Sazuna/UAT_keywords huggingface dataset:
Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation. Many coronal mass ejections (CMEs) initially propagate nonradially, and then transition to radial propagation in the corona. This directional transition is a significant process that determines a CME's space weather effects but remains poorly understood. Based on multiwavelength observations, we investigate the transition from nonradial to radial propagation in the low corona for two large-scale CMEs from the same active region on the solar limb. In the beginning, both CMEs move in a nonradial direction, beneath a system of overlying loops that are roughly parallel to the flux-rope axis. The CMEs laterally deform by bulging their upper flanks in the nonradial stage toward the higher corona, which results in the transition to a radial propagation direction approximately 25° away from the eruption site. After the directional transition, the nonradial-stage upper flank becomes the leading edge in the radial stage. Although the overlying loops do not strap the flux rope, their strong magnetic tension force constrains the radial expansion of part of the CME during the transition by acting on the flux-rope legs. A major portion of the filament is displaced to the southern part of a CME in the radial stage, which implies the complexity of observational CME features. This study presents the first observational investigation of the lateral deformation during the transition of CMEs from nonradial to radial in the low corona, and makes an essential contribution to the complete CME evolution picture.

Keywords: Space weather, Solar magnetic fields, Solar coronal mass ejections, Solar filament eruptions, Solar storm
A Three-dimensional Model for the Reversal in the Local Large-scale Interstellar Magnetic Field. We probe the three-dimensional geometry of the large-scale Galactic magnetic field within 1 kpc of the Sun using the Dominion Radio Astrophysical Observatory Global Magneto-Ionic Medium Survey (GMIMS) of the Northern Sky (DRAGONS). DRAGONS is a new full polarization survey of the northern sky from 350 to 1030 MHz covering decl. of ─20° &lt; δ &lt; 90° and a component of GMIMS. The first moment of the Faraday depth (FD) spectra produced from DRAGONS above 500 MHz reveals large-angular-scale FD structures with signs that alternate only once in the southern Galactic hemisphere and twice in the northern hemisphere, patterns shared by other Faraday rotation datasets. DRAGONS is the first survey to achieve high FD resolution while maintaining sensitivity to broad FD structures, enabling the first use of Galactic longitude─FD plots. These plots reveal Faraday-complex structures across the sky, indicating a slablike scenario in which emission and Faraday rotation are mixed. This complexity is overlaid on the same large-scale FD patterns that appear in the first moment map. We model these patterns as a magnetic reversal slicing through the disk on a diagonal and passing above the Sun in Galactic coordinates. We describe this reversal as a plane with a normal vector parallel to the line directed along (ℓ, b) = (168 .° 5, −60°) and estimate its distance to be between 0.25 and 0.55 kpc. Our results show that much of the observed Faraday sky may be dominated by the local magnetic field configuration.

Keywords: Galaxy magnetic fields, Milky Way magnetic fields, Galaxy structure, Interstellar medium, Radio astronomy, Milky Way Galaxy
Off-equatorial Electron Trajectories in Ganymede's Magnetosphere: Implications for a Bifurcated Ring Current Under Different Jovian Wind Conditions. Ganymede, Jupiter's largest moon, hosts a minimagnetosphere sustained by its intrinsic magnetic field and embedded in the sub-Alfvénic Jovian plasma flow, providing a unique natural laboratory for studying energetic particle behavior. By combining a test-particle model with three-dimensional, high-resolution magnetohydrodynamic simulations, we analyzed energetic electron drift motions under G8, G28, and G29 upstream conditions. Key findings include: First, we show that Ganymede's magnetosphere supports not only the typical equatorial trajectories of energetic electrons but also novel off-equatorial ones, as a consequence of strong Jovian wind compressions under all upstream plasma conditions. Second, equatorial and off-equatorial trajectories confine electrons to drift shells at different latitudinal regions, implying that the electron ring current may adopt a bifurcated configuration. Third, the ring current manifests short-timescale disturbances associated with intermittent magnetopause reconnections, which are modulated by a 10 hr periodicity driven by Jupiter's rotation. While in situ particle measurements remain limited, our results provide new insights into the structure and variability of Ganymede's electron ring current, awaiting confirmation by the ongoing JUICE mission.

Keywords: Planetary magnetospheres, Ganymede
The Combined X-Ray and γ-Ray Modeling of Millisecond Pulsar PSR J0030+0451 in the Dissipative Magnetospheres. Modeling of the Neutron Star Interior Composition Explorer (NICER) X-ray light curves of millisecond pulsar PSR J0030+0451 provides strong evidence for the existence of nondipole magnetic fields. We study the X-ray and γ-ray emission of PSR J0030+0451 in the dissipative dipole plus off-centred quadrupole magnetospheres. The dissipative force-free (FF) + Aristotelian electrodynamics (AE) dipole magnetospheres by combining FF and AE are solved by a 3D pseudospectral method in the rotating coordinate system. We use the FF+AE dipole plus off-centred quadrupole fields with minimum free parameters to reproduce two hotspot configurations found by the NICER observations. The X-ray and γ-ray emission from PSR J0030+0451 are simultaneously computed by using a ray-tracing method and a particle trajectory method. The modeled X-ray and γ-ray emission is then directly compared with those of PSR J0030+0451 from the NICER and Fermi observations. Our results can well reproduce the observed trends of the NICER X-ray and Fermi γ-ray emission for PSR J0030+0451.

Keywords: Magnetic fields, Gamma-rays, Pulsars
A Closed-form Analytical Theory of Nonisobaric Transmission Spectroscopy for Exoplanet Atmospheres. Analytical models are essential for building physical intuition and guiding the interpretation of exoplanet observations by clarifying the dependencies that shape atmospheric signatures. I present a generalization of the classical isothermal, isobaric transmission model by allowing the opacity to vary with pressure as a power law, κ ∝ Pn, and explicitly defining the reference opacity κ0 at a chosen pressure P0. By treating the slant optical depth as an Abel transform of the radial absorption coefficient, I derive a closed-form expression for the effective transit radius in a hydrostatic, isothermal atmosphere with pressure-dependent opacity. The solution provides a compact framework for exploring nonisobaric effects and explicitly links the vertical opacity gradient to observable spectral features. I benchmark the model against empirical transmission spectra of Earth and the hot Jupiter WASP-39b, finding a significantly improved fit relative to the isobaric formula. This generalized expression offers a physically interpretable foundation for analyzing high-precision spectra from JWST and upcoming ARIEL observations, and can serve as a basis for semianalytical retrieval approaches optimized for computational efficiency.

Keywords: Analytical mathematics, Radiative transfer, Exoplanet atmospheres, Transmission spectroscopy
Resistive Scaling in the Magnetic Helicity-driven Inverse Cascade. The inverse cascade in MHD turbulence plays a crucial role in various astrophysical processes such as galaxy cluster formation, solar and stellar dynamo mechanisms, and the evolution of primordial magnetic fields in the early Universe. A standard numerical approach involves injecting magnetic helicity at intermediate length scales to generate a secondary, time-dependent spectral peak that gradually propagates toward larger scales. Previous simulations have already suggested a resistive dependence of inverse transfer rates and demonstrated the significant influence of magnetic helicity flux density ϵH on this process. On dimensional grounds, we have for the spectral envelope  EM(k,t)≤CHϵH2/3k−1 , where CH represents a potentially universal dimensionless coefficient analogous to the Kolmogorov constant. We present a summary of the 25 distinct simulations conducted with the PENCIL CODE, systematically varying the forcing wavenumber kf, magnetic Prandtl number PrM, grid resolution N3, and Lundquist number Lu. We obtained CH and corresponding error bars by calculating the compensated spectrum and investigated its dependence with Lu and kf. For the CH─Lu relationship, we observe strong correlations with a power-law exponent around unity. In contrast, we find no significant correlation between CH and kf. We also present evidence for a nonresistive scaling of the form  EM(k,t)≤C2/3vA2k−1 , where vA is the rms Alfvén speed and C2/3 ≍ 0.4 for all of our runs.

Keywords: Magnetic fields
Very Massive Stars and High N/O: A Tale of the Nitrogen-enriched Super Star Cluster in the Sunburst Arc. The lensed Sunburst Arc (z = 2.369) hosts a young (∼2─4 Myr), massive (M⋆ ∼ 107 M⊙), compact (Reff ∼ 8 pc) Lyman-continuum leaking super star cluster, which powers a compact (&lt;10 pc), high-pressure nebula at subsolar metallicity ∼0.2 Z⊙ and with an anomalously elevated nitrogen-to-oxygen ratio  log(N/O)∼−0.2 . We present semianalytic models and 3D magnetohydrodynamic simulations in an attempt to reproduce this system. The results indicate that the progenitor giant molecular cloud (GMC) may have Mcloud ≳ 3 × 107 M⊙ and Rcloud ∼ 70 pc, corresponding to a surface density ∼103─104 M⊙ pc−2. Incorporating feedback from individual very massive stars (VMSs; ≥100 M⊙) sampled from the Kroupa initial mass function, we find that their winds rapidly enrich ∼104 M⊙ of nearby gas with nitrogen (∼1 dex) and helium (∼0.1─0.2 dex). In the first 1─3 Myr, some cold gas falls to the system center where a central cluster builds up from subcluster mergers. There, the gas is photoionized, pressurized, and chemically enriched by the newly formed VMSs, before being radiatively expelled in the next ∼1 Myr. We find that both VMS feedback and a high-surface-density progenitor GMC are necessary to reproduce the observed nebular properties, such as high N/O, high pressure, and stellar proximity. Low metallicity (Z ≤ 0.004) may be essential to avoid overproduction of carbon from WC stars. Such enrichment processes localized to compact starbursts may have caused strong nitrogen emission from dense ionized gas as observed in high-redshift galaxies such as GN-z11 and GS_3073.

Keywords: Star formation, Chemical enrichment, Massive stars, Young star clusters
Exploring NGC 7067: Comprehensive Analysis of Multiwavelength Photometric, Reddening, and Orbit Using Gaia DR3 and 2MASS. This study used Bayesian analysis alongside various statistical methods to examine the young open cluster NGC 7067, utilizing Gaia DR3 and Two Micron All Sky Survey data. We identified probable members of the cluster using density-based spatial clustering of applications with noise and used Bayesian Analysis for Stellar Evolution with nine variables software to fit the age, [Fe/H], distance and Av of the cluster. Then we used the fitting results to simulate the mass of each member star and identified binary stars and carried out mass analysis, reddening analysis, and orbit analysis. We estimate the log(Age) of the cluster to be about  7.11−0.058+0.059 , [Fe/H] to be  −0.082−0.031+0.034 , distance to be  5267.4−74.61+85.53pc , and Av to be  2.565−0.022+0.023 . The dynamical relaxation time of the cluster in log(Age) is 7.52. This makes NGC 7067 a good object for studying the causes of mass segregation and the evolution of star formation. The cluster's orbit indicates that it was born very close to the Galactic disk.

Keywords: Fundamental parameters of stars, Open star clusters, Binary stars, Star clusters
Searches for Prompt Low-frequency Radio Counterparts to Gravitational-wave Event S250206dm with the OVRO-LWA Time Machine. We report on a search for prompt, low-frequency radio emission from the gravitational-wave (GW) merger S250206dm using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). Early alerts favored a neutron-star-containing merger, making this a compelling target. Motivated by theoretical predictions of coherent radio bursts from mergers involving a neutron star, we utilized the OVRO-LWA Time Machine system to analyze voltage data recorded around the time of the event. Time Machine is a two-stage voltage buffer and processing pipeline that continuously buffers raw data from all antennas across the array's nearly full-hemisphere instantaneous field of view, enabling retrospective beamforming, dedispersion, and fast-transient candidate identification. For this event, we analyzed a 30 minute interval beginning 3.5 minutes after the merger, which included 2 minutes of pre-alert data recovered by the ring buffer. We searched the 50% localization probability region with millisecond time resolution in the 69─86 MHz frequency band. No radio counterpart was detected above a 7σ fluence detection threshold of ∼150 Jy ms. Using Bayesian analysis, we place a 95% confidence upper limit on the source luminosity of L95 = 4 × 1041 erg s−1. These constraints start to probe the bright end of the coherent-emission parameter space predicted by jet─interstellar medium shock processes, magnetar and blitzar-like mechanisms, and recent simulation-based scenarios for neutron-star-containing mergers. This study presents the first sensitive, large-area, millisecond-timescale search for prompt low-frequency radio emission from a GW merger with the OVRO-LWA, establishing a framework in which about 10 additional events will yield stringent population-level constraints.

Keywords: Neutron stars, Radio astronomy, Gravitational waves, Radio transient sources
Formation of Circumstellar Material during Double-white-dwarf Mergers and the Early Excess Emissions in Type Ia Supernovae. Early excess emission observed in Type Ia supernovae (SNe Ia) within ∼1 day of explosion provides a critical window into their progenitor systems. In the present study, we investigate formation of the circumstellar matter (CSM) in double white-dwarf (WD) mergers. We further study the interaction between the CSM and the SN ejecta. We first model the orbital evolution and super-Eddington mass transfer/ejection in the double WD systems. We then conduct hydrodynamical and light-curve (LC) simulations of the SN─CSM interaction, assuming a prompt SN Ia explosion in the context of the carbon-ignited violent merger (C-ignited VM). Our simulations show that at the moment of the merger, the binary system has the CSM distribution following  ρCSM≃D(r/1014cm)−3.5(D≃10−14─10−13gcm−3) . The simulated LCs reproduce the early flux excesses across optical to UV bands, as well as their color evolution, observed in the VM candidates, i.e., 03fg/02es-like SNe Ia. This supports that 03fg/02es-like objects originate from the VM explosions. We also discuss the case of the helium-ignited VM, which might be realized in some WD─WD mergers depending on the He content in the system. Focused here is the timing when the explosion is initiated, and we find that the explosion is initiated after the companion WD is, at least partially, tidally disrupted also in this case; we thus expect the formation of the CSM through the mass transfer phase also for the helium-ignited VM scenario.

Keywords: Circumstellar matter, White dwarf stars, Type Ia supernovae
Energetic Nonthermal Electrons within the Above-the-looptop Regions in Solar Flares: Acceleration, Feedback, and Quasiperiodic Pulsations. Solar flares are among the most dramatic events in the solar system, releasing substantial magnetic energy and accelerating a large number of electrons to high energies. Notably, in certain events, the above-the-looptop region may contain a significant population of nonthermal electrons, both in number and energy. For the first time, we adopt a novel numerical method that combines magnetohydrodynamics with energetic particles incorporating feedback from nonthermal electrons to investigate electron acceleration and transport in solar flares. We find that a large fraction of energetic electrons are accelerated via the current sheet and termination shock regions. Most energetic electrons are concentrated in the above-the-looptop region, carrying a sizable amount of the released energy. We observe that greater feedback of nonthermal electrons leads to steeper energy spectra. The energy density of the nonthermal electrons oscillates due to the periodic impact of magnetic islands into the above-the-looptop region, which may help explain the observed quasiperiodic pulsations. Our simulations provide new insights into the origin of nonthermal electrons and associated emissions in the above-the-looptop region.

Keywords: Solar flares
3D Macro Physics and Light Odd-Z Element Production in O-C Shell Mergers: Implications for <SUP>40</SUP>K Production and Radiogenic Heating Inventories of Rocky Exoplanets. The light odd-Z elements P, Cl, K, and Sc are underproduced in galactic chemical evolution models compared to spectroscopic observations of stars in the Milky Way. The most promising solution to this puzzle is that some massive stars experience O-C shell mergers, boosting their yields through dynamic, convective-reactive nucleosynthesis. We report how convective macro physics based on 3D 4π hydrodynamic simulations impacts production in the O shell by postprocessing the MZAMS = 15 M⊙ Z = 0.02 model from the NuGrid dataset. We explore a mixing downturn, boosted velocities, reduced ingestion rate, and convective quenching. Across 24 mixing cases, the pre-explosive yields for [P/Fe], [Cl/Fe], [K/Fe], and [Sc/Fe] are modified by [−0.33, 0.23], [−0.84, 0.64], [−0.78, 1.48], and [−0.36, 1.29] dex, respectively. Cases with a convective downturn with the fastest ingestion rate have the largest enhancement, and production is nonmonotonic with boosted velocities. Which reactions are most important for the convective-reactive element production pathways depends on the mixing case. We parameterize production of 40K (t1/2 = 1.248 Gyr), an important radiogenic heat source for younger (2─3 Gyr) rocky planets, and find a yield variation exceeding 3 orders of magnitude. This range of initial abundances for 40K implies the early geodynamic behavior of silicate mantles in rocky planets can differ greatly from that of Earth. These results underscore the importance of investigating the 3D macro physics of shell merger convection through hydrodynamic simulations to develop a predictive understanding of the origin and variability of the light odd-Z elements and the 40K/K ratio in planet host stars.

Keywords: Exoplanets, Massive stars, Nuclear astrophysics, Stellar convective shells, Oxygen burning, Habitable planets
Two-stage Primary Acceleration in Filament Initial Eruption under a Fan─Spine Magnetic Configuration. Understanding the filament rising process is crucial for unveiling the triggering mechanisms of coronal mass ejections and forecasting space weather. In this paper, we present a detailed study of the filament initial eruption under a fan─spine structure. It was found that the filament underwent two distinct acceleration stages corresponding to class M1.0 and M4.6 flare events. The first acceleration stage commenced with the filament splitting, after which the upper portion was subsequently heated, being a hot channel, and slowly rose at an average speed of 22 km s−1. A set of hot reverse C-shaped loops appeared repeatedly during the filament splitting, and a hook structure was recognized at this phase, suggesting ongoing growth of the magnetic flux rope (MFR). When it reached a certain altitude, the hot channel appeared to get into a quasi-static phase with its upper edge seriously decelerated and its lower edge expanding downward. Approximately 30 minutes later, as a distinct annular ribbon appeared outside the hook structure, the hot channel rose again at a velocity of over 50 km s−1 accompanied by rapidly drifting footpoints and experienced a second acceleration stage with its axial flux increased to 1.1 × 1021 Mx. It is deduced that the filament initial eruption under a magnetic dome possesses multiple kinetic processes. We suggest that the magnetic reconnection taking place within and beneath the filament continues to trigger the growth of preeruptive MFR and the first acceleration, when the magnetic reconnection above the filament plays a key role in the second acceleration.

Keywords: Solar magnetic fields, Solar flares, Solar filaments, Solar filament eruptions
Lomb─Scargle Periodogram Struggles with Non-sinusoidal Supermassive Black Hole Binary Signatures in Quasar Lightcurves. Supermassive black hole binary (SMBHB) systems are expected to form as a consequence of galaxy mergers. At subparsec separations, SMBHBs can be identified as quasars with periodic variability, with previous periodicity searches uncovering significant candidates. However, these searches focused primarily on sinusoidal signals, while theoretical models and hydrodynamical simulations predict that binaries produce more complex non-sinusoidal pulse shapes. Here we examine the efficacy of the Lomb─Scargle periodogram (LSP; one of the most popular tools for periodicity searches in unevenly sampled lightcurves) to detect periodicities with a sawtooth shape mimicking results of hydrodynamical simulations. We simulate idealized well-sampled lightcurves, lightcurves that mimic the data in the Palomar Transient Factory (PTF) analyzed in M. Charisi et al. (2016), and lightcurves that resemble our expectations for single-band data in the upcoming Legacy Survey of Space and Time (LSST) of the Rubin Observatory. We approximate quasar variability with a damped random walk (DRW) model, inject sinusoidal and sawtooth pulse shapes, and assess their statistical significance. We find that in the presence of red noise, the LSP detects a relatively low fraction of the sinusoidal signals (∼45%, ∼24%, and ∼23%, in the PTF-like, idealized, and LSST-like lightcurves, respectively). The fraction is significantly reduced for sawtooth periodicity (with only ∼9% in PTF-like and ∼1% in idealized and LSST-like lightcurves). These low recovery rates imply that previous searches have missed the large majority of binaries. They also have significant implications for the detection of SMBHBs in upcoming LSST necessitating the development of advanced tools that go beyond the simple LSP.

Keywords: Quasars