then visually inspected by multiple team members and quality flags were assigned. A total of 12,814 objects with mHST ≤ 25.0 were inspected, of which 5629 (44%) have reliable redshifts from the grism data and are sensitive to emission lines at a level of ∼8.8 × 10−18 erg s−1 cm−2 (1σ). A comparison with high-quality, ground-based spectroscopic redshifts yields a scatter of σNMAD = 0.0016. The resulting catalogs contain 125 confirmed members of the Hyperion structure within 2.40 &lt; z &lt; 2.53, with an additional 71 confirmed galaxies in projection within 2.35 &lt; z &lt; 2.65. The redshift, stellar population, and line flux catalogs, as well as all grism spectra, are publicly available.

Keywords: Protoclusters, Galaxy evolution
Critical Condition of Core-collapse Supernovae. I. One-dimensional Models. When the core of a massive star collapses, neutrino heating can energize the stalled accretion shock, leading to a successful supernova. The critical condition that characterizes the transition from accretion to explosion is a central topic of study and is often characterized by a critical protoneutron star (PNS) neutrino luminosity  , which depends on the post-collapse mass-accretion rate   from the progenitor. We examine the critical condition by solving the spherically symmetric time-dependent Euler equations with a general equation of state and realistic microphysics for a range of  , average neutrino energy &lt;ϵν&gt;, luminosity Lν, PNS radius R⋆, mass M⋆, and pre-shock Mach number   for a fixed neutrino optical depth from the PNS surface of 2/3. We derive   as a function of the input parameters. We show that increasing the pressure of the pre-shock flow, as parameterized by lowering  , lowers the normalization of the critical condition. We connect this finding with realistic massive progenitors and show that   can decrease by ∼5%–8% due to thermal changes during accretion of compositional interfaces onto the stalled shock. We test critical conditions that have been proposed in the literature, including the "antesonic" condition, the "force explosion condition," and the heuristic heating-advection timescale condition. We discuss how shock oscillations impact these critical conditions. Compared to other explosion conditions, we find that the antesonic ratio shows the least variation across the model space we explore. This work is preparatory for similar experiments in 2D axisymmetry and 3D.

Keywords: Hydrodynamical simulations, Core-collapse supernovae
Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY). II. Project Design, Current Status, and Examples of Initial Data Products. The He II reionization epoch is expected to take place at z ∼ 3–5. In this stage, the helium and metals in the intergalactic medium are further ionized with additional contributions from harder nonstellar sources, and some large-scale gravitationally bound systems approach virialization. The Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY) program utilizes high- and medium-resolution spectra of bright background quasars at z ≈ 3.9–5.2 to investigate Lyα, C IV, and other metal absorption lines during this epoch. Additionally, we employ narrowband imaging to search for Lyα emitters associated with C IV absorbers, alongside multiwavelength observations to identify and study particularly intriguing cases. In this paper, we present the design of the HIERACHY program, its current status, major scientific goals, and examples of initial data products from completed Magellan/MIKE, MagE spectroscopy, and MDM imaging observations. We also provide a brief outlook on future multiwavelength observations that may significantly impact the related science.

Keywords: High-redshift galaxy clusters, Quasars, Large-scale structure of the universe, Intergalactic medium, Reionization, Intracluster medium
Probing the He II Reionization ERA via Absorbing C IV Historical Yield (HIERACHY). III. The C IV Absorber Catalog and Initial Results on Cosmic Abundance Evolution at z ≈ 3–5. As part of the HIERACHY program, we collect the high signal-to-noise ratio and high-spectral resolution optical spectra of 25 quasars at z ≈ 4–5 to constrain the C IV evolution at z ≈ 3–5. In this paper, we report a catalog of 626 (1263) C IV absorption systems (components) at z ≈ 3–5 with a 50% completeness column density of log(NCIV/cm‑2) ≈ 12.3. The HIERACHY/MIKE C IV sample is one of the best C IV absorber samples optimized to study the intergalactic medium during the He II reionization epoch. Using 557 (1090) intervening absorption systems (components), we found the column density distribution function of C IV absorption systems with log(NCIV/cm‑2) ≳ 12.3 has a broken power-law shape, with the turnover column density log (Ncrit/cm‑2)=13.35‑0.19+0.20 , which is close to or smaller than the detection limit of most literature samples. We also found that both comoving path length number density dn/dX and cosmic abundance Ω for C IV absorption systems with log(NCIV/cm‑2) &gt; 13.2 show an increase (at the 2.2σ and 1.4σ levels, respectively) from redshift z ≈ 5–3, while absorption systems with log(NCIV/cm‑2) = 12.3–13.2 exhibit a constant dn/dX and ΩCIV.

Keywords: Reionization, Circumgalactic medium, Quasar absorption line spectroscopy, Intergalactic medium
Excitation of Post-asymptotic Giant Branch Star Binary Eccentricity by Massive Polar-aligned Circumbinary Disks. Many post-asymptotic giant branch star binaries are observed to have relatively high orbital eccentricities (up to 0.6). Recently, AC Her was observed to have a polar-aligned circumbinary disk. We perform hydrodynamic simulations to explore the impact of a polar-aligned disk on the eccentricity of a binary. For a binary system with central masses of 0.73 and 1.4 M⊙, we find that a disk with a total mass of 0.1 M⊙ can enhance the binary eccentricity from 0.2 to 0.7 within 5000 yr, or from 0.01 to 0.65 within 15,000 yr. Even if the disk mass is as low as 0.01 M⊙, the binary eccentricity grows within our simulation time while the system remains stable. These eccentricity variations are associated with the variations of the inclination between the disk and the binary orbit due to von Zeipel–Kozai–Lidov oscillations. The oscillations eventually damp and leave the binary eccentricity at a high value. The numerical results are in good agreement with analytical estimates. In addition, we examine the AC Her system and find that the disk mass should be on the order of 10‑3 M⊙ for the disk to remain polar.

Keywords: Stellar accretion disks, Post-asymptotic giant branch stars, Accretion, Binary stars
Modeling Solar Spectral Irradiance from Iron Lines Using the CODET Model Version 1.1. The COronal DEnsity and Temperature (CODET) model is a physics-based model. This model uses the relationship between the magnetic field, density, temperature, and extreme ultraviolet (EUV) emission. This model provides mean daily solar spectral irradiance (SSI) time series in EUV wavelengths in long timescales from days to solar cycles. The current manuscript presents the updated/new CODET model version 1.1. It uses observational data sets from the Solar Dynamics Observatory EUV Variability Experiment (SDO/EVE) MEGS-A at 28.4 and 21.1 nm wavelengths to obtain the goodness of fit between them and the modeled SSI from 2010 April 30 to 2014 May 26. The model described well observational data during that period, with less than 20% error in both wavelengths. Additionally, SSI predictions are provided using the new model parameters from 1996 July to 2024 October, where the Michelson Doppler Imager (MDI) and the Helioseismic and Magnetic Imager (HMI) photospheric magnetic field data are available. These predictions were compared with GOES/EUVS at 28.4 nm and mean daily values of the SDO Atmospheric Imaging Assembly at 21.1 nm data, with errors of ∼26% and 42% for 28.4 and 21.1 nm, respectively. The error analysis for model fitting and predictions shows how accurate the model predictions are. Thus, the CODET model provides a reliable estimate of the SSI time series in EUV wavelengths where no observational data are available, e.g., after the SDO/EVE MEGS-A era.

Keywords: Solar magnetic fields, Solar spectral irradiance, Solar corona