Sazuna/UAT_keywords huggingface dataset:
Steady-state Heating of Diffuse Coronal Plasma in a Solar Active Region. The solar corona is much hotter than lower layers of the solar atmosphere—the photosphere and chromosphere. The coronal temperature is up to 1 MK in quiet Sun areas, while up to several megakelvins in active regions, which implies a key role of the magnetic field in coronal heating. This means that understanding coronal heating requires reliable modeling of the underlying 3D magnetic structure of an active region validated by observations. Here, we employ synergy between 3D modeling, optically thick gyroresonant microwave emission, and optically thin EUV emission to (i) obtain and validate the best magnetothermal model of the active region and (ii) disentangle various components of the EUV emission known as diffuse component, bright loops, open-field regions, and "moss" component produced at the transition region. Surprisingly, the best thermal model corresponds to high-frequency energy release episodes, similar to a steady-state heating. Our analysis did not reveal significant deviations of the elemental abundances from the standard coronal values.

Keywords: Solar coronal radio emission, Solar active region magnetic fields, Astronomy data modeling, Solar coronal heating, Solar active regions, Solar corona, Solar activity
Saturns, but Not Super-Jupiters, Occur More Frequently in the Presence of Inner Super-Earths. Studies from recent years have reached different conclusions regarding how frequently super-Earths are accompanied by long-period giant planets and vice versa. This relation has been predicted to be mass dependent by planet-formation models. We investigate that as the origin of the discrepancy using a radial velocity sample: the California Legacy Survey. We perform detection completeness corrections in order to discard detection bias as a possible explanation to our results. After bias corrections, we find that cold Jupiters are  5.65‑2.57+1.08  times more massive when not in the company of an inner super-Earth, while super-Earths are not significantly more massive while in the company of an outer giant planet. We also report an occurrence enhancement for Saturns (median projected mass of 0.6MJ) while in presence of a super-Earth by a factor of ∼4, and for super-Earths in the presence of Saturns by the same factor. This positive correlation disappears for super-Jupiters (median projected mass of 3.1MJ). These results show that while cold Jupiters are generally accompanied by inner super-Earths, this does not hold for the largest giant planets, such as those that will be discovered by Gaia, which will likely not be accompanied by transiting planets. The mass dependence, in combination with the different detection limits of different surveys, may explain the discrepancies concerning occurrence relations between cold Jupiters and super-Earths.

Keywords: Exoplanet astronomy, Exoplanet systems, Exoplanets
On Convective Turnover Times and Dynamos in Low-mass Stars. The relationship between magnetic activity and Rossby number is one way through which stellar dynamos can be understood. Using measured rotation rates and X-ray to bolometric luminosity ratios of an ensemble of stars, we derive empirical convective turnover times based on recent observations and reevaluate the X-ray activity–Rossby number relationship. In doing so, we find a sharp rise in the convective turnover time for stars in the mass range of 0.35‑0.4 M⊙, associated with the onset of a fully convective internal stellar structure. Using MESA stellar evolution models, we infer the location of dynamo action implied by the empirical convective turnover time. The empirical convective turnover time is found to be indicative of dynamo action deep within the convective envelope in stars with masses 0.1–1.2 M⊙, crossing the fully convective boundary. Our results corroborate past works suggesting that partially and fully convective stars follow the same activity–Rossby relation, possibly owing to similar dynamo mechanisms. Our stellar models also give insight into the dynamo mechanism. We find that empirically determined convective turnover times correlate with properties of the deep stellar interior. These findings are in agreement with global dynamo models that see a reservoir of magnetic flux accumulates deep in the convection zone before buoyantly rising to the surface.

Keywords: Stellar convection envelopes, Stellar evolutionary models, Stellar magnetic fields, Stellar activity, Stellar rotation
Lyα Radiative Transfer Modeling for 163 MUSE Lyα-emitting Galaxies at z = 3─6. We utilized Lyα radiative transfer calculations from H. Song et al. to investigate the properties of extended Lyα halos around star-forming galaxies in the Hubble Ultra Deep Field, observed by the Multi-Unit Spectroscopic Explorer. Expanding on the work of H. Song et al., which was limited to eight galaxies, we derived best-fit models for a significantly larger sample of 163 galaxies, which successfully reproduced both their Lyα spectra and surface brightness profiles (SBPs). These best-fit models suggest a broad medium distribution surrounding each galaxy, with low expanding velocities at large radii. This conclusion could not have been drawn from modeling either the spectrum or SBP alone, but only through simultaneous modeling of both. Our correlation analysis between observables and model parameters reveals that the spatial extent of Lyα halos is primarily determined by the extents of the medium and the source, while the spectral peak shift and full width at half maximum are governed mainly by optical depth, with the velocity structure of the medium playing a secondary yet nonnegligible role. The fact that various correlations derived from the full set of models and those from the best-fit subset can differ significantly highlights the complex and interdependent nature of Lyα radiative transfer. All model parameters interact to shape the observed Lyα features in a nontrivial way.

Keywords: Lyman-alpha galaxies, Radiative transfer simulations
Searching for Axion Dark Matter Gegenschein of the Vela Supernova Remnant with FAST. Axions are one of the leading dark matter candidates. If we are embedded in a Milky Way dark matter halo comprised of axions, their stimulated decay would enable us to observe a counterimage ("axion gegenschein") with a frequency equal to half the axion mass in the opposite direction of a bright radio source. This spectral line emission will be broadened to Δν/ν ∼ σd/c ∼ 10‑3 due to the velocity dispersion of dark matter, σd. In this pilot study, we perform the first search for the expected axion gegenschein image of Vela supernova remnant with 26.4 hr of effective ON–OFF data from the Five-hundred-meter Aperture Spherical radio Telescope (FAST) L-band (1.0–1.5 GHz) 19 beam receiver. Our null detection limits the axion–photon coupling strength to be gaγγ ≲ 2 × 10‑10 GeV‑1 in the mass ranges of 8.7 μeV ≤ ma ≤ 9.44 μeV and 10.85 μeV ≤ ma ≤ 12.01 μeV. These results provide a stronger constraint on gaγγ in this axion mass range than the current limits obtained by the direct search of an axion decay signal from a dwarf galaxy that uses FAST observations, but are a factor of ∼3 times weaker than the current CERN Axion Solar Telescope limit. Based on our observation strategy, data processing methods, and results, the expected sensitivity will reach ∼10‑11 GeV‑1 with ∼2000 hr of observation in the future.

Keywords: Dark matter
Investigating the Anticorrelation between Photon Index and Flux of the Crab Using RXTE and NuSTAR. We present a systematic study of the recently reported anticorrelation between X-ray flux and photon index (Γ) in the Crab Nebula, using archival Rossi X-Ray Timing Explorer (RXTE) Proportional Counter Array (3–50 keV), RXTE High Energy X-ray Timing Experiment (HEXTE; 20–100 keV), and Nuclear Spectroscopic Telescope Array (3–78 keV) observations. Spectra were extracted in soft (3–10 keV) and hard bands (10–50, 10–78, 20–100 keV) and fitted with an absorbed power-law model. Across all instruments and energy ranges, we confirm the existence of a persistent negative correlation–harder spectra at higher flux levels. The correlation is stronger in the hard bands compared to the soft bands. This is consistent with synchrotron emission modulated by magnetic-field variations in the pulsar wind nebula.

Keywords: X-ray astronomy, Pulsar wind nebulae
Grand Design Spiral Arms in the Compact, Embedded Protoplanetary Disk of Haro 6-13. Millimeter continuum spiral arms have so far only been detected in a handful of protoplanetary disks, and thus we have a limited understanding of the circumstances in which they can form. In particular, substructures in small disks (R ⪅ 50 au) have not been well characterized in comparison with large disks. We present Atacama Large Millimeter/submillimeter Array 1.3 mm continuum observations of the disk around the T Tauri star Haro 6-13 at a resolution of  ∼0.″04  (∼5 au). A pair of low-contrast spiral arms are detected at disk radii from ∼10 to 35 au. They can be approximated as Archimedean spirals with pitch angles ranging from ∼10° to 30°. The low value of the disk-averaged spectral index between 1.3 and 3 mm (α = 2.1) and the high brightness temperatures suggest that the millimeter continuum is likely optically thick and thus may hide sufficient mass for the disk to become gravitationally unstable and form spiral arms. CO observations have shown that Haro 6-13 is surrounded by an envelope, raising the possibility that infall is facilitating spiral arm formation.

Keywords: Millimeter astronomy, Protoplanetary disks, Planet formation
Modeling YSO Jets in 3D I: Highly Variable Asymmetric Magnetic Pressure-Driven Jets in the Polar Cavity from Toroidal Fields Generated by Inner Disk Accretion. Jets and outflows are commonly observed in young stellar objects, yet their origins remain debated. Using 3D nonideal magnetohydrodynamic (MHD) simulations of a circumstellar disk threaded by a large-scale open poloidal magnetic field, we identify three components in the disk-driven outflow: (1) a fast, collimated jet, (2) a less collimated, slower laminar disk wind, and (3) a magneto-rotational instability (MRI)-active turbulent disk wind that separates the former two. At high altitudes, the MRI-active wind merges with the laminar disk wind, leaving only the jet and disk wind as distinct components. The jet is powered by a novel mechanism in the star formation context: a lightly mass-loaded outflow driven by toroidal magnetic pressure in the low-density polar funnel near the system's rotation axis. A geometric analysis of the magnetic field structure confirms that magnetic tension does not contribute to the outflow acceleration, with magnetic pressure acting as the dominant driver. While the outflow in our model shares similarities with the magneto-centrifugal model—such as angular momentum extraction from the accreting disk—centrifugal forces play a negligible role in jet acceleration. In particular, the flow near the jet base does not satisfy the conditions for magneto-centrifugal wind launching. Additionally, the jet in our simulation exhibits strong spatial and temporal variability. These differences challenge the applicability of rotation─outflow velocity relations derived from steady-state, axisymmetric magneto-centrifugal jet models for estimating the jet's launching radius. For the slower disk wind, vertical motion is driven by toroidal magnetic pressure, while centrifugal forces widen the wind's opening angle.

Keywords: Accretion, Jets, Young stellar objects, Circumstellar disks, Magnetic fields, Magnetohydrodynamical simulations
Mother's Day Superstorms: Pre- and Post-storm Evolutionary Patterns of ARs 13664/8. In the week including Mother's Day 2024, active region (AR) 13664 became superactive when AR 13668 emerged nearby, causing multiple X-class flares and coronal mass ejections, and an increase in activity level similar to that inferred from geomagnetic storms associated with the historic 1859 events. By analyzing both global warped toroids on which the active regions are strung, and active-region-scale magnetic flux and helicity, we find (i) the north and south toroids have nearly identical warped patterns, with mostly longitudinal wave numbers m = 1–3; (ii) in three longitude intervals the north and south toroids were tipped away from each other in latitude, with a longitude phase shift between them, creating locations most prone to AR eruptions; (iii) on an active region scale, vector magnetic fields deviate far from potential fields, and therefore contain large amounts of magnetic "free energy" available for conversion into kinetic energy and high-temperature radiation; (iv) the positive and negative polarities converge toward each other, facilitating reconnection and magnetic energy release; and (v) rapid changes in magnetic helicity, caused by helicity injection from below that creates helicity imbalances. Despite the coarser resolution of GONG magnetograms, the derived global toroids are strikingly similar to those derived from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager. We conclude that the Mother's Day superstorms were caused by enhanced magnetic complexity occurring due to intricate interactions among multiple active regions emerging at nearly the same locations. This suggests that predicting the locations of magnetically complex active regions, and studying and tracking their eruptive states using different proxy parameters can greatly improve our ability to forecast intense storms, not only hours but potentially weeks in advance.

Keywords: Solar activity, Solar active regions, Solar flares
Comprehensive Radio Monitoring of the Black Hole X-Ray Binary Swift J1727.8‑1613 during Its 2023–2024 Outburst. This work presents comprehensive multifrequency radio monitoring of the black hole low-mass X-ray binary (LMXB) Swift J1727.8‑1613, which underwent its first recorded outburst after its discovery in 2023 August. Through a considerable community effort, we have coalesced the data from multiple, distinct observing programs; the light curves include ∼10 months and 197 epochs of monitoring from seven radio facilities with observing frequencies ranging from (approximately) 0.3–230 GHz. The primary purpose of this work is to provide the broader astronomical community with these light curves to assist with the interpretation of other observing campaigns, particularly nonradio observing frequencies. We discuss the phenomenological evolution of the source, which included (i) multiple radio flares consistent with the launching of discrete jet ejections, the brightest of which reached ∼1 Jy; (ii) temporally evolving radio spectral indices (α), reaching values steeper than expected for optically thin synchrotron emission (α &lt; ‑1) and emission with significant radiative cooling (α &lt; ‑1.5). We have published a digital copy of the data and intend for this work to set a precedent for the community to continue releasing comprehensive radio light curves of future LMXB outbursts.

Keywords: Accretion, X-ray binary stars, Black holes, Relativistic jets, Radio continuum emission
The Emerging Black Hole Mass Function in the High-redshift Universe. Observations with the James Webb Space Telescope (JWST) have identified an abundant population of supermassive black holes (SMBHs) already in place during the first few hundred million years of cosmic history. Most of them appear overmassive relative to the stellar mass in their host systems, challenging models of early black hole seeding and growth. Multiple pathways exist to explain their formation, including heavy seeds formed from direct collapse/supermassive stars or sustained super-Eddington accretion onto light stellar remnant seeds. We use the semianalytical code Ancient Stars and Local Observables by Tracing Halos to predict the emerging SMBH mass function under physically motivated models for both light- and heavy-seed formation, to be compared with upcoming ultradeep JWST surveys. We find that both pathways can reproduce observations at z ∼ 5–6, but have distinct features at higher redshifts of z ∼ 10. Specifically, JWST observations have the potential to constrain the fraction of efficiently accreting (super-Eddington) SMBHs, as well as the existence and prevalence of heavy seeds, in particular through ultradeep observations of blank fields and/or gravitational lensing surveys. Such observations will provide key insights to understand the process of SMBH formation and evolution during the emergence of the first galaxies. We further emphasize the great promise of possible SMBH detections at z ≳ 15 with future JWST observations to break the degeneracy between light- and heavy-seed models.

Keywords: Early universe, Galaxy formation, Supermassive black holes, Theoretical models, Active galactic nuclei
The Detection of Spatially Resolved Protostellar Outflows and Episodic Jets in the Outer Galaxy. We present the first detection of spatially resolved protostellar outflows and jets in the outer Galaxy. We observed five star-forming regions in the outer Galaxy (Sh 2-283 and NOMF05-16/19/23/63; galactocentric distance = 15.7–17.4 kpc) with the Atacama Large Millimeter/submillimeter Array. Toward Sh 2-283, we have detected distinct outflow (∼5–50 km s‑1) and jet components (∼50–100 km s‑1) associated with the protostar in CO(3–2) emission. The outflows and jets are well collimated, with the jets exhibiting multiple bullet structures. The position–velocity diagram along the CO flow axis shows two characteristic structures: (a) the flow velocity, which linearly increases with the position offset from the core center (the Hubble-like flow); and (b) the continuous velocity components of the periodical flows (spine-like structures), which may indicate episodic mass ejection events. The time intervals of the mass ejection events are estimated to be 900–4000 yr, based on the slopes of these spine-like structures. These characteristics align with those of nearby protostellar systems, indicating that early star formation in low-metallicity environments, such as the outer Galaxy, resembles that in the inner Galaxy. In contrast to the physical similarities, the N(SiO)/N(CO) ratio in the jet bullet appears to be lower than that measured in the low-mass protostellar sources in the inner Galaxy. This may indicate a different shock chemistry or different dust composition in the outer Galaxy source, although non–local thermodynamic equilibrium effects could also affect the observed low N(SiO)/N(CO) ratio. We also report the new detection of four other outflow sources in the outer Galaxy.

Keywords: Interstellar molecules, Stellar jets, Chemical abundances, Stellar winds, Protostars, Metallicity
A Comprehensive Light-curve Model of the Very Fast Nova V1674 Herculis. V1674 Her is one of the fastest novae, of which the very early phase is well observed, including optical rise to the peak over 10 mag. We present a full theoretical light-curve model of V1674 Her. Our 1.35 M⊙ white dwarf (WD) model with the mass accretion rate of 1 × 10‑11 M⊙ yr‑1 explains overall properties including a very fast rise and decay of the optical V light curve. The WD photosphere expands up to 21 R⊙, thus a 0.26 M⊙ companion star orbiting the WD every 3.67 hr is engulfed 2.7 hr after the onset of thermonuclear runaway and appears 5.3 days after that. The duration of X-ray flash is only 0.96 hr. The evolution of the expanding envelope and temporal change of the photospheric radius are very consistent with observed optical and X-ray modulations with the orbital and spin (501 s) periods. We confirm that the decay phase of the nova light curve is well approximated by a sequence of steady-state envelope solutions. Using the time-stretching method of nova light curves, we obtain the V-band distance modulus of (m ‑ M)V = 16.3 ± 0.2 and determine the distance to be d = 8.9 ± 1 kpc for the interstellar extinction of E(B – V) = 0.5 ± 0.05.

Keywords: Stellar winds, X-ray binary stars, Classical novae
Precise Age for the Binary HD 21278 in the Young α Persei Cluster. We present a study of the double-lined spectroscopic binary HD 21278 that contains one of the brightest main-sequence stars in the young α Persei open cluster. We analyzed new spectra and reanalyzed archived spectra to measure precise new radial velocity curves for the binary. We also obtained interferometric data using the CHARA Array at Mount Wilson to measure the sky positions of the two stars and the inclination of the ∼2 mas orbit. We determine that the two stars have masses of 5.381 ± 0.084 M⊙ and 3.353 ± 0.064 M⊙. From isochrone fits, we find the cluster's age to be 49 ± 7 Myr (using PARSEC models) or 49.5 ± 6 Myr (MIST models). Finally, we revisit the massive white dwarfs that are candidate escapees from the α Persei cluster to try to better characterize the massive end of the white dwarf initial–final mass relation. The implied progenitor masses challenge the idea that Chandrasekhar-mass white dwarfs are made by single stars with masses near 8 M⊙.

Keywords: White dwarf stars, Spectroscopic binary stars, Long baseline interferometry, Photometry, Open star clusters, Stellar evolution
SPINN: Advancing Cosmological Simulations of Fuzzy Dark Matter with Physics Informed Neural Networks. Physics-informed neural networks (PINNs) have emerged as a powerful tool for solving differential equations by integrating physical laws into the learning process. This work leverages PINNs to simulate gravitational collapse, a critical phenomenon in astrophysics and cosmology. We introduce the Schrödinger–Poisson (SP) informed neural network which solves the nonlinear SP equations to simulate the gravitational collapse of fuzzy dark matter (FDM) in both 1D and 3D settings. The results demonstrate accurate predictions of key metrics such as mass conservation, density profiles, and structure suppression, validating against known analytical or numerical benchmarks. This work highlights the potential of PINNs for efficient, possibly scalable modeling of FDM and other astrophysical systems, overcoming the challenges faced by traditional numerical solvers due to the nonlinearity of the involved equations and the necessity to resolve multiscale phenomena, especially resolving the fine wave features of FDM on cosmological scales.

Keywords: Cosmology, Dark matter, Neural networks
Detection of Multiple X-Ray Quasi-periodic Oscillations in IGR J19294+1816 with Insight-HXMT. We report the timing results with Insight-HXMT observations of X-ray binary IGR J19294+1816 during its 2019 type I outburst at the decline phase shortly following its peak. We analyze the light curves and power density spectrum of the 2019 observations and reveal a peak at νNS ∼ 80.2 mHz, corresponding to X-ray pulsations from the neutron star. In addition, a significant quasi-periodic oscillation (QPO) feature is observed at νQPO ∼ 30.2 mHz from 10 to 50 keV, with the rms amplitude increasing with energy. Furthermore, we detect two QPOs at frequencies of ∼51.1 and 113.7 mHz (corresponding to sidebands near νNS ± νQPO) in the range 25–50 keV, exhibiting an rms amplitude of around 12%. Wavelet analysis also shows multiple QPOs at the frequencies of ∼30 mHz, 50 and 110 mHz, which have transient behaviors. The centroid frequencies of ∼30 mHz remain nearly constant for different luminosities. Our research identifies IGR J19294+1816 as the second strong magnetic field pulsar with significant sideband signals around the spin frequency. We explore various physical origins that could explain the presence of multiple QPOs.

Keywords: Neutron stars, X-ray binary stars, High mass x-ray binary stars