Sazuna/UAT_keywords huggingface dataset:
Sensitivity of <SUP>44</SUP>Ti and <SUP>56</SUP>Ni Production in Core-collapse Supernova Shock-driven Nucleosynthesis to Nuclear Reaction Rate Variations. Recent observational advances have enabled high resolution mapping of 44Ti in core-collapse supernova (CCSN) remnants. Comparisons between observations and models provide stringent constraints on the CCSN mechanism. However, past work has identified several uncertain nuclear reaction rates that influence 44Ti and 56Ni production in postprocessing model calculations. We evolved one-dimensional models of 15 M⊙, 18 M⊙, 22 M⊙, and 25 M⊙ stars from zero age main sequence through CCSN using Modules for Experiments in Stellar Astrophysics and investigated the previously identified reaction rate sensitivities of 44Ti and 56Ni production. We tested the robustness of our results by making various assumptions about the CCSN explosion energy and mass cut. We found a number of reactions that have a significant impact on the nucleosynthesis of 44Ti and 56Ni, particularly for lower progenitor masses. Notably, the reaction rates ${}^{13}{\rm{N}}{(\alpha ,p)}^{16}{\rm{O}}$ , ${}^{17}{\rm{F}}{(\alpha ,p)}^{20}\mathrm{Ne}$ , ${}^{52}\mathrm{Fe}{(\alpha ,p)}^{55}\mathrm{Co}$ , ${}^{56}\mathrm{Ni}{(\alpha ,p)}^{59}\mathrm{Cu}$ , ${}^{57}\mathrm{Ni}{(n,p)}^{57}\mathrm{Co}$ , ${}^{56}\mathrm{Co}{(p,n)}^{56}\mathrm{Ni}$ , ${}^{39}{\rm{K}}{(p,\gamma )}^{40}\mathrm{Ca}$ , ${}^{47}{\rm{V}}{(p,\gamma )}^{48}\mathrm{Cr}$ , ${}^{52}\mathrm{Mn}{(p,\gamma )}^{53}\mathrm{Fe}$ , ${}^{57}\mathrm{Co}{(p,\gamma )}^{58}\mathrm{Ni}$ , and ${}^{39}{\rm{K}}{(p,\alpha )}^{36}\mathrm{Ar}$ are influential for a large number of model conditions. Furthermore, we found the list of influential reactions identified by previous postprocessing studies of CCSN shock-driven nucleosynthesis is likely incomplete, motivating future larger-scale sensitivity studies.

Keywords: Astrophysical explosive burning, Explosive nucleosynthesis, Core-collapse supernovae
RELICS: A Very Large (θ<SUB>E</SUB> ∼ 40″) Cluster Lens—RXC J0032.1+1808. Extensive surveys with the Hubble Space Telescope over the past decade, targeting some of the most massive clusters in the sky, have uncovered dozens of galaxy cluster strong lenses. The massive cluster strong-lens scale is typically θE ∼ 10″ to ∼30″-35″, with only a handful of clusters known with Einstein radii θE ∼ 40″ or above (for zsource = 2, nominally). Here we report another very large cluster lens, RXC J0032.1+1808 (z = 0.3956), the second-richest cluster in the redMapper cluster catalog and the 85th most massive cluster in the Planck Sunyaev-Zel'dovich catalog. With our light-traces-mass and fully parametric approaches, we construct strong-lensing models based on 18 multiple images of five background galaxies newly identified in the Hubble data, mainly from the Reionization Lensing Cluster Survey (RELICS), in addition to a known sextuply imaged system in this cluster. Furthermore, we compare these models to Lenstool and GLAFIC models that were produced independently as part of the RELICS program. All models reveal a large effective Einstein radius of θE ≃ 40″ (zsource = 2), owing to the obvious concentration of substructures near the cluster center. Although RXC J0032.1+1808 has a very large critical area and high lensing strength, only three magnified high-redshift candidates are found within the field targeted by RELICS. Nevertheless, we expect many more high-redshift candidates will be seen in wider and deeper observations with Hubble or the James Webb Space Telescope. Finally, the comparison between several algorithms demonstrates that the total error budget is largely dominated by systematic uncertainties.

Keywords: Galaxy clusters, Strong gravitational lensing
The Streaming Instability in Two-dimensional Protoplanetary Disks. We conduct a two-dimensional (2D) stability analysis for the aerodynamically coupled system of gas and dust in protoplanetary disks using the WKB approximation. The 2D analysis may apply to a vertically integrated disk or a thin dust layer at the disk midplane. We show that the streaming instability exists in 2D and examine the growth rate and its dependence on the mean dust-to-gas ratio, $\bar{\epsilon }$ , and the Stokes number, St. For small $\bar{\epsilon }$ , the dust back reaction may be viewed as a perturbation to the wave system, and analytical results are successfully derived by the method of perturbation with respect to $\bar{\epsilon }$ . At a given azimuthal wavenumber, m, the growth rate as a function of the radial wavenumber, kr, shows a peak corresponding to the resonance between the relative drift velocity and the Rossby/trivial waves in the gas. For small $\bar{\epsilon }$ , the peak growth rate at resonant modes increases as m1/2 when the Rossby wave effect is negligible and the gas wave becomes trivial. With increasing St, the peak growth rate increases as St1/2 at St ≪ 1, peaks at St ∼ 1, and finally decreases as St-1/2 for St ≫ 1. We find that the growth rate scales with $\bar{\epsilon }$ as ${\bar{\epsilon }}^{1/2}$ at $\bar{\epsilon }\ll 1$ and peaks at $\bar{\epsilon }\sim 1$ . The instability is physically interpreted as a runaway process of dust trapping in relative drift-induced anticyclonic vortices. The effects of the compressibility and viscosity of the gas, the applicability of the WKB application, and the effects of the Keplerian shear are discussed.

Keywords: Astrophysical fluid dynamics, Protoplanetary disks, Planet formation, Planetesimals
The Axisymmetric Streaming Instability in Protoplanetary Disks. We reexamine the streaming instability in protoplanetary disks under the axisymmetric geometry. We identify the roles of all the relevant physical processes and clarify the clustering mechanism of dust, offering a new physical interpretation. Through back-reaction, the dust density fluctuations in combination with the mean relative drift velocity provide a source for the gas velocity, which in turn drives the velocity and divergence of the dust flow. In the limit where the dust-to-gas ratio $\bar{\epsilon }\ll 1$ , the action of the Coriolis force on the radial gradient of the azimuthal dust velocity generates the divergence of the dust. In the opposite limit $\bar{\epsilon }\gg 1$ , the vertical gradient of the vertical dust velocity makes the main contribution to the dust divergence. The different dust clustering mechanisms at $\bar{\epsilon }\ll 1$ and $\bar{\epsilon }\gg 1$ are referred to as Mode I and Mode II, respectively. In both cases, the dust divergence further enhances the dust density fluctuations, resulting in a positive feedback loop. In Mode I (or Mode II), the growth rate is contributed by the mean azimuthal (or radial) drag force in the gas equation of motion, while the mean radial (or azimuthal) drag tends to reduce it. The instability makes a transition from Mode I to Mode II when the coupling between the perturbed gas and dust velocities is stronger than the Coriolis force in the gas equations, which occurs at $\bar{\epsilon }\simeq 1$ and $\bar{\epsilon }\simeq {St}$ for Stokes numbers St &lt; 1 and St &gt; 1, respectively.

Keywords: Astrophysical fluid dynamics, Protoplanetary disks, Planet formation, Planetesimals
Hybrid Very Long Baseline Interferometry Imaging and Modeling with THEMIS. Generating images from very long baseline interferometric observations poses a difficult, and generally not unique, inversion problem. This problem is simplified by the introduction of constraints, some generic (e.g., positivity of the intensity) and others motivated by physical considerations (e.g., smoothness, instrument resolution). It is further complicated by the need to simultaneously address instrumental systematic uncertainties and sparse coverage in the u-v plane. We report a new Bayesian image reconstruction technique in the parameter estimation framework THEMIS that has been developed for the Event Horizon Telescope. This has two key features: first, the full Bayesian treatment of the image reconstruction makes it possible to generate a full posterior for the images, permitting a rigorous and quantitative investigation into the statistical significance of image features. Second, it is possible to seamlessly incorporate directly modeled features simultaneously with image reconstruction. We demonstrate this second capability by incorporating a narrow, slashed ring in reconstructions of simulated M87 data in an attempt to detect and characterize the photon ring. We show that it is possible to obtain high-fidelity photon ring sizes, enabling mass measurements with accuracies of 2%-5% that are essentially insensitive to astrophysical uncertainties, and creating opportunities for precision tests of general relativity.

Keywords: Black hole physics, Computational astronomy, Astronomy data modeling, Long baseline interferometry, General relativity, Submillimeter astronomy
Circumbinary Disks of the Protostellar Binary Systems in the L1551 Region. We report Atacama Large Millimeter/submillimeter Array Cycle 4 observations of the Class I binary protostellar system L1551 IRS 5 in the 0.9 mm continuum emission, C18O (J = 3-2), OCS (J = 28-27), and four other Band 7 lines. At ∼0"07 (=10 au) resolution in the 0.9 mm emission, two circumstellar disks (CSDs) associated with the binary protostars are separated from the circumbinary disk (CBD). The CBD is resolved into two spiral arms, one connecting to the CSD around the northern binary source, Source N, and the other to Source S. As compared to the CBD in the neighboring protobinary system L1551 NE, the CBD in L1551 IRS 5 is more compact (r ∼ 150 au) and the m = 1 mode of the spirals found in L1551 NE is less obvious in L1551 IRS 5. Furthermore, the dust and molecular-line brightness temperatures of CSDs and CBD reach &gt;260 and &gt;100 K, respectively, in L1551 IRS 5, much hotter than those in L1551 NE. The gas motions in the spiral arms are characterized by rotation and expansion. Furthermore, the transitions from the CBD to the CSD rotations at around the L2 and L3 Lagrangian points and gas motions around the L1 point are identified. Our numerical simulations reproduce the observed two spiral arms and expanding gas motion as a result of gravitational torques from the binary, transitions from the CBD to the CSD rotations, and the gas motion around the L1 point. The higher temperature in L1551 IRS 5 likely reflects the inferred FU Ori event.

Keywords: Star formation, Interstellar medium
Impact of Ordered and Disordered Magnetic Fields on Multiwavelength Emission of Blazars. We present a detailed analysis of the effects of magnetic field topology on the spectral energy distribution (SED) and spectral variability patterns (SVPs) of blazars. In order to study these effects, we have extended our time-dependent leptonic jet model (in the internal shock scenario) to include the dependence of the synchrotron emissivity on the angle between the photon direction and the magnetic field in the plasma frame. We have explored the effects of different magnetic field geometries, such as parallel, perpendicular, oblique, toroidal, and helical, on the simulated SEDs and SVPs of a generic blazar for both purely ordered and disordered components of fields. These considerations provide either upper or lower limits to the impact on blazar emission, depending on the fraction of a disordered component present and the viewing angle. The results of our work point out some of the signatures that the orientations can leave on the SEDs and SVPs of a blazar. For example, in the case of a purely oblique field, if the magnetic field is aligned along the line of sight (in the plasma frame), it results in an annulment of the synchrotron component while keeping the flux level of the high-energy component intact. On the other hand, in the presence of a disordered component, the impact of an oblique field is reduced, and the same effect is not observed.

Keywords: Hydrodynamical simulations, High energy astrophysics, Blazars, Relativistic jets, Plasma astrophysics, Radiative transfer simulations, Radiative transfer equation, Active galactic nuclei, Radiative transfer, Radiative processes, Shocks, Magnetic fields
The Interaction of Type Iax Supernova Ejecta with a Helium Companion Star. Type Iax supernovae (SNe Iax) are an important subluminous class of SNe Ia. However, their progenitors and explosion mechanisms are not yet understood. It has been suggested that SNe Iax may be produced from weak deflagration explosions of Chandrasekhar-mass white dwarfs (WDs) in binary systems with a helium (He) star donor. In such progenitor systems, the stripped He companion material caused by the ejecta-companion interaction is expected to present some He features in their late-time spectra. However, the detection of He lines in late-time spectra of SNe Iax has not yet been successful, which gives an upper limit on the amount of stripped He mass of $\lesssim 2\times {10}^{-3}-0.1$ ${M}_{\odot }$ . In this work, we study the interaction between SN Iax ejecta and a He star companion by performing three-dimensional hydrodynamical simulations with a weak pure deflagration explosion model. We find that about $4\times {10}^{-3}$ ${M}_{\odot }$ of He material can be stripped off from the companion star by SN explosion, which is very close to (or lower than) the observational upper limit on the total stripped He mass in SNe Iax. We, therefore, conclude that nondetection of He lines in late-time spectra of SNe Iax could be reasonably explained if they indeed resulted from weak pure deflagration explosions of Chandrasekhar-mass WDs in progenitor systems with a He star donor.

Keywords: Close binary stars, Hydrodynamical simulations, Type Ia supernovae, Chandrasekhar limit
Prebiotic Cytosine Synthesis from Urea in Interstellar Space: A Computational Mechanistic Study. The potential energy surfaces for the formation of cytosine (Cyt) and a protonated cytosine (CytH+) from reactions of urea with cyanoacetylene (CA), cyanoacetaldehyde (CAA), or their protonated ions, CAAH+ and CAH+ with or without H2O, have been determined from quantum chemical calculation using the CBS-QB3 method. The overall activation energies of the formation of Cyt or CytH+ from urea + CA, urea + CAA and, urea + CAH+ are 127, 211, and 31 kJ mol-1, respectively, which are too high for the thermal reactions to occur in the interstellar medium (ISM). The barrierless reaction pathways have been proposed for the formation of CytH+ from urea + CAH++ H2O and urea + CAAH+. A kinetic analysis shows that the synthesis of Cyt through the formation of CytH+ from urea, CAH+, and H2O would be possible in the ISM.

Keywords: Interstellar molecules, Astrobiology, Interstellar medium, Astrochemistry
Spectral Diversities of Gamma-Ray Bursts in High-energy Bands: Hints from Turbulent Cascade. We statistically examine the gamma-ray burst (GRB) photon indices obtained by the Fermi-GBM and Fermi-LAT observations and compare the LAT GRB photon indices to the GBM GRB photon indices. We apply the jitter radiation to explain the GRB spectral diversities in the high-energy bands. In our model, the jitter radiative spectral index is determined by the spectral index of the turbulence. We classify GRBs into three classes depending on the shape of the GRB high-energy spectrum when we compare the GBM and LAT detections: the GRB spectrum is concave (GRBs turn out to be softer and are labeled as S-GRBs), the GRB spectrum is convex (GRBs turn out to be harder and are labeled as H-GRBs), and the GRBs have no strong spectral changes (labeled as N-GRBs). A universal Kolmogorov index 7/3 in the turbulent cascade is consistent with the photon index of the N-GRBs. The S-GRB spectra can be explained by the turbulent cascade due to the kinetic magnetic reconnection with the spectral index range of the turbulence from 8/3 to 3.0. The H-GRB spectra originate from the inverse turbulent cascade with the spectral index range of the turbulence from 2.0 to 3.5 that occurred during the large lengthscale magnetic reconnection. Thus, the GRB radiative spectra are diversified because the turbulent cascade modifies the turbulent energy spectrum. More observational samples are expected in the future to further identify our suggestions.

Keywords: Magnetohydrodynamics, Gamma-ray bursts, Magnetic fields
Detection of the Diffuse H I Emission in the Circumgalactic Medium of NGC 891 and NGC 4565. We present detections of 21 cm emission from neutral hydrogen (H I) in the circumgalactic medium (CGM) of the local edge-on galaxies NGC 891 and NGC 4565 using the Robert C. Byrd Green Bank Telescope (GBT). With our 5σ sensitivity of $8.2\times {10}^{16}$ cm-2 calculated over a 20 km s-1 channel, we achieve $\gt 5\sigma $ detections out to $90\mbox{--}120\,\mathrm{kpc}$ along the minor axes. The velocity width of the CGM emission is as large as that of the disk $\approx 500$ km s-1, indicating the existence of a diffuse component permeating the halo. We compare our GBT measurements with interferometric data from the Westerbork Synthesis Radio Telescope (WSRT). The WSRT maps the H I emission from the disk at high signal-to-noise ratio but has limited surface brightness sensitivity at the angular scales probed with the GBT. After convolving the WSRT data to the spatial resolution of the GBT (FWHM = 9'1), we find that the emission detected by the WSRT accounts for ${48}_{-25}^{+15}$ % ( ${58}_{-18}^{+4}$ %) of the total flux recovered by the GBT from the CGM of NGC 891 (NGC 4565). The existence of significant GBT-only flux suggests the presence of a large amount of diffuse, low column density H I emission in the CGM. For reasonable assumptions, the extended diffuse H I could account for 5.2 ± 0.9% and 2.0 ± 0.8% of the total H I emission of NGC 891 and NGC 4565.

Keywords: Radio spectroscopy, Diffuse radiation, Extended radiation sources, H I line emission, Single-dish antennas, Circumgalactic medium, Extragalactic astronomy
Modeling the Transport Processes of a Pair of Solar Energetic Particle Events Observed by Parker Solar Probe Near Perihelion. We present model calculations of the transport processes of solar energetic particles in the corona and interplanetary medium for two events detected by Parker Solar Probe near its second perihelion on 2019 April 2 and April 4. In the 2019 April 2 event, the &lt;100 keV proton differential intensity measured by the Integrated Science Investigation of the Sun Low-Energy Energetic Particle instrument increased by more than a factor of 10 above the pre-event intensity, whereas the ∼1 MeV proton differential intensity detected by the High-Energy Energetic Particle Instrument did not show any intensity enhancement. In the 2019 April 4 event, the ∼1 MeV proton intensity showed an increase of more than a factor of 100 above the pre-event intensity, but the &lt;100 keV proton intensity enhancement was rather low and gradual. The observational fact that only the 2019 April 4 event displayed a high-energy intensity enhancement indicates that the associated acceleration process in the second event was more energetic than the first event. However, the gradual and low enhancement of the low-energy proton intensity in the second event is at odds with this scenario. In this paper, we investigate the injection and transport processes of protons in the corona and interplanetary magnetic fields with numerical model simulations. Our model calculations suggest that the gradual and low rise of the low-energy protons in the April 4 event was probably due to the different diffusion conditions in these two events and the fact that the spacecraft was moving away from the source region during these two events.

Keywords: Solar energetic particles
Multiwavelength Imaging and Spectral Analysis of Jet-like Phenomena in a Solar Active Region Using IRIS and AIA. High-resolution observations of dynamic phenomena give insights into the properties and processes that govern the low solar atmosphere. We present an analysis of jet-like phenomena emanating from a penumbral footpoint in active region (AR) 12192 using imaging and spectral observations from the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. These jets are associated with line-of-sight Doppler speeds of ±10-22 km s-1 and bright fronts that seem to move across the plane-of-sky at speeds of 23-130 km s-1. Such speeds are considerably higher than the expected sound speed in the chromosphere. The jets have signatures that are visible both in the cool and hot channels of IRIS and AIA. Each jet lasts on average 15 minutes and occurs 5-7 times over a period of 2 hr. Possible mechanisms to explain this phenomenon are suggested, the most likely of which involve p-mode or Alfvén wave shock trains impinging on the transition region and corona as a result of steepening photospheric wavefronts or gravity waves.

Keywords: Jets, Solar photosphere, Sunspots, Solar spicules, Solar active regions, Solar transition region, Shocks, Solar chromosphere
Hunting Distant BL Lacertae Objects with the Photometric Technique Using Swift and SARA. BL Lacertae objects represent a large fraction (22%) of γ-ray sources in the Third Fermi Large Area Telescope catalog (3FGL). Nearly half of the BL Lac object population remains without a redshift because of their featureless optical spectra. We aim to increase the number of BL Lac objects with a redshift measurement by using the photometric technique. For this work, we have used six Swift-UVOT filters and SDSS g', r', i', and z' optical filters mounted on the 0.65 m SARA-CTIO located in Chile and the 1.0 m SARA-ORM in the Canary Islands. A sample of 45 sources was selected from the 3FGL catalog for which photometry was performed in 10 optical and UV filters to obtain redshift measurements. We found three sources with z &gt; 1.3, while reliable upper limits have been provided for 17 sources. The results presented here bring the total number of high-z (z &gt; 1.3) BL Lac objects to 29.

Keywords: High energy astrophysics, Blazars, Active galaxies, Active galactic nuclei, High-redshift galaxies
Standing MHD Waves in a Magnetic Slab Embedded in an Asymmetric Magnetic Plasma Environment: Surface Waves. Building on a previous study that analyzed standing surface waves in magnetic slabs embedded in a non-magnetic external environment, in this study the model is generalized and external magnetic fields are added. The slab is assumed to be thin, with weak magnetic asymmetry. The frequencies of the standing harmonic modes are derived to leading order in the small quantities representing the thin slab width and the weak asymmetry. It is found that the frequencies are more sensitive to changes to the width of the slab than changes in the magnetic asymmetry. The frequency ratio of the first harmonic to the fundamental mode is derived, along with the amplitude difference between the two sides of the slab, as these may be observable quantities that can be compared with observational results and applied to carry out solar magnetoseismology.

Keywords: Solar atmosphere, Magnetohydrodynamics, Solar prominences, The Sun, Solar physics, Solar magnetic fields, Solar oscillations, Magnetic fields