Sazuna/UAT_keywords huggingface dataset:
Probing Disk Ice Content and Polycyclic Aromatic Hydrocarbon Emission through Multiband MagAO+Clio Images of HD 141569. We present resolved images of the inner disk component around HD 141569A using the Magellan adaptive optics system with the Clio2 1-5 μm camera, offering a glimpse of a complex system thought to be in a short evolutionary phase between protoplanetary and debris disk stages. We use a reference star along with the Karhunen-Loéve image projection (KLIP) algorithm for point-spread function subtraction to detect the disk inward to about 0.″24 (~25 au assuming a distance of 111 pc) at high signal-to-noise ratios at $L^{\prime} $ (3.8 μm), Ls (3.3 μm), and narrowband Ice (3.1 μm). We identify an arc or spiral arm structure at the southeast extremity, consistent with previous studies. We implement forward modeling with a simple disk model within the framework of a Markov Chain Monte Carlo sampler to better constrain the geometrical attributes and photometry using our KLIP-reduced disk images. We then leverage these modeling results to facilitate a comparison of the measured brightness in each passband to find a reduction in scattered light from the disk in the Ice filter, implying significant absorption due to water ice in the dust. Additionally, our best-fit disk models exhibit peak brightness in the southwestern, back-scattering region of the disk, which we suggest to be possible evidence of 3.3 μm polycyclic aromatic hydrocarbon emission. However, we point out the need for additional observations with bluer filters and more complex modeling to confirm these hypotheses.

Keywords: High contrast techniques, Direct imaging, Protoplanetary disks, Adaptive optics
Assessing the Observability of Deep Meridional Flow Cells in the Solar Interior. Meridional circulation regulates the Sun's interior dynamics and magnetism. While it is well accepted that meridional flows are poleward at the Sun's surface, helioseismic observations have yet to provide a definitive answer for the depth at which those flows return to the equator, or the number of circulation cells in depth. Here, we explore the observability of multiple circulation cells stacked in radius. Specifically, we examine the seismic signature of several meridional flow profiles by convolving time-distance averaging kernels with mean flows obtained from a suite of 3D hydrodynamic simulations. At mid and high latitudes, we find that weak flow structures in the deep convection zone can be obscured by signals from the much stronger surface flows. This contamination of 1-2 m s-1 is caused by extended side lobes in the averaging kernels, which produce a spurious equatorward signal with flow speeds that are 1 order of magnitude stronger than the original flow speeds in the simulations. At low latitudes, the flows in the deep layers of the simulations are stronger (&gt;2 m s-1) and multiple cells across the convection zone can produce a sufficiently strong signal to survive the convolution process. Now that meridional flows can be measured over two decades of data, the uncertainties arising from convective noise have fallen to a level where they are comparable in magnitude to the systematic biases caused by nonlocal features in the averaging kernels. Hence, these systematic errors are beginning to influence current helioseismic deductions and need broader consideration.

Keywords: Helioseismology, Hydrodynamical simulations, Solar interior, Solar meridional circulation
Using Potential Field Extrapolations to Explore the Origin of Type II Spicules. We used 29 high-resolution line-of-sight magnetograms acquired with the Goode Solar Telescope (GST) in a quiet-Sun area to extrapolate a series of potential field configurations and study their time variations. The study showed that there are regions that consistently exhibit changes in loop connectivity, whereas other vast areas do not show such changes. Analysis of the topological features of the potential fields indicates that the photospheric footprint of the separatrix between open- and closed-loop systems closely matches the roots of rapid blue- and redshifted excursions, which are disk counterparts of type II spicules. There is a tendency for the footpoints of the observed H α  features to be cospatial with the footpoints of the loops that most frequently change their connectivity, while the area occupied by the open fields that did not show any significant and persistent connectivity changes is void of prominent jet and spicular activity. We also detected and tracked magnetic elements using the Southwest Automatic Magnetic Identification Suite and GST magnetograms, which allowed us to construct artificial magnetograms and calculate the corresponding potential field configurations. Analysis of the artificial data showed tendencies similar to those found for the observed data. The present study suggests that a significant amount of chromospheric activity observed in the far wings of the H α  spectral line may be generated by reconnecting closed-loop systems and canopy fields consisting of "open" field lines.

Keywords: Solar spicules, Solar chromosphere, Solar mottles
The Diffusion and Scattering of Accelerating Particles in Compressible MHD Turbulence. We numerically study the diffusion and scattering of cosmic rays (CRs) together with their acceleration processes in the framework of the modern understanding of magnetohydrodynamic (MHD) turbulence. Based on the properties of compressible MHD turbulence obtained from observations and numerical experiments, we investigate the interaction of CRs with plasma modes. We find that (1) the gyroradius of particles exponentially increases with the acceleration timescale; (2) the momentum diffusion presents the power-law relationship with the gyroradius in the strong turbulence regime, and shows a plateau in the weak turbulence regime implying a stochastic acceleration process; (3) the spatial diffusion is dominated by the parallel diffusion in the sub-Alfvénic regime, while it is dominated by the perpendicular diffusion in the super-Alfvénic one; (4) as for the interaction of CRs with plasma modes, the particle acceleration is dominated by the fast mode in the high β case, while in the low β case, it is dominated by the fast and slow modes; and (5) in the presence of acceleration, magnetosonic modes still play a critical role in the diffusion and scattering processes of CRs, which is in good agreement with earlier theoretical predictions.

Keywords: Magnetohydrodynamics, Interplanetary turbulence, Interplanetary particle acceleration, Interstellar medium, Cosmic rays
A Machine Learning Approach to Understanding the Physical Properties of Magnetic Flux Ropes in the Solar Wind at 1 au. Interplanetary magnetic flux ropes (MFRs) are commonly observed structures in the solar wind, categorized as magnetic clouds (MCs) and small-scale MFRs (SMFRs) depending on whether they are associated with coronal mass ejections. We apply machine learning to systematically compare SMFRs, MCs, and ambient solar wind plasma properties. We construct a data set of 3-minute averaged sequential data points of the solar wind's instantaneous bulk fluid plasma properties using about 20 years of measurements from Wind. We label samples by the presence and type of MFRs containing them using a catalog based on Grad-Shafranov (GS) automated detection for SMFRs and NASA's catalog for MCs (with samples in neither labeled non-MFRs). We apply the random forest machine learning algorithm to find which categories can be more easily distinguished and by what features. MCs were distinguished from non-MFRs with an area under the receiver-operator curve (AUC) of 94% and SMFRs with an AUC of 89%, and had distinctive plasma properties. In contrast, while SMFRs were distinguished from non-MFRs with an AUC of 86%, this appears to rely solely on the &gt; 5 nT threshold applied by the GS catalog. The results indicate that SMFRs have virtually the same plasma properties as the ambient solar wind, unlike the distinct plasma regimes of MCs. We interpret our findings as additional evidence that most SMFRs at 1 au are generated within the solar wind. We also suggest that they should be considered a salient feature of the solar wind's magnetic structure rather than transient events.

Keywords: Random Forests, Solar wind, Heliosphere
Unobscured Central Broad-line Regions in Type-1.9 AGN SDSS J1241+2602. Strong evidence is reported to support unobscured broad-line regions (BLRs) in Type-1.9 active galactic nucleus (AGN) SDSS J1241+2602 with reliable broad Hα but no broad Hβ. Commonly, the disappearance of broad Hβ can be explained by the AGN unified model, in which heavily obscured BLRs are expected in Type-1.9 AGNs. Here, based on properties of two kinds of BH masses, the virial BH mass and the BH mass obtained through the M BH-σ relation, an independent method is proposed to test whether there are unobscured central BLRs in a Type-1.9 AGN. By the reliable measurement of stellar velocity dispersion of about 110 ± 12 km s -1 through the host galaxy absorption features in SDSS J1241+2602, the BH mass obtained through the M BH-σ relation is consistent with the virial BH mass (3.43 ± 1.25) × 107 M ⊙ determined through properties of the observed broad Hα without considering the effects of obscurations in SDSS J1241+2602. Meanwhile, if considering heavily obscured BLRs in SDSS J1241+2602, the reddening-corrected virial BH mass is tens of times larger than the value expected from M BH-σ, leading SDSS J1241+2602 to be an outlier in the M BH-σ space with a confidence level higher than 5σ. Therefore, unobscured BLRs are preferred in the Type-1.9 AGN SDSS J1241+2602. The results indicate that it is necessary to check whether unobscured central BLRs are common in Type-1.9 AGNs when testing the unified model of AGNs through properties of Type-1.9 AGNs.

Keywords: Supermassive black holes, Active galaxies, Active galactic nuclei, Emission line galaxies
Magnetohydrodynamic Perspective on the Disappearance of Mercury's Bow Shock by Helios Data Exploration. In the magnetohydrodynamic (MHD) perspective, the planet's bow shock would disappear when the fast-mode Mach number (M F) of the solar wind is less than one. Compared to Earth, Mercury is subject to a lower M F solar wind due to its proximity to the Sun, resulting in a higher possibility of the disappearance of its bow shock. To examine the variability of Mercury's bow shock in response to the solar wind properties, analyses of the observations by the Helios spacecraft at 0.30-0.50 au during 1975-1983, covering solar cycle 21, together with the theoretical solutions and MHD simulations are conducted in this study. Our observational analyses show that more solar wind data with extremely low fast-mode Mach numbers (say, M F ≤ 1.5) are observed during the rising and maximum phases and are characterized by a significantly low proton number density. It is also found that approximately 35% of the extremely low fast-mode Mach number solar wind events (M F ≤ 1.5) occur within the main body of interplanetary coronal mass ejections (ICMEs), while about 58% of them are unrelated to ICMEs. Three of these events are selected to demonstrate that the occurrences of the solar wind with M F ≤ 1.5 may not be necessarily affected by ICMEs. Our theoretical and numerical results indicate that when Mercury encounters the solar wind with M F ≤ 1.5, its bow shock would move farther away, become flattened, and even disappear. Furthermore, our calculations suggest that Mercury's bow shock would become a slow-mode shock with a concave-upward structure under such extreme solar wind conditions.

Keywords: Solar cycle, Magnetohydrodynamics, Solar wind, Planetary bow shocks, Mercury (planet)
Search for Galactic Core-collapse Supernovae in a Decade of Data Taken with the IceCube Neutrino Observatory. The IceCube Neutrino Observatory has been continuously taking data to search for ${ \mathcal O }(0.5\mbox{--}10)$ s long neutrino bursts since 2007. Even if a Galactic core-collapse supernova is optically obscured or collapses to a black hole instead of exploding, it will be detectable via the ${ \mathcal O }(10)$ MeV neutrino burst emitted during the collapse. We discuss a search for such events covering the time between 2008 April 17 and 2019 December 31. Considering the average data taking and analysis uptime of 91.7% after all selection cuts, this is equivalent to 10.735 yr of continuous data taking. In order to test the most conservative neutrino production scenario, the selection cuts were optimized for a model based on an 8.8 solar mass progenitor collapsing to an O-Ne-Mg core. Conservative assumptions on the effects of neutrino oscillations in the exploding star were made. The final selection cut was set to ensure that the probability to detect such a supernova within the Milky Way exceeds 99%. No such neutrino burst was found in the data after performing a blind analysis. Hence, a 90% C.L. upper limit on the rate of core-collapse supernovae out to distances of ≈25 kpc was determined to be 0.23 yr-1. For the more distant Magellanic Clouds, only high neutrino luminosity supernovae will be detectable by IceCube, unless external information on the burst time is available. We determined a model-independent limit by parameterizing the dependence on the neutrino luminosity and the energy spectrum.

Keywords: Neutrino telescopes, Supernova neutrinos, Core-collapse supernovae
The California-Kepler Survey. XI. A Survey of Chromospheric Activity through the Lens of Precise Stellar Properties. Surveys of exoplanet host stars are valuable tools for assessing population level trends in exoplanets, and their outputs can include stellar ages, activity, and rotation periods. We extracted chromospheric activity measurements from the California-Kepler Survey Gaia survey spectra in order to probe connections between stellar activity and fundamental stellar properties. Building on the California Kepler Survey's legacy of 1189 planet host star stellar properties including temperature, surface gravity metallicity, and isochronal age, we add measurements of the Ca II H and K lines as a proxy for chromospheric activity for 879 planet hosting stars. We used these chromospheric activity measurements to derive stellar rotation periods. We find a discrepancy between photometrically derived and activity-derived rotation periods for stars on the Rossby Ridge. These results support the theory of weakened magnetic braking. We find no evidence for metallicity-dependent activity relations, within the metallicity range of -0.2 to +0.3 dex. With our single epoch spectra we identify stars that are potentially in Maunder minimum-like state using a combination of log( ${R}_{\mathrm{HK}}^{{\prime} }$ ) and position below the main sequence. We do not yet have the multiyear time series needed to verify stars in Maunder minimum-like states. These results can help inform future theoretical studies that explore the relationship between stellar activity, stellar rotation, and magnetic dynamos.

Keywords: Exoplanet astronomy, Stellar chromospheres, Stellar activity
The Dependence of the Structure of Planet-opened Gaps in Protoplanetary Disks on Radiative Cooling. Planets can excite density waves and open annular gas gaps in protoplanetary disks. The depth of gaps is influenced by the evolving angular momentum carried by density waves. While the impact of radiative cooling on the evolution of density waves has been studied, a quantitative correlation to connect gap depth with the cooling timescale is lacking. To address this knowledge gap, we employ the grid-based code Athena++ to simulate disk-planet interactions, treating cooling as a thermal relaxation process. We establish quantitative dependencies of steady-state gap depth (Equation 36) and width (Equation 41) on planetary mass, Shakura-Sunyaev viscosity, disk scale height, and thermal relaxation timescale (β). We confirm previous results that gap opening is the weakest when the thermal relaxation timescale is comparable to the local dynamical timescale. Significant variations in gap depth, up to an order of magnitude, are found with different β. In terms of width, a gap is at its narrowest around β = 1, approximately 10%-20% narrower compared to the isothermal case. When β ~ 100, it can be ~20% wider, and higher viscosity enhances this effect. We derive possible masses of the gas gap-opening planets in AS 209, HD 163296, MWC 480, and HL Tau, accounting for the uncertainties in the local thermal relaxation timescale.

Keywords: Planetary system formation, Planetary-disk interactions, Protoplanetary disks, Planet formation
Small-scale Cosmic-Ray Anisotropy Observed by the GRAPES-3 Experiment at TeV Energies. GRAPES-3 is a mid-altitude (2200 m) and near-equatorial (11.°4N) air shower array, overlapping in its field of view for cosmic-ray observations with experiments that are located in the Northern and Southern Hemispheres. We analyze a sample of 3.7 × 109 cosmic-ray events collected by the GRAPES-3 experiment between 2013 January 1 and 2016 December 31 with a median energy of ~16 TeV for study of small-scale (&lt;60°) angular-scale anisotropies. We observed two structures, labeled A and B, that deviate from the expected isotropic distribution of cosmic rays in a statistically significant manner. Structure A spans 50°-80° in R.A. and from -15° to 30° in decl. The relative excess observed in structure A is at the level of (6.5 ± 1.3) × 10-4 with a statistical significance of 6.8 standard deviations. Structure B is observed in the R.A. range 110°-140° and at decl. from -10° to 30°. The relative excess observed in this region is at the level of (4.9 ± 1.4) × 10-4 with a statistical significance of 4.7 standard deviations. These structures are consistent with those reported by Milagro, ARGO-YBJ, and HAWC. These observations could provide a better understanding of the sources of cosmic rays, their propagation, and the magnetic structures in our Galaxy.

Keywords: Galactic cosmic rays
Comparative Analysis of Type III Radio Bursts and Solar Flares: Spatial Localization and Correlation with Solar Flare Intensity. We present a comprehensive study of type III radio bursts and their association with solar flares of magnitude M1.0 and larger, as observed by four widely separated spacecraft (Parker Solar Probe, Solar Orbiter, STEREO-A, and Wind). Our main focus is the introduction and validation of two methods for localizing radio bursts using the available multispacecraft data. The first method utilizes intensity fitting with a circular Gaussian distribution, while the second method is based on the time arrival of radio bursts. We demonstrate the effectiveness of these methods through the analysis of a single type III burst event and compare their results with the traditional radio triangulation technique. Furthermore, we conduct a statistical study of 17 type III bursts associated with M- and X-class solar flares in years 2020-2022. Our findings suggest a possible correlation between solar flare intensities and longitudes, with east limb flares tending to be weaker than west limb flares. We also observe a systematic drift of radio burst longitudes toward the east, potentially explained by a poleward component of the local density gradient. Our results suggest a strong correlation between solar flare intensities and radio burst properties, enhancing our understanding of the relationship between solar flares and type III radio bursts.

Keywords: Radio bursts, Solar flares, Radio astronomy
A Study of Primordial Very Massive Star Evolution. II. Stellar Rotation and Gamma-Ray Burst Progenitors. We calculate new evolutionary models of rotating primordial very massive stars, with initial mass from 100 M ⊙ to 200 M ⊙, for two values of the initial metallicity Z = 0 and Z = 0.0002. For the first time in this mass range, we consider stellar rotation and pulsation-driven mass loss, along with radiative winds. The models evolve from the zero-age main sequence until the onset of pair-instability. We discuss the main properties of the models during their evolution and then focus on the final fate and the possible progenitors of jet-driven events. All tracks that undergo pulsational-pair instability produce successful gamma-ray bursts (GRB) in the collapsar framework, while those that collapse directly to black holes (BH) produce jet-driven supernova events. In these latter cases, the expected black hole mass changes due to the jet propagation inside the progenitor, resulting in different models that should produce BH within the pair-instability black hole mass gap. Successful GRBs predicted here from zero metallicity, and very metal-poor progenitors, may be bright enough to be detected even up to redshift ~20 using current telescopes such as the Swift-BAT X-ray detector and the JWST.

Keywords: Gamma-ray bursts, Population III stars, Stellar winds, Stellar rotation, Stellar remnants, Stellar evolution
Protostellar Chimney Flues: Are Jets and Outflows Lifting Submillimeter Dust Grains from Disks into Envelopes?. Low dust opacity spectral indices (β &lt; 1) measured in the inner envelopes of class 0/I young stellar objects (age ~104-5 yr) have been interpreted as the presence of (sub-)millimeter dust grains in these environments. The density conditions and the lifetimes of collapsing envelopes have proven unfavorable for the growth of solids up to millimeter sizes. As an alternative, magnetohydrodynamical simulations suggest that protostellar jets and outflows might lift grains from circumstellar disks and diffuse them in the envelope. We reframe available data for the CALYPSO sample of Class 0/I sources and show tentative evidence for an anticorrelation between the value of β 1-3 mm measured in the inner envelope and the mass-loss rate of their jets and outflows, supporting a connection between the two. We discuss the implications that dust transport from the disk to the inner envelope might have for several aspects of planet formation. Finally, we urge for more accurate measurements of both correlated quantities and the extension of this work to larger samples, necessary to further test the transport scenario.

Keywords: Millimeter astronomy, Stellar jets, Stellar winds, Interstellar medium, Circumstellar dust, Planet formation
Identification of 4FGL Uncertain Sources at Higher Resolutions with Inverse Discrete Wavelet Transform. In the forthcoming era of big astronomical data, it is a burden to find target sources from ground-based and space-based telescopes. Although machine-learning methods have been extensively utilized to address this issue, the incorporation of in-depth data analysis can significantly enhance the efficiency of identifying target sources when dealing with massive volumes of astronomical data. In this work, we focused on the task of finding active galactic nucleus (AGN) candidates and identifying BL Lacertae objects (BL Lac) or flat spectrum radio quasar (FSRQ) candidates from the 4FGL_DR3 uncertain sources. We studied the correlations among the attributes of the 4FGL_DR3 catalog and proposed a novel method, named fractal dimension-inverse discrete wavelet transform (FDIDWT), to transform the original data. The transformed data set is characterized as low-dimensional and feature-highlighted, with the estimation of correlation features by fractal dimension theory and the multi-resolution analysis by inverse discrete wavelet transform (IDWT). Combining the FDIDWT method with an improved lightweight MatchboxConv1D model, we accomplished two missions: (1) to distinguish the AGNs from others (non-AGNs) in the 4FGL_DR3 uncertain sources with an accuracy of 96.65% ± 1.32%, namely Mission A; and (2) to classify blazar candidates of uncertain type into BL Lacs or FSRQs with an accuracy of 92.03% ± 2.2%, namely Mission B. There are 1354 AGN candidates in Mission A, and 482 BL Lacs candidates and 128 FSRQ candidates were found in Mission B. The results show a high consistency of greater than 98% with the results in previous works. In addition, our method has the advantage of finding less variable and relatively faint sources than ordinary methods.

Keywords: Blazars, Active galactic nuclei, Classification, Wavelet analysis