Sazuna/UAT_keywords huggingface dataset:
Anisotropic Turbulent Flows Observed in Above-the-loop-top Regions during Solar Flares. Solar flare above-the-loop-top (ALT) regions are vital for understanding solar eruptions and fundamental processes in plasma physics. Recent advances in three-dimensional (3D) magnetohydrodynamic (MHD) simulations have revealed unprecedented details on turbulent flows and MHD instabilities in flare ALT regions. Here, for the first time, we examine the observable anisotropic properties of turbulent flows in ALT by applying a flow-tracking algorithm on narrow-band extreme-ultraviolet images that are observed from the face-on viewing perspective. First, the results quantitatively confirm the previous observation that vertical motions dominate and that the anisotropic flows are widely distributed in the entire ALT region with the contribution from both upflows and downflows. Second, the anisotropy shows height-dependent features, with the most substantial anisotropy appearing at a certain middle height in ALT, which agrees well with the MHD modeling results where turbulent flows are caused by Rayleigh─Taylor-type instabilities in the ALT region. Finally, our finding suggests that supra-arcade downflows (SADs), the most prominently visible dynamical structures in ALT regions, are only one aspect of turbulent flows. Among these turbulent flows, we also report the antisunward-moving underdense flows that might develop due to MHD instabilities, as suggested by previous 3D flare models. Our results indicate that the entire flare fan displays group behavior of turbulent flows where the observational bright spikes and relatively dark SADs exhibit similar anisotropic characteristics.

Keywords: Magnetohydrodynamics, Solar flares, Plasma astrophysics, Solar physics, Solar activity, Magnetohydrodynamical simulations
Thermal Emission and Confirmation of the Frigid White Dwarf Exoplanet WD 1856+534 b. We report the detection of thermal emission from and confirm the planetary nature of WD 1856+534 b, the first transiting planet known to orbit a white dwarf (WD) star. Observations with JWST's Mid-Infrared Instrument reveal excess mid-infrared emission from the WD, consistent with a closely orbiting Jupiter-sized planet with a temperature of   K. We attribute this excess flux to the known giant planet in the system, making it the coldest exoplanet from which light has ever been directly observed. These measurements constrain the planet's mass to no more than six times that of Jupiter, confirming its planetary nature and ruling out previously unexcluded low-mass brown dwarf scenarios. WD 1856+534 b is now the first intact exoplanet confirmed within a WD's "forbidden zone," a region where planets would have been engulfed during the star's red giant phase. Its presence provides direct evidence that planetary migration into close orbits—including the habitable zone—around WDs is possible. With an age nearly twice that of the solar system and a temperature akin to our own gas giants, WD 1856+534 b demonstrates JWST's unprecedented ability to detect and characterize cold, mature exoplanets, opening new possibilities for imaging and characterizing these worlds in the solar neighborhood.

Keywords: Infrared excess, White dwarf stars, Extrasolar gaseous giant planets
Direct Evidence for r-process Nucleosynthesis in Delayed MeV Emission from the SGR 1806–20 Magnetar Giant Flare. The origin of heavy elements synthesized through the rapid neutron capture process (r-process) has been an enduring mystery for over half a century. J. Cehula et al. recently showed that magnetar giant flares, among the brightest transients ever observed, can shock heat and eject neutron star crustal material at high velocity, achieving the requisite conditions for an r-process. A. Patel et al. confirmed an r-process in these ejecta using detailed nucleosynthesis calculations. Radioactive decay of the freshly synthesized nuclei releases a forest of gamma-ray lines, Doppler broadened by the high ejecta velocities v ≳ 0.1c into a quasi-continuous spectrum peaking around 1 MeV. Here, we show that the predicted emission properties (light curve, fluence, and spectrum) match a previously unexplained hard gamma-ray signal seen in the aftermath of the famous 2004 December giant flare from the magnetar SGR 1806–20. This MeV emission component, rising to peak around 10 minutes after the initial spike before decaying away over the next few hours, is direct observational evidence for the synthesis of ∼10‑6 M⊙ of r-process elements. The discovery of magnetar giant flares as confirmed r-process sites, contributing at least ∼1%–10% of the total Galactic abundances, has implications for the Galactic chemical evolution, especially at the earliest epochs probed by low-metallicity stars. It also implicates magnetars as potentially dominant sources of heavy cosmic rays. Characterization of the r-process emission from giant flares by resolving decay line features offers a compelling science case for NASA's forthcoming COSI nuclear spectrometer, as well as next-generation MeV telescope missions.

Keywords: Magnetars, R-process, Gamma-ray transient sources, Nucleosynthesis
Biases from Missing a Small Planet in High Multiplicity Systems. In an era when we are charting multiple planets per system, one might wonder the extent to which "missing" (or failing to detect) a planet can skew our interpretation of the system architecture. We address this question with a simple experiment: starting from a large, homogeneous catalog, we remove planets and monitor how several well-defined metrics of the system architecture change. We first perform this test on a catalog of observed exoplanets. We then repeat our test on a catalog of synthetic planetary systems with underlying hyperparameters that have been fit to reproduce the observed systems as faithfully as possible (though imperfectly). For both samples, we find that the failure to detect one or more planets tends to create more irregularly spaced planets, whereas the planet mass similarity and coplanarity are essentially unaffected. One key difference between the synthetic and observed data sets is that the observed systems have more evenly spaced planets than the observation-bias-applied synthetic systems. Since our tests show that detection bias tends to increase irregularity in spacing, the even spacing in the observed planetary systems is likely astrophysical rather than the result of the Kepler missions' inherent detection biases. Our findings support the interpretation that planets in the same system have similar sizes and regular spacing and reinforce the need to develop an underlying model of planetary architectures that reproduces these observed patterns.

Keywords: Exoplanet astronomy, Exoplanets
New Estimates of the Spin and Accretion Rate of the Black Hole M87*. In this Letter, we use the imaging results of M87* from the Event Horizon Telescope (EHT) to calculate the rotational velocity of the inner edge of the accretion disk and find a value of ∼0.14c. We then calculate the dimensionless spin parameter, a, of the black hole, obtaining a value of a ∼ 0.8. We deduce that this is probably a lower limit. We go on to use the results of the EHT polarization study of the magnetic field direction in the accretion disk of M87* as a proxy for the direction of motion of the spiralling accreting matter in this highly ionized disk. This direction is defined by the vector sum of the tangential rotation velocity and the inward radial accretion velocity. We thus calculate the accretion velocity to be ∼(7 ± 0.7) × 107 ms‑1. We go on to estimate a range of values for the accretion rate from the inner disk to be ∼4 × 10‑5 to ∼4 × 10‑1 M⊙ yr‑1, and a range of values for the accretion power to be ∼1034–1038 J s‑1. This is the same range as the power of the jet, making it consistent with accretion-driven jet models.

Keywords: Supermassive black holes, Rotating black holes, Astrophysical black holes
Near-instantaneous Atmospheric Retrievals and Model Comparison with FASTER. In the era of the James Webb Space Telescope (JWST), the dramatic improvement in the spectra of exoplanetary atmospheres demands a corresponding leap forward in our ability to analyze them: atmospheric retrievals need to be performed on thousands of spectra, applying to each large ensembles of models (that explore atmospheric chemistry, thermal profiles, and cloud models) to identify the best one(s). In this limit, traditional Bayesian inference methods such as nested sampling become prohibitively expensive. We introduce Fast Amortized Simulation-based Transiting Exoplanet Retrieval (FASTER), a neural-network-based method for performing atmospheric retrieval and Bayesian model comparison at a fraction of the computational cost of classical techniques. We demonstrate that the marginal posterior distributions of all parameters within a model and the posterior probabilities of the models we consider match those computed using nested sampling both on mock spectra and for the real NIRSpec PRISM spectrum of WASP-39b. The true power of the FASTER framework comes from its amortized nature, which allows the trained networks to perform practically instantaneous Bayesian inference and model comparison over ensembles of spectra—real or simulated—at minimal additional computational cost. This offers valuable insight into the expected results of model comparison (e.g., distinguishing cloudy from cloud-free and isothermal from nonisothermal models), as well as their dependence on the underlying parameters, which is computationally unfeasible with nested sampling. This approach will constitute as large a leap in spectral analysis as the original retrieval methods based on Markov Chain Monte Carlo have proven to be.

Keywords: Bayesian statistics, Exoplanets, Neural networks
Polytropic Behavior in Corotating Interaction Regions: Evidence of Alfvénic Heating. Corotating interaction regions (CIRs) are recurring structures in the solar wind, characterized by interactions between fast and slow solar wind streams that compress and heat plasma. This study investigates the polytropic behavior of distinct regions in and around CIRs: uncompressed slow solar wind, compressed slow solar wind, compressed fast solar wind, and uncompressed fast solar wind. Using Wind spacecraft data and an established methodology for calculating the polytropic index (γ), we analyze 117 CIR events. Results indicate varying γ values across regions, with heating observed in compressed regions driven by Alfvén wave dissipation originating from fast streams. In the uncompressed fast solar wind, γ exceeds adiabatic values the most and correlates well with strong Alfvénic wave activity.

Keywords: Space plasmas, Corotating streams, Polytropes
Temporal Behavior and Latitudinal Relationships between Key Solar Parameters and Green Line Emissions in the Solar Corona. Understanding the link between solar parameters and their influence on green line emissions would help unravel the complexities of eruptive phenomena within the solar corona. This study explores the intricate relationship between green line emissions and various solar indicators, including flares, F10.7 cm flux, and sunspot numbers. Utilizing data from both ground-based and space-based sources spanning from 1996 to 2024, covering solar cycles 23 to 25, the investigation employs the multitaper and cross-correlation analyses. The study reveals distinct behaviors and contributions to green line emissions at low and high latitudes. The F10.7 cm radio flux exhibits zero lag with green line emissions, indicating that both are contemporaneously influenced by solar activity, as shown by their correlation with sunspot numbers. In contrast, B-, M-, and X-class flares typically act as precursors or aftermaths of such activity. C-class flares exhibit a pronounced positive correlation with the green line, causally linked to plasma dynamics, particularly at low latitudes. Sunspots, on the other hand, act as a leading and significant indicator of the green line with positive lag, preceding the emissions. The emissions are found to be an excellent indicator of solar activity, with an immediate response to the F10.7 cm flux and a delayed response to sunspot emergence. The differences in observed impacts could be attributed to the behavior of confined plasma within magnetic loops, influenced by factors such as solar magnetic configurations, differential rotation, and dynamo mechanisms. These factors collectively impact the global coronal structure and influence the green line across latitudes.

Keywords: Astronomy data analysis, Solar corona, Solar x-ray flares, Solar activity, Active solar corona
Detection of Methane in the Closest Extreme Metal-poor T Dwarf WISEA J181006.18‑101000.5. WISEA J181006.18‑101000.5 (WISE1810) is the nearest metal-poor ultracool dwarf to the Sun. It has a low effective temperature and has been classified as an extreme early-T subdwarf. However, methane, the characteristic molecule of the spectral class T, was not seen in the previous low-resolution spectrum. Using the 10.4 m Gran Telescopio Canarias, we collected a high-quality JHK-band intermediate-resolution R ≈ 5000 spectrum of WISE1810, in which 17 ± 6 ppm of methane is clearly detected, while carbon monoxide is absent. Based on a custom computed ATMO2020++ model, we estimated an effective temperature of 1000 ± 100 K, a high surface gravity of   dex, and a carbon abundance of [C/H] = ‑1.5 ± 0.2 dex, inferring [Fe/H] = ‑1.7 ± 0.2 dex. Potassium is not seen in our data, and the upper limits of the pseudoequivalent width of the J-band atomic lines are at least 25–60 times weaker than those measured from solar-metallicity early-T counterparts. We measured a heliocentric radial velocity of ‑83 ± 13 km s‑1, inferring that WISE1810 is more likely a thick-disk member. *Based on observations made with the Gran Telescopio Canarias.

Keywords: Brown dwarfs, Infrared spectroscopy, T subdwarfs, Atmospheric composition, Population II stars, Metallicity, T dwarfs
Discovery of the Seven-ring Polycyclic Aromatic Hydrocarbon Cyanocoronene (C<SUB>24</SUB>H<SUB>11</SUB>CN) in GOTHAM Observations of TMC-1. We present the synthesis and laboratory rotational spectroscopy of the seven-ring polycyclic aromatic hydrocarbon (PAH) cyanocoronene (C24H11CN) using a laser-ablation-assisted cavity-enhanced Fourier transform microwave spectrometer. A total of 71 transitions were measured and assigned between 6.8 and 10.6 GHz. Using these assignments, we searched for emission from cyanocoronene in the Green Bank Telescope (GBT) Observations of TMC-1: Hunting Aromatic Molecules project observations of the cold dark molecular cloud TMC-1 using the 100 m GBT. We detect a number of individually resolved transitions in ultrasensitive X-band observations and perform a Markov Chain Monte Carlo analysis to derive best-fit parameters, including a total column density of   at a temperature of  K. A spectral stacking and matched filtering analysis provides a robust 17.3σ significance to the overall detection. The derived column density is comparable to that of cyano-substituted naphthalene, acenaphthylene, and pyrene, defying the trend of decreasing abundance with increasing molecular size and complexity found for carbon chains. We discuss the implications of the detection for our understanding of interstellar PAH chemistry and highlight major open questions and next steps.

Keywords: Interstellar molecules, Radio spectroscopy, High resolution spectroscopy, Polycyclic aromatic hydrocarbons, Rotational spectroscopy, Cavity-enhanced Fourier-transform, Surveys, Microwave spectroscopy, Astrochemistry, Interstellar medium, Radio astronomy
The Ubiquity of Twisted Flux Ropes in the Quiet Sun. Models and observations have demonstrated that twisted flux ropes (TFRs) play a significant role in the structure and eruptive dynamics of active regions. Their role in the dynamics of the quiet Sun atmosphere has remained elusive, their fundamental relevance emerging mainly from theoretical models showing that they form and erupt as a result of flux cancellation. Here, Hinode high-resolution photospheric vector magnetic field measurements are integrated with advanced environment reconstruction models: TFRs develop on various scales and are associated with the appearance of mesospots. The developing TFRs contain sufficient free magnetic energy to match the requirements of the recently observed "campfires" discovered by Solar Orbiter in the quiet Sun. The free magnetic energy is found to be large enough to trigger eruptions, while the magnetic twist is large enough to trigger confined eruptions, heating the chromosphere. TFRs are also connected to larger-scale magnetic fields such as supergranulation loops, allowing the generation of Alfvén waves at the top of the chromosphere that can propagate along them. High-resolution magnetohydrodynamic simulations, incorporating subsurface dynamo activity at an unprecedented 30 km spatial resolution, confirm that TFRs are ubiquitous products of the permanent small-scale dynamo engine that feeds their formation, destabilization, eruption via flux emergence, submergence, and cancellation of their chromospheric feet, similar to the dynamics driving large-scale eruptive events. Future investigations, especially with the Daniel K. Inouye Solar Telescope and Solar Orbiter, will deepen our understanding of TFRs in the context of atmospheric heating.

Keywords: Solar physics
Discovery and Dynamics of the Nontransiting Planet Kepler-139f. Among the ways that an outer giant planet can alter the architecture of an inner planetary system is by tilting the orbits of the inner planets and reducing their mutual transit probabilities. Here, we report on an example of this phenomenon: we show that the Kepler-139 system contains a nontransiting planet just exterior to three transiting planets and interior to a giant planet. This newly discovered planet, Kepler-139f, has an orbital period of 355 ± 2 days and a mass of 36 ± 10 M⊕ based on transit-timing and radial-velocity data. Through dynamical simulations, we show that gravitational perturbations on planet f's orbit from the outer giant planet reduce the probability for a randomly located observer to see transits of all four inner planets. Thus, Kepler-139 illustrates the role that outer giant planets can play in the apparent truncation of compact systems of multiple transiting planets.

Keywords: Transits, Extrasolar gaseous giant planets, Exoplanets, Planetary dynamics
Cosmological Parameter Estimate from Persistent Radio Sources of Fast Radio Bursts. We introduce a novel method to constrain the Hubble constant (H0) by combining fast radio bursts (FRBs) and their persistent radio sources (PRSs) through the observationally validated Yang relation, Lν ∝ ∣RM∣, which links PRS luminosity to the rotation measure of the associated FRB. Using a mock sample of PRSs, we demonstrate that the Yang relation can help to unravel the degeneracies among H0, baryon density parameter Ωb, and baryon fraction in the intergalactic medium fIGM in the traditional approach of using dispersion measure only to perform cosmological analyses. Our method employs a two-stage Markov Chain Monte Carlo analysis to constrain H0. Using the available data of six observed PRS systems, we obtain a preliminary constraint of H0 = 75 ± 30 km s‑1 Mpc‑1. We briefly discuss possible refinements of the method by reducing residual degeneracies and systematic uncertainties using future data and physical modeling. Our results indicate that the Yang relation can potentially become a new probe for performing FRB cosmology.

Keywords: Cosmological parameters, Hubble constant, Radio bursts, Radio continuum emission, Radio sources
On the Potential Cosmogenic Origin of the Ultra-high-energy Event KM3-230213A. On 2023 February 13, the KM3NeT/ARCA telescope observed a track-like event compatible with a ultra-high-energy muon with an estimated energy of 120 PeV, produced by a neutrino with an even higher energy, making it the most energetic neutrino event ever detected. A diffuse cosmogenic component is expected to originate from the interactions of ultra-high-energy cosmic rays with ambient photon and matter fields. The flux level required by the KM3NeT/ARCA event is, however, in tension with the standard cosmogenic neutrino predictions based on the observations collected by the Pierre Auger Observatory and Telescope Array over the last decade of the ultra-high-energy cosmic rays above the ankle (hence from the local Universe, z ≲ 1). We show here that both observations can be reconciled by extending the integration of the equivalent cosmogenic neutrino flux up to a redshift of  zmax=6  and considering either source evolution effects or the presence of a subdominant independent proton component in the ultra-high-energy cosmic-ray flux, thus placing constraints on known cosmic accelerators.

Keywords: Neutrino astronomy, Non-thermal radiation sources, Ultra-high-energy cosmic radiation
Detection of Deuterated Hydrocarbon Nanoparticles in the Whirlpool Galaxy, M51. Deuteration of hydrocarbon material, including polycyclic aromatic hydrocarbons (PAHs), has been proposed to account for the low gas-phase abundances of D in the interstellar medium (ISM). JWST spectra of four star-forming regions in M51 show an emission feature, with central wavelength ∼4.647 μm and FWHM 0.0265 μm, corresponding to the C–D stretching mode in aliphatic hydrocarbons. The emitting aliphatic material is estimated to have (D/H)aliph. ≈0.17 ± 0.02—a factor of ∼104 enrichment relative to the overall ISM. On ∼50 pc scales, deuteration levels toward four H II regions in M51 are 2–3 times higher than in the Orion Bar photodissociation region (PDR), with implications for the processes responsible for the formation and evolution of hydrocarbon nanoparticles, including PAHs. The deuteration of the aliphatic material is found to anticorrelate with helium ionization in the associated H II, suggesting that harsh far-UV radiation may act to lower the deuteration of aliphatics in PDRs near massive stars. No evidence is found for deuteration of aromatic material, with (D/H)arom. ≲ 0.016: deuteration of the aliphatic material exceeds that of the aromatic material by at least a factor of 10. The observed levels of deuteration may account for the depletion of D observed in the Galactic ISM. If so, the 4.65 μm feature may be detectable in absorption.

Keywords: Interstellar dust, Interstellar line emission, Interstellar abundances, Emission nebulae, Interstellar medium, Interstellar extinction, Galaxies
An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus. We report the discovery of an actinide-boost, very metal-poor ( ), r-process-enhanced ( ) star, LAMOST J0804+5740, within the Gaia-Sausage-Enceladus (GSE). Based on the high-resolution (R ∼ 36,000 and 60,000) and high signal-to-noise ratio spectra obtained with the High Dispersion Spectrograph on the Subaru Telescope, the abundances of 48 species are determined. Its   establishes it as the first confirmed actinide-boost star within the GSE. Comparative analysis of its abundance pattern with theoretical r-process models reveals that the magnetorotationally driven jet supernova r-process model with   = 0.2 provides the best fit and successfully reproduces the actinide-boost signature. Kinematic analysis of actinide-boost stars reveals that approximately two-thirds of them are classified as ex situ stars, suggesting that actinide-boost stars are more likely to originate from accreted dwarf galaxies. As the first actinide-boost star identified within the GSE, J0804+5740 will provide valuable insights into r-process nucleosynthesis in accreted dwarf galaxies like the GSE, especially on the production of the heaviest elements.

Keywords: Chemically peculiar giant stars, Stellar abundances, R-process, Galactic archaeology, Milky Way stellar halo