Sazuna/UAT_keywords huggingface dataset:
Transonic Turbulence and Density Fluctuations in the Near-Sun Solar Wind. We use in situ measurements from the first 19 encounters of Parker Solar Probe and the most recent five encounters of Solar Orbiter to study the evolution of the turbulent sonic Mach number Mt (the ratio of the amplitude of velocity fluctuations to the sound speed) with radial distance and its relationship to density fluctuations. We focus on the near-Sun region with radial distances ranging from about 11 to 80 R⊙. Our results show that (1) the turbulent sonic Mach number Mt gradually moves toward larger values as it approaches the Sun, until at least 11 R⊙, where Mt is much larger than the previously observed value of 0.1 at and above 0.3 au; (2) transonic turbulence with Mt ∼ 1 is observed in situ for the first time and is found mostly near the Alfvén critical surface; (3) Alfvén Mach number of the bulk flow MA shows a strong correlation with the plasma beta, indicating that most of the observed sub-Alfvénic intervals correspond to a low-beta plasma; (4) the scaling relation between density fluctuations and Mt gradually changes from a linear scaling at larger radial distances to a quadratic scaling at smaller radial distances; and (5) transonic turbulence is more compressible than subsonic turbulence, with enhanced density fluctuations and slightly flatter spectra than subsonic turbulence. A systematic understanding of compressible turbulence near the Sun is necessary for future solar wind modeling efforts.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind
Promise and Peril: Stellar Contamination and Strict Limits on the Atmosphere Composition of TRAPPIST-1 c from JWST NIRISS Transmission Spectra. Attempts to probe the atmospheres of rocky planets around M dwarfs present both promise and peril. While their favorable planet-to-star radius ratios enable searches for even thin secondary atmospheres, their high activity levels and high-energy outputs threaten atmosphere survival. Here we present the 0.6–2.85 μm transmission spectrum of the 1.1 R⊕, ∼ 340 K rocky planet TRAPPIST-1 c obtained over two JWST NIRISS/SOSS transit observations. Each of the two spectra displays 100–500 ppm signatures of stellar contamination. Despite being separated by 367 days, the retrieved spot and facula properties are consistent between the two visits, resulting in nearly identical transmission spectra. Jointly retrieving for stellar contamination and a planetary atmosphere reveals that our spectrum can rule out hydrogen-dominated, ≲300× solar metallicity atmospheres with effective surface pressures down to 10 mbar at the 3σ level. For high mean molecular weight atmospheres, where O2 or N2 is the background gas, our spectrum disfavors partial pressures of more than ∼10 mbar for H2O, CO, NH3, and CH4 at the 2σ level. Similarly, under the assumption of a 100% H2O, NH3, CO, or CH4 atmosphere, our spectrum disfavors thick, &gt;1-bar atmospheres at the 2σ level. These nondetections of spectral features are in line with predictions that even heavier, CO2-rich atmospheres would be efficiently lost on TRAPPIST-1 c given the cumulative high-energy irradiation experienced by the planet. Our results further stress the importance of robustly accounting for stellar contamination when analyzing JWST observations of exo-Earths around M dwarfs, as well as the need for high-fidelity stellar models to search for the potential signals of thin secondary atmospheres.

Keywords: Extrasolar rocky planets, Exoplanets, Planetary atmospheres, Low mass stars, Exoplanet atmospheres
NuSTAR Observations of a Varying-flux Quasar in the Epoch of Reionization. With enough X-ray flux to be detected in a 160 s scan by SRG/eROSITA, the z = 6.19 quasar CFHQS J142952+544717 is, by far, the most luminous X-ray source known at z &gt; 6. We present deep (245 ks) NuSTAR observations of this source; with ∼180 net counts in the combined observations, CFHQS J142952+544717 is the most distant object ever observed by the observatory. Fortuitously, this source was independently observed by Chandra ∼110 days earlier, enabling the identification of two nearby (30″ and 45″ away), fainter X-ray sources. We jointly fit both Chandra and NuSTAR observations—self-consistently including interloper sources—and find that, to greater than 90% confidence, the observed 3–7 keV flux varied by a factor of ∼2.6 during that period, corresponding to approximately two weeks in the quasar rest frame. This brightening is one of the most extreme instances of statistically significant X-ray variability seen in the Epoch of Reionization. We discuss possible scenarios that could produce such rapid change, including X-ray emission from jets too faint at radio frequencies to be observed.

Keywords: X-ray astronomy, Quasars, Radio loud quasars, X-ray quasars, Time domain astronomy
A Possible Metal-dominated Atmosphere below the Thick Aerosols of GJ 1214 b Suggested by Its JWST Panchromatic Transmission Spectrum. GJ 1214b is the archetype sub-Neptune for which thick aerosols have prevented us from constraining its atmospheric properties for over a decade. In this study, we leverage the panchromatic transmission spectrum of GJ 1214b established by the Hubble Space Telescope (HST) and JWST to investigate its atmospheric properties using a suite of atmospheric radiative transfer, photochemistry, and aerosol microphysical models. We find that the combined HST, JWST/NIRSpec, and JWST/MIRI spectrum can be well explained by atmospheric models with an extremely high metallicity of [M/H] ∼ 3.5 and an extremely high haze production rate of Fhaze ∼ 10‑8 to 10‑7 g cm‑2 s‑1. Such high atmospheric metallicity is suggested by the relatively strong CO2 feature compared to the haze absorption feature or the CH4 feature in the NIRSpec-G395H bandpass of 2.5–5 μm. The flat 5–12 μm MIRI spectrum also suggests a small scale height with a high atmospheric metallicity that is needed to suppress a prominent ∼6 μm haze feature. We tested the sensitivity of our interpretation to various assumptions for uncertain haze properties, such as optical constants and production rate, and all models tested here consistently suggest extremely high metallicity. Thus, we conclude that GJ 1214b likely has a metal-dominated atmosphere where hydrogen is no longer the main atmospheric constituent. We also find that different assumptions for the haze production rate lead to distinct inferences for the atmospheric C/O ratio. We stress the importance of high-precision follow-up observations to confirm the metal-dominated atmosphere, as it challenges the conventional understanding of interior structure and evolution of sub-Neptunes.

Keywords: Exoplanet atmospheric composition , Exoplanets, Exoplanet structure, Exoplanet formation, Exoplanet atmospheres, Exoplanet atmospheric structure
On the Lunar Origin of Near-Earth Asteroid 2024 PT5. The near-Earth asteroid (NEA) 2024 PT5 is on an Earth-like orbit that remained in Earth's immediate vicinity for several months at the end of 2024. PT5's orbit is challenging to populate with asteroids originating from the main belt and is more commonly associated with rocket bodies mistakenly identified as natural objects or with debris ejected from impacts on the Moon. We obtained visible and near-infrared reflectance spectra of PT5 with the Lowell Discovery Telescope and NASA Infrared Telescope Facility on 2024 August 16. The combined reflectance spectrum matches lunar samples but does not match any known asteroid types—it is pyroxene-rich, while asteroids of comparable spectral redness are olivine-rich. Moreover, the amount of solar radiation pressure observed on the PT5 trajectory is orders of magnitude lower than what would be expected for an artificial object. We therefore conclude that 2024 PT5 is ejecta from an impact on the Moon, thus making PT5 the second NEA suggested to be sourced from the surface of the Moon. While one object might be an outlier, two suggest that there is an underlying population to be characterized. Long-term predictions of the position of 2024 PT5 are challenging due to the slow Earth encounters characteristic of objects in these orbits. A population of near-Earth objects that are sourced by the Moon would be important to characterize for understanding how impacts work on our nearest neighbor and for identifying the source regions of asteroids and meteorites from this understudied population of objects on very Earth-like orbits.

Keywords: Asteroid dynamics, The Moon, Asteroids, Earth-moon system
The Hubble Tension in Our Own Backyard: DESI and the Nearness of the Coma Cluster. The Dark Energy Spectroscopic Instrument (DESI) collaboration measured a tight relation between the Hubble constant (H0) and the distance to the Coma cluster using the fundamental plane (FP) relation of the deepest, most homogeneous sample of early-type galaxies. To determine H0, we measure the distance to Coma by several independent routes, each with its own geometric reference. We measure the most precise distance to Coma from 13 Type Ia supernovae (SNe Ia) in the cluster with a mean standardized brightness of   mag. Calibrating the absolute magnitude of SNe Ia with the Hubble Space Telescope (HST) distance ladder yields DComa = 98.5 ± 2.2 Mpc, consistent with its canonical value of 95–100 Mpc. This distance results in H0 = 76.5 ± 2.2 km s‑1 Mpc‑1 from the DESI FP relation. Inverting the DESI relation by calibrating it instead to the Planck+ΛCDM value of H0 = 67.4 km s‑1 Mpc‑1 implies a much greater distance to Coma, DComa = 111.8 ± 1.8 Mpc, 4.6σ beyond a joint, direct measure. Independent of SNe Ia, the HST Key Project FP relation as calibrated by Cepheids, the tip of the red giant branch from JWST, or HST near-infrared surface brightness fluctuations all yield DComa &lt; 100 Mpc, in joint tension themselves with the Planck-calibrated route at &gt;3σ. From a broad array of distance estimates compiled back to 1990, it is hard to see how Coma could be located as far as the Planck+ΛCDM expectation of &gt;110 Mpc. By extending the Hubble diagram to Coma, a well-studied location in our own backyard whose distance was in good accord well before the Hubble tension, DESI indicates a more pervasive conflict between our knowledge of local distances and cosmological expectations. We expect future programs to refine the distance to Coma and nearer clusters to help illuminate this new local window on the Hubble tension.

Keywords: Distance measure, Type Ia supernovae, Distance indicators
Radial Evolution of Interplanetary Shock Properties with Heliospheric Distance: Observations from Parker Solar Probe. We present a comprehensive analysis of 66 interplanetary shocks observed by the Parker Solar Probe between 2018 November and 2024 January. Among these, 33 events fulfilled the Rankine–Hugoniot (R-H) conditions, ensuring reliable asymptotic plasma parameter solutions. The remaining 33 events could not be confirmed by the standard R-H approach—potentially including wave-like structures—yet were analyzed via averaging and mixed-data methods to obtain robust shock parameters. Utilizing our ShOck Detection Algorithm database, the shocks are categorized into fast-forward, fast-reverse, slow-forward, and slow-reverse types. We investigate the statistical properties of these shocks, focusing on correlations between key parameters—magnetic field compression, density compression, shock normal angle, and change in velocity—and heliocentric distance. Significant positive correlations are identified between heliocentric distance and both magnetic field compression and density compression, suggesting that shocks strengthen as they propagate away from the Sun, largely due to the high local magnetosonic speeds closer to the Sun that can suppress shock formation except in extremely fast events. These findings provide new insights into the dynamic processes governing shock evolution in the inner heliosphere, including scenarios where the near-radial magnetic field geometry may lead to predominantly quasi-parallel shock configurations and thus affect near-Sun particle acceleration efficiency. We also provide strong evidence for the existence of slow-mode shocks near the Sun, contributing to the understanding of shock formation and evolution in the inner heliosphere.

Keywords: Interplanetary medium, Shocks, Solar wind
The Energy Sharing Timescale in an Analytic Framework for Common Envelope Hydrodynamics. We propose a new predictive theory for the analysis of common envelope (CE) events that incorporates the effects of relevant hydrodynamical processes into a simple analytical framework. We introduce the ejection and dynamical parameters ξ and β, which define whether envelope ejection is energetically or hydrodynamically favorable, respectively, during CE inspiral. When combined, these parameters offer a detailed narrative of how inspiral begins, proceeds, and ends that is consistent with preliminary comparisons to 3D hydrodynamical models. This physically motivated framework impacts predictions for CE outcomes, especially for systems that have energy excess, and offers promise as a potential alternative for the treatment of CEs in binary population synthesis.

Keywords: Hydrodynamical simulations, Binary stars, Multiple star evolution, Hydrodynamics, Stellar mergers, Close binary stars, Interacting binary stars, Common envelope binary stars, Common envelope evolution, Stellar evolution
Predicting the Rate of Fast Radio Bursts in Globular Clusters from Binary Black Hole Observations. The repeating fast radio burst (FRB) source in an old globular cluster (GC) in M81 proves that FRBs, which are typically associated with young magnetars, can also occur in old stellar populations. A potential explanation is super-Chandrasekhar binary white dwarf (BWD) coalescences, which may produce FRB-emitting neutron stars. GCs can also give rise to binary black hole (BBH) mergers detectable with gravitational waves, and the BWD coalescence rate from GCs is correlated with their BBH merger rate. For the first time, we combine independent observations of gravitational waves and FRBs to infer the origins of FRB sources. We use GC formation histories inferred from BBH observations to predict the rate of super-Chandrasekhar BWD coalescences originating from GCs as a function of redshift. We explore mass-loss and mass-conserved scenarios for BWD coalescences and find that the coalescence rates evolve differently across redshift in these two cases. In the mass-loss scenario, the BWD coalescence rates decrease with increasing redshift, similar to some recent measurements of the FRB rate as a function of redshift. We show that GCs could contribute ≲1% to the total FRB source formation rates in the local Universe. Our multimessenger approach also offers a novel method to better constrain the GC population using both FRB and gravitational-wave observations.

Keywords: Globular star clusters, Black holes, White dwarf stars, Radio bursts, Gravitational waves, N-body simulations
Early Results from GLASS-JWST. XXV. Electron Density in the Interstellar Medium at 0.7 ≲ z ≲ 9.3 with NIRSpec High-resolution Spectroscopy. The electron density (ne) of the interstellar medium (ISM) in star-forming galaxies is intimately linked to star formation and ionization condition. Using the high-resolution spectra obtained from the JWST Near-Infrared Spectrograph (NIRSpec) microshutter assembly (MSA) as part of the GLASS-JWST program, we have assembled the largest sample to date (34 galaxies) with individual ne measurements derived from the [O II] λλ3726, 29 and/or [S II] λλ6718, 32 doublets at 0.7 ≲ z ≲ 9.3. The gravitational lensing magnification by the foreground A2744 cluster allows us to probe ne in galaxies with stellar masses (M*) down to ≃107.5 M⊙ across the entire redshift range. Our analysis reveals that the [O II] flux ratios are marginally anticorrelated with a specific star formation rate (sSFR) within a 1σ confidence interval, whereas the [S II] flux ratios show no significant correlation with sSFR. Despite a clear correlation between sSFR and redshift within our sample, we find no apparent redshift evolution of ne at z ≃ 1–9. Our data set also includes 13 galaxies where ne can be measured from both [O II] and [S II]. Contrary to findings at lower redshifts, we observe considerable scatter in ne measurements from [O II] and [S II], indicating a complex gaseous environment with significant variations in ne in high-redshift galaxies. This work highlights the unique capability of JWST NIRSpec/MSA high-resolution spectroscopy to characterize the detailed physical properties of the ISM in individual high-redshift galaxies. *Based on observations acquired by the JWST under the ERS program ID 1324 (PI: T. Treu).

Keywords: Galaxy formation, Star formation, Galaxy evolution, Interstellar medium
Shedding Light on the Origin of the Broken Misaligned Circumtriple Disk around GW Ori. We revisit the origin of the observed misaligned rings in the circumtriple disk around GW Ori. Previous studies appeared to disagree on whether disk breaking is caused by the differential precession driven in the disk by the triple star system. In this Letter, we show that the previous studies are in agreement with each other when using the same set of parameters. But for observationally motivated parameters of a typical protoplanetary disk, the disk is unlikely to break due to interactions with the triple star system. We run three-dimensional hydrodynamical simulations of a circumtriple disk around GW Ori with different disk aspect ratios. For a disk aspect ratio typical of protoplanetary disks, H/r ≳ 0.05, the disk does not break. An alternative scenario for the gap's origin consistent with the expected disk aspect ratio involves the presence of circumtriple planets orbiting GW Ori.

Keywords: Trinary stars, Planet formation, Protoplanetary disks, Hydrodynamical simulations
Magnetic Reconnection: An Alternative Explanation of Radio Emission in Galaxy Clusters. Observations of galaxy clusters show radio emission extended over almost the system scale, necessitating mechanisms for particle acceleration. Previous models for acceleration, such as diffusive shock acceleration and that due to turbulence, can fall short in terms of efficiency. In this Letter, we propose the possibility of acceleration via magnetic reconnection. In particular, we invoke the plasmoid instability, which has been previously applied to understand particle energization in high-energy systems. Turbulence in galaxy clusters leads to fluctuation dynamos that are known to generate magnetic field structures consisting of sharp reversals. These form natural sites of reconnection. We perform particle-in-cell simulations of the plasmoid instability in collisionless and nonrelativistic plasmas. We show that the resulting electron energy spectra have power-law indices that are consistent with those inferred from observations. Our estimates show that the acceleration timescales are much smaller than the lifetime of the reconnecting magnetic structures indicating the feasibility of our model. The synchrotron radio luminosity estimate is about 1041 erg s‑1, agreeing with observations. Finally, we find that the maximum achievable Lorentz factor can go up to 105 indicating that acceleration due to magnetic reconnection is a promising avenue for understanding the origin of nonthermal emission in galaxy clusters.

Keywords: Galaxy clusters, Solar magnetic reconnection, High energy astrophysics, Intracluster medium, Cosmic rays
The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles. Solar flares stronger than X10 (S-flares, &gt;X10) are the highest-class flares that significantly impact on the Sun's evolution and space weather. Based on observations of Geostationary Orbiting Environmental Satellites at soft X-ray wavelength and the daily sunspot numbers (DSNs) since 1975, we obtained some interesting and heuristic conclusions: (1) both S-flares and the more powerful extremely strong flares (ES-flares, &gt;X14.3) mostly occur in the late phases of solar cycles (SCs) and low-latitude regions on the solar disk; (2) similar to X-class flares, the occurrence of S-flares in each SC is somewhat random, but the occurrence of ES-flares seems to be dominated by the mean DSN (Vm) and its rms deviation during the valley phase (Vd) before the cycle: the ES-flare number is strongly correlated with Vd, and the occurrence time of the first ES-flare is anticorrelated with Vd and Vm. These facts indicate that the higher the Vm and Vd, the stronger the SC, the more the ES-flares, and the earlier they occurred. We propose that the Sun may have a low-latitude active zone (LAZ), and most ES-flares are generated from the interaction between the LAZ and the newly emerging active regions. The correlations and the linear regression functions may provide an useful method to predict the occurrence of ES-flares in an upcoming SC, which derives that SC 25 will have about 2 ± 1 ES-flares after the spring of 2027.

Keywords: Solar cycle, Solar flares
Dust-extinction-curve Variation in the Translucent Interstellar Medium Is Driven by Polycyclic Aromatic Hydrocarbon Growth. The first all-sky, high-resolution, 3D map of the optical extinction curve of the Milky Way revealed an unexpected steepening of the extinction curve in the moderate-density, "translucent" interstellar medium (ISM). We argue that this trend is driven by growth of the total mass of polycyclic aromatic hydrocarbons (PAHs) through gas-phase accretion. We find a strong anticorrelation between the slope of the optical extinction curve—parameterized by R(V)—and maps of the PAH mass fraction (relative to the total dust mass)—parameterized by qPAH—derived from infrared emission. The range of observed qPAH indicates PAH growth by a factor of ∼2 between AV ≃ 1 and 3. This implies a factor-of-2 stronger 2175 Å feature, which is sufficient to lower R(V) by the observed amount. This level of PAH growth is possible given rapid accretion timescales and the depletion of carbon in the translucent ISM. Spectral observations by JWST would provide a definitive test of this proposed explanation of R(V) variation.

Keywords: Interstellar dust, Interstellar medium, Polycyclic aromatic hydrocarbons, Interstellar dust extinction
Life in the Bubble: How a Nearby Supernova Left Ephemeral Footprints on the Cosmic-Ray Spectrum and Indelible Imprints on Life. The Earth sits inside a 300 pc-wide void that was carved by a series of supernova explosions that went off tens of millions of years ago, pushing away interstellar gas and creating a bubble-like structure. The 60Fe peak deposits found in the deep-sea crust have been interpreted by the imprints left by the ejecta of supernova explosions occurring about 2–3 and 5–6 Myr ago. It is likely that the 60Fe peak at about 2–3 Myr originated from a supernova occurring in the Upper Centaurus Lupus association in Scorpius Centaurus (≈140 pc) or the Tucana-Horologium association (≈70 pc), whereas the ≈5–6 Myr peak is likely attributed to the solar system's entrance into the bubble. In this Letter, we show that the supernova source responsible for synthesizing the 60Fe peak deposits ≈2–3 Myr ago can consistently explain the cosmic-ray spectrum and the large-scale anisotropy between 100 TeV and 100 PeV. The cosmic-ray knee could then potentially be attributed entirely to a single nearby "PeVatron" source. Matching the intensity and shape of the cosmic-ray spectrum allows us to place stringent constraints on the cosmic-ray energy content from the supernova as well as on the cosmic-ray diffusion coefficient. Making use of such constraints, we provide a robust estimate of the temporal variation of terrestrial ionizing cosmic radiation levels and discuss their implications in the development of early life on Earth by plausibly influencing the mutation rate and, as such, conceivably assisting in the evolution of complex organisms.

Keywords: Ejecta, High-energy cosmic radiation, Astronomical radiation sources, Astrobiology, Superbubbles, Supernovae, Cosmic rays