Sazuna/UAT_keywords huggingface dataset:
Synchrotron Radiation Dominates the Extremely Bright GRB 221009A. The brightest gamma-ray burst, GRB 221009A, has spurred numerous theoretical investigations, with particular attention paid to the origins of ultrahigh-energy TeV photons during the prompt phase. However, analyzing the mechanism of radiation of photons in the ~MeV range has been difficult because the high flux causes pileup and saturation effects in most GRB detectors. In this Letter, we present systematic modeling of the time-resolved spectra of the GRB using unsaturated data obtained from the Fermi Gamma-ray Burst Monitor (precursor) and SATech-01/GECAM-C (main emission and flare). Our approach incorporates the synchrotron radiation model, which assumes an expanding emission region with relativistic speed and a global magnetic field that decays with radius, and successfully fits such a model to the observational data. Our results indicate that the spectra of the burst are fully in accordance with a synchrotron origin from relativistic electrons accelerated at a large emission radius. The lack of thermal emission in the prompt emission spectra supports a Poynting flux-dominated jet composition.

Keywords: Gamma-ray bursts
Constraints on the Cosmological Coupling of Black Holes from the Globular Cluster NGC 3201. Globular clusters are among the oldest stellar populations in the Milky Way; consequently, they also host some of the oldest known stellar-mass black holes, providing insight into black hole formation and evolution in the early (z ≳ 2) universe. Recent observations of supermassive black holes in elliptical galaxies have been invoked to suggest the possibility of a cosmological coupling between astrophysical black holes and the surrounding expanding universe, offering a mechanism for black holes to grow over cosmic time and potentially explaining the origin of dark energy. In this paper, I show that the mass functions of the two radial velocity black hole candidates in NGC 3201 place strong constraints on the cosmologically coupled growth of black holes. In particular, the amount of coupling required to explain the origin of dark energy would either require both NGC 3201 black holes to be nearly face on (a configuration with probability of at most 10-4) or one of the BHs would need to have formed with a mass below that of the most massive neutron stars (2.2 M ⊙). This emphasizes that these and other detached black hole-star binaries can serve not only as laboratories for compact object and binary astrophysics but as constraints on the long-term evolution of astrophysical black holes.

Keywords: Dark energy, Stellar mass black holes, Expanding universe
The Efficiency of Electron Acceleration during the Impulsive Phase of a Solar Flare. Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a lack of observational constraints related to conditions in the primary acceleration region itself. Accelerated electrons with energies above ~20 keV are revealed by hard X-ray (HXR) bremsstrahlung emission, while accelerated electrons with even higher energies manifest themselves through radio gyrosynchrotron emission. Here, we show, for a well-observed flare on 2017 September 10, that a combination of RHESSI HXR and and the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV observations provides a robust estimate of the fraction of the ambient electron population that is accelerated at a given time, with an upper limit of ≲10-2 on the number density of nonthermal (≥20 keV) electrons, expressed as a fraction of the number density of ambient protons in the same volume. This upper limit is about 2 orders of magnitude lower than previously inferred from microwave observations of the same event. Our results strongly indicate that the fraction of accelerated electrons in the coronal region at any given time is relatively small but also that the overall duration of the HXR emission requires a steady resupply of electrons to the acceleration site. Simultaneous measurements of the instantaneous accelerated electron number density and the associated specific electron acceleration rate provide key constraints for a quantitative study of the mechanisms leading to electron acceleration in magnetic reconnection events.

Keywords: Solar flares, Solar physics, Solar x-ray flares, Solar activity, Solar radio flares
External Inverse-compton and Proton Synchrotron Emission from the Reverse Shock as the Origin of VHE Gamma Rays from the Hyper-bright GRB 221009A. The detection of the hyper-bright gamma-ray burst (GRB) 221009A enables us to explore the nature of the GRB emission and the origin of very high-energy gamma rays. We analyze the Fermi Large Area Telescope (Fermi-LAT) data of this burst and investigate the GeV-TeV emission in the framework of the external reverse-shock model. We show that the early ~1-10 GeV emission can be explained by the external inverse-Compton mechanism via upscattering MeV gamma rays by electrons accelerated at the reverse shock, in addition to the synchrotron self-Compton component. The predicted early optical flux could have been brighter than that of the naked-eye GRB 080319B. We also show that proton synchrotron emission from accelerated ultrahigh-energy cosmic rays (UHECRs) is detectable and could potentially explain ≳TeV photons detected by LHAASO or constrain the UHECR acceleration mechanism. Our model suggests that the detection of ${ \mathcal O }(10\,\mathrm{TeV})$ photons with energies up to ~18 TeV is possible for reasonable models of the extragalactic background light without invoking new physics and predicts anticorrelations between MeV photons and TeV photons, which can be tested with the LHAASO data.

Keywords: Gamma-ray bursts, High energy astrophysics, Gamma-ray sources, Relativistic jets, Non-thermal radiation sources, Gamma-ray astronomy
Flares, Jets, and Quasiperiodic Outbursts from Neutron Star Merger Remnants. Using numerical relativity simulations with a subgrid dynamo prescription to generate strong initial magnetic fields, we investigate the possibility of launching a jet-like outflow from the hypermassive neutron star (HMNS) during the early stages of the merger, prior to the remnant's collapse to a black hole. We demonstrate that buoyant instabilities in the strongly magnetized HMNS can lead to a periodic emission of powerful electromagnetic flares shortly after the merger. These are followed by a collimated mildly relativistic outflow. Both types of outflows feature quasiperiodic kilohertz substructure. These early-time outflows may power precursors to short-duration gamma-ray bursts (sGRBs) or in some cases the entire sGRB. While the overall temporal power spectrum we find broadly agrees with the one recently reported for quasiperiodic oscillations in the sGRB GRB910711, our simulations suggest that the periodic electromagnetic substructure is dominated by magnetohydrodynamic shearing processes rather than correlating with the corresponding postmerger gravitational-wave signal.

Keywords: Neutron stars, Gamma-ray bursts, Stellar flares, Gravitational waves, Asteroseismology, Magnetohydrodynamical simulations
The Game of Life on a Magnetar Crust: From Gamma-Ray Flares to FRBs. This Letter presents a model to unify the diverse range of magnetar activity, through the building and release of elastic stress from the crust. A cellular automaton drives both local and global yielding of the crust, leading to braiding of coronal loops and energy release. The model behaves like a real magnetar in many ways: giant flares and small bursts both occur, as well as periods of quiescence whose typical duration is either ≲1 yr or ~10-30 yr. The burst energy distribution broadly follows an earthquake-like power law over the energy range 1040-1045 erg. The local nature of coronal loops allows for the possibility of high-energy and fast radio bursts from the same magnetar. Within this paradigm, magnetar observations can be used to constrain the poorly understood mechanical properties of the neutron-star crust.

Keywords: Neutron stars, Magnetars, Radio bursts, X-ray bursts
Multithermal Jet Formation Triggered by Flux Emergence. Flux emergence is responsible for various solar eruptions. Combining observation and simulations, we investigate the influence of flux emergence at one footpoint of an arcade on coronal rain as well as induced eruptions. The emergence changes the pressure in the loops, and the internal coronal rain all moves to the other side. The emerging flux reconnects with the overlying magnetic field, forming a current sheet and magnetic islands. The plasma is ejected outwards and heated, forming a cool jet ~6000 K and a hot X-ray jet ~4 million Kelvin (MK) simultaneously. The jet dynamical properties agree very well between observation and simulation. In the simulation, the jet also displays transverse oscillations with a period of 8 minutes, in a so-called whiplike motion. The movement of the jet and dense plasmoids changes the configuration of the local magnetic field, facilitating the occurrence of the Kelvin-Helmholtz instability, and vortex-like structures form at the boundary of the jet. Our simulation clearly demonstrates the effect of emergence on coronal rain, the dynamical details of reconnecting plasmoid chains, the formation of multithermal jets, and the cycling of cool mass between the chromosphere and the corona.

Keywords: Solar atmosphere, Solar magnetic flux emergence, Solar prominences, Solar activity, Magnetohydrodynamical simulations
First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions. Low-energy cosmic rays (&lt;1 TeV) are a pivotal source of ionization of the interstellar medium, where they play a central role in determining the gas chemical composition and drastically influence the formation of stars and planets. Over the past few decades, H3 + absorption line observations in diffuse clouds have provided reliable estimates of the cosmic-ray ionization rate relative to H2 ( ${\zeta }_{{{\rm{H}}}_{2}}^{\mathrm{ion}}$ ). However, in denser clouds, where stars and planets form, this method is often inefficient due to the lack of H3 + rotational transitions. The ${\zeta }_{{{\rm{H}}}_{2}}^{\mathrm{ion}}$ estimates are, therefore, still provisional in this context and represent one of the least understood components when it comes to defining general models of star and planet formation. In this Letter, we present the first high-resolution maps of the ${\zeta }_{{{\rm{H}}}_{2}}^{\mathrm{ion}}$ in two high-mass clumps obtained with a new analytical approach recently proposed to estimate the ${\zeta }_{{{\rm{H}}}_{2}}^{\mathrm{ion}}$ in the densest regions of molecular clouds. We obtain $\langle {\zeta }_{{{\rm{H}}}_{2}}^{\mathrm{ion}}\rangle $ that span from 3 × 10-17 to 10-16 s-1, depending on the different distribution of the main ion carriers, in excellent agreement with the most recent cosmic-ray propagation models. The cores belonging to the same parental clump show comparable ${\zeta }_{{{\rm{H}}}_{2}}^{\mathrm{ion}}$ , suggesting that the ionization properties of prestellar regions are determined by global rather than local effects. These results provide important information for the chemical and physical modeling of star-forming regions.

Keywords: Interstellar line emission, Star forming regions, Massive stars, Astrochemistry, Star formation, Interstellar medium, Cosmic rays
Conclusive Evidence for a Population of Water Worlds around M Dwarfs Remains Elusive. The population of small, close-in exoplanets is bifurcated into super-Earths and sub-Neptunes. We calculate physically motivated mass-radius relations for sub-Neptunes, with rocky cores and H/He-dominated atmospheres, accounting for their thermal evolution, irradiation, and mass loss. For planets ≲10 M ⊕, we find that sub-Neptunes retain atmospheric mass fractions that scale with planet mass and show that the resulting mass-radius relations are degenerate with results for "water worlds" consisting of a 1:1 silicate-to-ice composition ratio. We further demonstrate that our derived mass-radius relation is in excellent agreement with the observed exoplanet population orbiting M dwarfs and that planet mass and radii alone are insufficient to determine the composition of some sub-Neptunes. Finally, we highlight that current exoplanet demographics show an increase in the ratio of super-Earths to sub-Neptunes with both stellar mass (and therefore luminosity) and age, which are both indicative of thermally driven atmospheric escape processes. Therefore, such processes should not be ignored when making compositional inferences in the mass-radius diagram.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheric evolution
IXPE Observations of the Quintessential Wind-accreting X-Ray Pulsar Vela X-1. The radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up to 80%. However, phase-resolved and energy-resolved polarimetry of X-ray pulsars is required in order to test different models and to shed light on the emission processes and the geometry of the emission region. Here we present the first results of the observations of the accreting X-ray pulsar Vela X-1 performed with the Imaging X-ray Polarimetry Explorer. Vela X-1 is considered to be the archetypal example of a wind-accreting, high-mass X-ray binary system, consisting of a highly magnetized neutron star accreting matter from its supergiant stellar companion. The spectropolarimetric analysis of the phase-averaged data for Vela X-1 reveals a polarization degree (PD) of 2.3% ± 0.4% at the polarization angle (PA) of -47.°3 ± 5.°4. A low PD is consistent with the results obtained for other X-ray pulsars and is likely related to the inverse temperature structure of the neutron star atmosphere. The energy-resolved analysis shows the PD above 5 keV reaching 6%-10% and a ~90° difference in the PA compared to the data in the 2-3 keV range. The phase-resolved spectropolarimetric analysis finds a PD in the range 0%-9% with the PA varying between -80° and 40°.

Keywords: Neutron stars, Accretion, High mass x-ray binary stars, Pulsars, Starlight polarization, Magnetic fields
GRB 211211A: A Neutron Star-White Dwarf Merger?. The gamma-ray burst GRB 211211A and its associated kilonova-like emission were reported recently. A significant difference between this association event and GRB 170817A/AT 2017gfo is that GRB 211211A has a very long duration. In this Letter, we show that this association event may arise from a neutron star-white dwarf (NS-WD) merger if the central engine leaves a magnetar behind. Within the NS-WD merger, the main burst of GRB 211211A could be produced by magnetic bubble eruptions from toroidal magnetic field amplification of the premerger NS. This toroidal field amplification can be induced by the runaway accretion from the WD debris disk if the disk is in low initial entropy and efficient wind, while the extended emission of GRB 211211A is likely involved with magnetic propelling. The observed energetics and duration of the prompt emission of GRB 211211A can be fulfilled in comparison with those of accretion in a hydrodynamical thermonuclear simulation, as long as the WD has a mass ≳1M ⊙. Moreover, if the X-ray plateau in GRB afterglows is due to the magnetar spin-down radiation, GRB optical afterglows and kilonova-like emission can be jointly well modeled combining the standard forward shock with the radioactive decay power of 56Ni adding a rotational power input from the postmerger magnetar.

Keywords: Neutron stars, Gamma-ray bursts, White dwarf stars, Compact binary stars, Magnetars
Intermittency of Magnetic Discontinuities in the Near-Sun Solar Wind Turbulence. The intermittency domain is in the magnetohydrodynamic inertial range but just above the dissipation range and contains the intermittent structures that influence the spectral index. However, the nature of these structures is still under debate and how they affect the higher-order scaling behavior in the near-Sun solar wind turbulence remains to be investigated. Here we use the magnetic field data measured by Parker Solar Probe in the near-Sun solar wind. We identify the intermittency by partial variance of increments method and conduct the multiorder structure functions analyses in the intermittency domain before and after removing the intermittency. We also perform for the first time the scaling analyses on the fluctuations of magnetic field direction given by the rotational angle $\theta ={\cos }^{-1}({{\boldsymbol{B}}}_{1}\cdot {{\boldsymbol{B}}}_{2})/| {{\boldsymbol{B}}}_{1}| | {{\boldsymbol{B}}}_{2}| $ , in which B 1 and B 2 are the magnetic fields measured at two instants. We find that the multifractal scaling of the magnetic field could be predicted by the log-Poisson intermittency model with 2D sheetlike structures and a simple Kolmogorov -5/3 monoscaling recovers after the removal of the intermittency. We also find a similar behavior for the scalings of θ, suggesting that magnetic discontinuities are involved in the energy transfer process of solar wind turbulence.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Solar wind, Heliosphere
Solar System-scale Interferometry on Fast Radio Bursts Could Measure Cosmic Distances with Subpercent Precision. The light from an extragalactic source at a distance d will arrive at detectors separated by 100 au at times that differ by as much as 120(d/100 Mpc)-1 nanoseconds because of the curvature of the wave front. At gigahertz frequencies, the arrival time difference of a point source can be determined to better than a nanosecond with interferometry. If the spacetime positions of the detectors are known to a few centimeters, comparable to the accuracy to which very long baseline interferometry baselines and global navigation satellite systems (GNSS) geolocations are constrained, nanosecond timing would allow competitive cosmological constraints. We show that a four-detector constellation at Solar radii of ≳10 au could measure geometric distances to individual sources with subpercent precision. The precision increases quadratically with baseline length. Fast radio bursts (FRBs) are the only known bright extragalactic radio source that are sufficiently point-like for this experiment, and the simplest approach would target the population of repeating FRBs. Galactic scattering limits the timing precision at ≲3 GHz, whereas at higher frequencies the precision is set by removing the differential dispersion between the detectors. Furthermore, for baselines greater than 100 au, Shapiro time delays limit the precision, but their effect can be cleaned at the cost of two additional detectors. Outer solar system accelerations that result in ~1 cm uncertainty in detector positions could be corrected for with weekly GNSS-like trilaterations between members of the constellation. The proposed interferometer would not only provide a geometric constraint on the Hubble constant, but also could advance solar system, pulsar, and gravitational wave science.

Keywords: Cosmology, Cosmological constant experiments, Cosmological parameters
Early Results from GLASS-JWST. XIV. A Spectroscopically Confirmed Protocluster 650 Million Years after the Big Bang. We present the spectroscopic confirmation of a protocluster at z = 7.88 behind the galaxy cluster Abell 2744 (hereafter A2744-z7p9OD). Using JWST NIRSpec, we find seven galaxies within a projected radius of 60 kpc. Although the galaxies reside in an overdensity around ≳20× greater than a random volume, they do not show strong Lyα emission. We place 2σ upper limits on the rest-frame equivalent width &lt;16-28 Å. Based on the tight upper limits to the Lyα emission, we constrain the volume-averaged neutral fraction of hydrogen in the intergalactic medium to be x HI &gt; 0.45 (68% C I). Using an empirical M UV-M halo relation for individual galaxies, we estimate that the total halo mass of the system is ≳4 × 1011 M ⊙. Likewise, the line-of-sight velocity dispersion is estimated to be 1100 ± 200 km s-1. Using an empirical relation, we estimate the present-day halo mass of A2744-z7p9OD to be ~2 × 1015 M ⊙, comparable to the Coma cluster. A2744-z7p9OD is the highest redshift spectroscopically confirmed protocluster to date, demonstrating the power of JWST to investigate the connection between dark-matter halo assembly and galaxy formation at very early times with medium-deep observations at &lt;20 hr total exposure time. Follow-up spectroscopy of the remaining photometric candidates of the overdensity will further refine the features of this system and help characterize the role of such overdensities in cosmic reionization.

Keywords: Galaxy clusters, Reionization, Galaxies, Protoclusters
Early Results from GLASS-JWST. XV. Properties of the Faintest Red Sources in the NIRCAM Deep Fields. We present a first look at the reddest 2–5 μm sources found in deep images from the GLASS Early Release Science program. We undertake a general search, i.e., not looking for any particular spectral signatures, for sources detected only in bands redder than is reachable with the Hubble Space Telescope, and which would likely not have been identified in pre-JWST surveys. We search for sources down to AB ∼27 (corresponding to &gt;10σ detection threshold) in any of the F200W to F444W filters, with a &gt;1 magnitude excess relative to F090W to F150W bands. Fainter than F444W &gt;25 we find 56 such sources of which 37 have reasonably constrained spectral energy distributions to which we can fit photometric redshifts. We find the majority of this population (∼65%) as 2 &lt; z &lt; 6 star-forming low-attenuation galaxies that are faint at rest-frame ultraviolet-optical wavelengths, have stellar masses 108.5–109.5 M ⊙, and have observed fluxes at &gt;2 μm boosted by a combination of the Balmer break and emission lines. The typical implied rest equivalent widths are ∼200 Å with some extreme objects up to ∼1000 Å. This is in contrast with brighter magnitudes where the red sources tend to be z &lt; 3 quiescent galaxies and dusty star-forming objects. Our general selection criteria for red sources allow us to independently identify other phenomena as diverse as extremely low-mass (∼108 M ⊙) quiescent galaxies at z &lt; 1, recovering recently identified z &gt; 11 galaxies and a very cool brown dwarf.

Keywords: High-redshift galaxies
Early Results from GLASS-JWST. XVI. Discovering a Bluer z   4-7 Universe through UV Slopes. We use the GLASS-JWST Early Release Science NIRCam parallel observations to provide a first view of the UV continuum properties of NIRCam/F444W selected galaxies at 4 &lt; z &lt; 7. By combining multiwavelength NIRCam observations, we constrain the UV continuum slope for a sample of 401 galaxies with stringent quality controls. We find that &gt;99% of the galaxies are blue star-forming galaxies with very low levels of dust (Av  β  ~ 0.01 ± 0.33). We find no statistically significant correlation for UV slope with redshift or UV magnitude. However, we find that in general galaxies at higher redshifts and fainter UV magnitudes have steeper UV slopes. We find a statistically significant correlation for UV slope with stellar mass, with galaxies with higher stellar mass showing shallower UV slopes. Individual fits to some of our galaxies reach the bluest UV slopes of β ~ -3.1 allowed by stellar population models used in this analysis. Therefore, it is likely that stellar population models with a higher amount of Lyman continuum leakage, active galactic nucleus effects, and/or Population III contributions are required to accurately reproduce the rest-UV and optical properties of some of our bluest galaxies. This dust-free early view confirms that our current cosmological understanding of gradual mass + dust buildup of galaxies with cosmic time is largely accurate to describe the ~0.7-1.5 Gyr age window of the universe. The abundance of a large population of UV faint dust-poor systems may point to a dominance of low-mass galaxies at z &gt; 6 playing a vital role in cosmic reionization.

Keywords: High-redshift galaxies, Galaxy evolution