Sazuna/UAT_keywords huggingface dataset:
A Theoretical Study of Carbon Nanotube Formation: Carriers of the Diffuse Interstellar Bands?. Density functional theory (DFT) calculations have been conducted to probe the formation of carbon nanotubes (CNTs) from graphitic sheets in the presence of a simulated circumstellar shock wave. The sheets serve as a model for graphite layers formed on surfaces of SiC grains, as produced in experiments. The computations show that when the top graphite layer is displaced toward a lower layer under the mechanical stress of a shock, the sheets bond and curl into a CNT. The bonding between sheets always occurs along the zigzag edges, exclusively producing the "armchair" CNT or (n, m) conformer, where n = m, as opposed to the "zigzag" or "chiral" forms (n ≠ m). Multilayered graphite sheets showed the same behavior when the top sheet was mechanically perturbed, also leading to formation of energy-minimum armchair CNT structures. The optical-transition energies from the ground to first excited state for a series of armchair CNTs, E11, were calculated. Within uncertainties associated with DFT calculations, the wavelengths of the E11 transitions of the (5, 5), (8, 8), (9, 9), (10, 10), and (12, 12) CNTs match the pattern of five of the six strongest diffuse interstellar bands (DIBs), including those at 4430, 5780, and 6284 Å. These DIBs are also found in the planetary nebulae Tc-1 and M1-20, where C60 and C70 have been identified. These data further support the hypothesis that CNTs, as well as fullerenes, are formed in shocked circumstellar gas from the destruction of SiC grains and are transported into the diffuse interstellar medium.

Keywords: Circumstellar envelopes, Diffuse interstellar bands, Electronic spectroscopy, Astrochemistry, Computational methods, Interstellar dust processes
Electrons in the Collisionally Young Solar Wind: Parker Solar Probe Observations. We report new observations by the Parker Solar Probe of unique electron velocity distribution functions (VDFs) in low-density solar wind streams at heliocentric distances of ∼10─20R⊙. These VDFs have a significant core anisotropy and lack a clear energy spectral break point between the thermal core and suprathermal strahl populations, with a parallel cut through the anti-sunward distribution closely following a single-temperature Maxwellian function over up to ∼6 decades in distribution function. These characteristics correlate strongly with low collisional age parameters and high Knudsen numbers, and also to some degree with higher local and asymptotic bulk solar wind flow speeds and lower strahl temperatures. The observed VDFs may represent a unique characteristic of low-density solar wind streams, or alternatively they could represent a common occurrence in any sufficiently collisionally young stream. In either case, these observations have implications both for the detailed evolution of the electron VDF and the large-scale structure and acceleration of the solar wind.

Keywords: Space plasmas, Solar wind, Plasma physics
A Statistical Study of the Gamma-Ray Burst and Supernova Association. The association between long gamma-ray bursts (LGRBs) and core-collapse supernovae (SNe) has been well established since the discovery of SN 1998bw, which was linked to the low-luminosity LGRB 980425. However, long-term monitoring of several well-localized, low-redshift LGRBs has yielded compelling evidence for the absence of accompanying SNe. Notably, two long bursts, GRB 211211A and GRB 230307A, show signatures consistent with kilonova emission from compact binary mergers, indicating that at least some long events may originate from progenitors other than core-collapse SNe. In this study, we conduct a comparative analysis of two samples of LGRBs, i.e., LGRBs with and without SN associations, to investigate the differences that may reveal intrinsic distinctions in their progenitors. A detailed examination of their prompt emission properties, host galaxy environments, and event rates is performed. While the two samples exhibit considerable overlap in most observed properties, a significant discrepancy in their event rate is revealed. LGRBs without SN association have an event rate that aligns well with the star formation rate, whereas that of SN-associated LGRBs differs significantly. It indicates that LGRBs without an SN association may constitute a distinct subclass with intrinsically different progenitors.

Keywords: Gamma-ray bursts, Astronomy data analysis, Core-collapse supernovae, Astrostatistics
Interactions between Solar Filaments and Coronal Loops in Active Region 13229. We present a multiwavelength observational investigation of filaments and coronal loop interactions in active region NOAA 13229 during 2023 February 21─23. Our findings demonstrate that a series of interactions between filaments (F1 and F2), coronal loops, and the loop─filament system, mediated by reconnection with overlying hot coronal loops, led to the formation of a longer inverse S-shaped filament. Key mechanisms, including flux convergence, cancellation, and submergence along the polarity inversion line, drive these interactions. Photospheric horizontal plasma flows and the transverse component of the Lorentz force may facilitate footpoint convergence, enabling magnetic reconnection and structural reorganization. The nonlinear force-free field extrapolations indicate that magnetic reconnections likely occur at the interface of loop─loop or filament─loop that drive the formation of large-scale filament systems.

Keywords: Solar activity, Solar magnetic reconnection, Solar active region filaments
Magnetorotational Instability in a Solar Near-surface Mean-field Dynamo. We address the question whether the magnetorotational instability (MRI) can operate in the near-surface shear layer (NSSL) of the Sun and how it affects the interaction with the dynamo process. Using hydromagnetic mean-field simulations of αΩ-type dynamos in rotating shearing-periodic boxes, we show that for negative shear the MRI can operate above a certain critical shear parameter. This parameter scales inversely with the equipartition magnetic field strength above which α quenching set in. Like the usual Ω effect, the MRI produces toroidal magnetic field when the field is sufficiently strong. The work done by the Lorentz force is positive, so the magnetic field drives kinetic energy and not the other way around, as in a turbulent dynamo. This results in strong kinetic energy production and dissipation, which occurs at the expense of the magnetic energy. In view of the application to the solar NSSL, we conclude that the turbulent magnetic diffusivity may be too large for the MRI to be excited and that therefore only the standard Ω effect is expected to operate.

Keywords: Magnetic fields
The First Search for Optical Transient as a Counterpart of a Month-timescale IceCube Neutrino Multiplet Event. Optical transients with timescales of months, such as supernovae (SNe) and tidal disruption events (TDEs), are candidates for high-energy neutrino sources. Multiple neutrino detections from the same direction within a month timescale provide a unique opportunity to identify such optical counterparts in the nearby Universe. In this work, we conduct an archival search for the optical counterpart of an IceCube triplet event using the data of Zwicky Transient Facility. We develop a dedicated alert filtering system and validate the performance by following a blind analysis method. Applying this filtering system to the data after the detections of the IceCube triplet event, we find no transient candidates within the localization area. Assuming that the IceCube triplet event originates from an astrophysical source, we constrain parameters of the optical transient, a peak luminosity, and a decay timescale, using a simple signal model that is motivated by TDEs and superluminous SNe (SLSNe). For the case with no time lag between neutrino detections and optical peak, almost the entire parameter space of the known TDEs and SLSNe would be constrained. To give constraints on transients with a rapidly evolving light curve, quick follow-up observations for future neutrino multiplet events are crucial.

Keywords: Optical astronomy, Neutrino astronomy, Transient sources
Unveil a Peculiar Light-curve Pattern of Magnetar Burst with GECAM Observations of SGR J1935+2154. A magnetar X-ray burst (MXB) is usually composed of a single pulse or multiple pulses with rapid rise and brief duration mostly observed in the hard X-ray (soft gamma-ray) band. Previous work studied the temporal behavior of some magnetar bursts and employed the fast rise exponential decay (FRED) model to fit pulses of MXB. However, whether there is another kind of pulse shape has not been explored. In this study, we systematically examined the light curve of MXBs from SGR J1935+2154 detected by the Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor between 2021 and 2022. We find that there are different light-curve morphologies. Especially, we discover a peculiar and new pattern, exponential rise and cutoff decay (ERCOD), which is significantly different from FRED and could be well described by a mathematical function we proposed. We find that MXBs with ERCOD shape are generally longer in duration, brighter in the peak flux, and harder in spectrum than those with FRED. We note that the ERCOD shape is not unique to SGR J1935+2154 but also present in other magnetars. This new light-curve pattern may imply a special burst and radiation mechanism of magnetar.

Keywords: Neutron stars, Magnetars, Soft gamma-ray repeaters
Forming the Noncarbonaceous Chondrite Parent Bodies in the Presence of the Jupiter Barrier. Meteorites can be divided into two groups—noncarbonaceous chondrite like (NC) and carbonaceous chondrite like (CC)—with distinct stable-isotope compositions. Parent bodies of NC and CC meteorites have overlapping formation ages. This suggests they formed in different regions of the solar nebula, separated by a dynamical barrier that prevented small solids (pebbles) from mixing. NC chondrites would have formed 1─2 Myr after the barrier appeared. Pebbles in the NC region moved inwards due to radial drift and the inward flow of gas. Outward turbulent diffusion partly offset inward advection, but pebble lifetimes were finite. Survival of enough pebbles to form the NC chondrites requires that the gas flow was mainly confined to the surface layers of the solar nebula, and that pebbles remained near the midplane. This sets an upper limit on the strength of turbulence. If pebble size was set by mutual collision speeds, then turbulence strength has a lower limit as well, set by the maximum acceptable drift rate. For a barrier at 5 au from the Sun, the turbulence parameter α should lie between 2 × 10−5 and 10−3. The maximum collision speed  vmax  should not exceed 0.8 m s−1. If the pebble radius remained fixed, it should not exceed 2 mm, which is a few times larger than the mass peak seen in NC chondrules.

Keywords: Solar nebulae, Meteorite composition, Planet formation, Planetesimals
Supra-arcade Downflows in an Extensive Fan Associated with a Giant Quiescent Solar Filament Eruption. We investigate the aftermath of a giant quiescent solar filament eruption on 2023 December 24. One feature of the eruption is an extensive fan above the filament channel that is about 3 times as wide as similar structures that appear above active regions (ARs) during solar flares. The fan contains numerous supra-arcade downflows (SADs), and we investigate the largest SADs with continuous Hinode X-ray Telescope observations. The measured maximum width of the SADs in this event is at least 3 times the maximum width of SADs observed in AR flares, whereas the velocities of the largest SADs are similar to the typical values of AR SADs. The kinetic characteristics of the largest SADs observed in this event align with previous model predictions, where SADs originate from the nonlinear development of Rayleigh─Taylor-type instabilities. In this scenario, the larger system size allows the existence of larger-scale instabilities, while the development of the velocities of these instabilities is expected to be independent of the system size. Compared to AR flares, the temperature and emission measure in this event are lower, and there is less overall radiation, resulting in no evident Geostationary Operational Environmental Satellite signature. Similar to those in AR flares, SADs show lower temperatures compared to the surrounding fan plasma. Our observations show that SADs are present in a wide variety of eruptions. The reconnection mechanisms present in quiescent filament eruptions are similar to those driving more compact eruptions originating from ARs.

Keywords: Solar magnetic reconnection, Plasma physics, Solar x-ray emission, Quiescent solar prominence, Solar physics, Solar filament eruptions, Solar corona, Solar activity
Simulation of Solar Surface Flux Transport Constrained by Magnetic Power Spectra. I. Flux Transport Parameter. The multiscale structure of the solar surface magnetic field is essential for understanding both the Sun's internal dynamo processes and its external magnetic activity. The surface flux transport (SFT) model has been successful in describing the large-scale evolution of the surface field, but its ability to capture observed multiscale features, quantified by magnetic power spectra, remains uncertain. Here, we evaluate the SFT model by comparing observed and simulated power spectra across a broad range of spatial scales and by analyzing the effects of key transport parameters. We find that the simulations reproduce the observed spectra well at spherical harmonic degrees l ≲ 60, but diverge progressively at smaller spatial scales, l ≳ 60. This divergence likely arises from the diffusion approximation used to model the random walk of supergranulation. Power at 20 ≲ l ≲ 60 is primarily determined by the magnetic flux sources, while at l ≲ 20 the spectra are more sensitive to transport parameters. The meridional flow profile, including its equatorial gradient, peak latitude, and polar distribution, along with turbulent diffusivity, has distinct impacts on the low-degree modes (l ≤ 5). In particular, a comparison of the l = 3 and l = 5 multipoles strengths suggests that the poleward flow above ∼±60° latitudes is very weak. This study presents the first quantitative validation of SFT models using magnetic power spectra and provides a new constraint on surface flux transport physics.

Keywords: Solar cycle, Solar surface, Solar active regions, Solar physics, Solar magnetic fields, Solar meridional circulation
SN 2019hnl: A Type IIP Supernova with a Partially Stripped, Low-mass Progenitor. We present optical photometry and spectroscopy of SN 2019hnl. Discovered within ∼26 hr of explosion by the ATLAS survey, SN 2019hnl is a typical Type IIP supernova (SN) with a peak absolute V-band magnitude of −16.7 ± 0.1 mag, a plateau length of ∼107 days, and an early decline rate of 0.0086 ± 0.0006 mag (50 days)−1. We use nebular spectroscopy and hydrodynamic modeling with the SNEC, MESA, and STELLA codes to infer that the progenitor of SN 2019hnl was an MZAMS ∼ 11M⊙ red supergiant, which produced 0.047 ± 0.007M⊙ of 56Ni in the explosion. As a part of our hydrodynamic modeling, we reduced hydrogen envelope mass by scaling the mass loss within the "Dutch" wind scheme to fit our light curve, showing that the progenitor of a relatively typical Type IIP SN may experience partial stripping during their evolution and establish massive (∼0.2M⊙) circumstellar material environments prior to core collapse.

Keywords: Hydrodynamical simulations, Core-collapse supernovae, Type II supernovae, Stellar mass loss, Circumstellar matter
OTI on FIRE: Testing the Efficacy of Orbital Torus Imaging to Recover the Galactic Potential. Orbital Torus Imaging (OTI) is a dynamical inference method for determining the Milky Way's gravitational potential using stellar survey data. OTI uses gradients in stellar astrophysical quantities, such as element abundances, as functions of dynamical quantities, like orbital actions or energy, to estimate the Galactic mass distribution, assuming axisymmetry and a steady state of the system. While preliminary applications of OTI have shown promising outcomes, its sensitivity to disequilibrium effects is unknown. Here, we apply OTI to a benchmark Feedback in Realistic Environments (FIRE-2) cosmological hydrodynamic simulation, m12i, which enables a comparative analysis between known FIRE-2 vertical acceleration profiles and total surface mass densities to the analogous OTI-inferred results. We quantify OTI's accuracy within 16 solar-analog volumes embedded in the simulated galactic disk. Despite a dynamically evolving system, we find that OTI recovers the known vertical acceleration profiles within 3σ/1σ errors for 94%/75% of the volumes considered. We discuss the method's sensitivity to the local, instantaneous structure of the disk, reporting a loss in accuracy for volumes that have large (&gt;1.5 kpc) scale heights and low total density at z = 1.1 kpc. We present realistic OTI error bars from both Markov Chain Monte Carlo sampling and bootstrapping the FIRE-2 simulated data, which provides a touchstone for interpreting results obtained from current and forthcoming surveys such as SDSS-V, Gaia, WEAVE, and 4MOST.

Keywords: Hydrodynamical simulations, Stellar kinematics, Galaxy dynamics, Chemical abundances, Computational methods
Feature Intensity Mapping: Polycyclic Aromatic Hydrocarbon Emission from All Galaxies Across Cosmic Time. Line intensity mapping (LIM) is an emerging technique for probing the aggregate emission of a spectral line from all sources, without requiring individual detections. Through the wavelength─redshift relation, one can map the line-of-sight evolution of the line emission that traces the underlying large-scale structure in a spectral-imaging survey. In this work, we present a new technique—feature intensity mapping—as an extension of the LIM formalism to map broad spectral features in 3D, rather than the narrow emission lines typically targeted by LIM. By accounting for the convolution of spectral features with the instrument's spectral response across redshift, our technique enables simultaneous constraints on the redshift-dependent emission from multiple features. This approach enables 3D intensity mapping with some of the brightest features in the infrared spectra of galaxies: the polycyclic aromatic hydrocarbon (PAH) emission bands. We forecast the detectability of PAH signals using feature intensity mapping with the ongoing SPHEREx mission in the near-infrared and the proposed PRIMA mission in the far-infrared. We find that a signal-to-noise ratio of ≳10 per redshift bin of widths ∆z = 0.1 and 0.5 can be achieved at z &lt; 0.5 and 1 &lt; z &lt; 5 with SPHEREx and PRIMA, respectively, for multiple PAH features, suggesting a promising prospect for mapping the aggregate PAH emission at cosmological distances with upcoming data sets.

Keywords: Interstellar line emission, Polycyclic aromatic hydrocarbons, Cosmic background radiation, Large-scale structure of the universe
Determining the 3D Dynamics of Solar Flare Magnetic Reconnection. Solar flares are major space weather events that result from the explosive conversion of stored magnetic energy into bulk motion, plasma heating, and particle acceleration. While the standard flare model has proven highly successful in explaining key morphological features of flare observations, many aspects of the energy release are not yet understood. In particular, the turbulent three-dimensional structure of the flare current sheet is thought to play an important role in fast reconnection, particle acceleration, and bursty dynamics. Although direct diagnosis of the magnetic field dynamics in the corona remains highly challenging, rich information may be gleaned from flare ribbons, which represent the chromospheric imprints of reconnection in the corona. Intriguingly, recent solar imaging observations have revealed a diversity of fine structure in flare ribbons that hints at corresponding complexity in the reconnection region. We present high-resolution three-dimensional magnetohydrodynamics simulations of an eruptive flare and describe our efforts to interpret fine-scale ribbon features in terms of the current sheet dynamics. In our model, the current sheet is characterized by many coherent magnetic structures known as plasmoids. We derive a model analog for ribbons by generating a time series of field-line length maps (L-maps) and identifying abrupt shortenings as flare reconnection events. We thereby demonstrate that plasmoids imprint transient "spirals" along the analog of the ribbon front, with a morphology consistent with observed fine structure. We discuss the implications of these results for interpreting SolO, Interface Region Imaging Spectrograph, and Daniel K. Inouye Solar Telescope observations of explosive flare energy release.

Keywords: Solar active region magnetic fields, Magnetohydrodynamics, Solar flares, Solar magnetic reconnection, Solar active regions, Solar physics, Solar coronal mass ejections, Solar corona, Solar activity, Magnetohydrodynamical simulations
Star Formation Rates, Metallicities, and Stellar Masses on Kiloparsec Scales in TNG50. Integral field units have extended our knowledge of galactic properties to kiloparsec (or, sometimes, even smaller) patches of galaxies. These scales are where the physics driving galaxy evolution (feedback, chemical enrichment, etc.) take place. Quantifying the spatially resolved properties of galaxies, both observationally and theoretically, is therefore critical to our understanding of galaxy evolution. To this end, we investigate spatially resolved scaling relations within galaxies of M⋆ &gt; 109.0 at z = 0 in IllustrisTNG. We examine both the resolved star formation main sequence (rSFMS) and the resolved mass─metallicity relation (rMZR) using 1 kpc × 1 kpc maps. We find that the rSFMS in IllustrisTNG is well described by a power law but is significantly shallower than the observed rSFMS. However, the disagreement between the rSFMS of IllustrisTNG and observations is likely driven by an overestimation of AGN feedback in IllustrisTNG for the higher-mass hosts. Conversely, the rMZR for IllustrisTNG has very good agreement with observations. Furthermore, we argue that the rSFMS is an indirect result of the Schmidt─Kennicutt law and local gas relation, which are both independent of host galaxy properties. Finally, we expand upon a localized leaky-box model to study the evolution of idealized spaxels and find that it provides a good description of these resolved relations. The degree of agreement, however, between idealized spaxels and simulated spaxels depends on the "net" outflow rate for the spaxel, and the IllustrisTNG scaling relations indicate a preference for a low net outflow rate.

Keywords: Galaxy formation, Galaxy structure