Sazuna/UAT_keywords huggingface dataset:
Turbulent Cascade and Energy Transfer Rate in a Solar Coronal Mass Ejection. Turbulence properties are examined before, during, and after a coronal mass ejection (CME) detected by the Wind spacecraft in 2012 July. The power-law scaling of the structure functions, providing information on the power spectral density and flatness of the velocity, magnetic field, and density fluctuations, were examined. The third-order moment scaling law for incompressible, isotropic magnetohydrodynamic turbulence was observed in the preceding and trailing solar wind, as well as in the CME sheath and magnetic cloud. This suggests that the turbulence could develop sufficiently after the shock, or that turbulence in the sheath and cloud regions was robustly preserved even during the mixing with the solar wind plasma. The turbulent energy transfer rate was thus evaluated in each of the regions. The CME sheath shows an increase of energy transfer rate, as expected from the lower level of Alfvénic fluctuations and suggesting the role of the shock-wind interaction as an additional source of energy for the turbulent cascade.

Keywords: Interplanetary turbulence, Solar wind, Solar coronal mass ejections
Evolution of Switchbacks in the Inner Heliosphere. We analyze magnetic field data from the first six encounters of Parker Solar Probe, three Helios fast streams and two Ulysses south polar passes covering heliocentric distances 0.1 ≲ R ≲ 3 au. We use this data set to statistically determine the evolution of switchbacks of different periods and amplitudes with distance from the Sun. We compare the radial evolution of magnetic field variances with that of the mean square amplitudes of switchbacks, and quantify the radial evolution of the cumulative counts of switchbacks per kilometer. We find that the amplitudes of switchbacks decrease faster than the overall turbulent fluctuations, in a way consistent with the radial decrease of the mean magnetic field. This could be the result of a saturation of amplitudes and may be a signature of decay processes of large amplitude Alfvénic fluctuations in the solar wind. We find that the evolution of switchback occurrence in the solar wind is scale dependent: the fraction of longer-duration switchbacks increases with radial distance, whereas it decreases for shorter switchbacks. This implies that switchback dynamics is a complex process involving both decay and in situ generation in the inner heliosphere. We confirm that switchbacks can be generated by the expansion, although other types of switchbacks generated closer to the Sun cannot be ruled out.

Keywords: Space plasmas, Heliosphere, Interplanetary turbulence, Solar wind, Alfven waves
Could Nearby Star-forming Galaxies Light Up the Pointlike Neutrino Sky?. Star-forming and starburst galaxies, which are well-known cosmic-ray reservoirs, are expected to emit gamma-rays and neutrinos predominantly via hadronic collisions. In this Letter, we analyze the 10 yr Fermi-LAT spectral energy distributions of 13 nearby galaxies by means of a physical model which accounts for high-energy proton transport in starburst nuclei and includes the contribution of primary and secondary electrons. In particular, we test the hypothesis that the observed gamma-ray fluxes are mostly due to star-forming activity, in agreement with the available star formation rates coming from IR and UV observations. Through this observation-based approach, we determine the most likely neutrino counterpart from star-forming and starburst galaxies and quantitatively assess the ability of current and upcoming neutrino telescopes to detect them as pointlike sources. Remarkably, we find that the cores of the Small Magellanic Cloud and the Circinus galaxy are potentially observable by KM3NeT/ARCA with 6 yr of observation. Moreover, most of the nearby galaxies are likely to be just a factor of a few below the KM3NeT and IceCube-Gen2 pointlike sensitivities. After investigating the prospects for detection of gamma-rays above TeV energies from these sources, we conclude that the joint observations of high-energy neutrinos and gamma-rays with upcoming telescopes will be an objective test for our emission model and may provide compelling evidence of star-forming activity as a tracer of neutrino production.

Keywords: Starburst galaxies, Neutrino telescopes, Star formation, Gamma-rays
Alfvén Speed Transition Zone in the Solar Corona. The Alfvén radius, rA, at which solar wind radial outflow speed exceeds the Alfvén wave speed, is an important parameter in understanding solar wind evolution in the extended corona. The mean solar wind angular momentum scales with ${r}_{A}^{2}$ in the axisymmetric steady-state approximation, so the Alfvén radius is often referenced in the study of solar wind corotation and dynamics. Alfvén wave speed is derived from the magnetic-field intensity and plasma mass density. In the inner coronal regions, these parameters were previously estimated using empirical models based on remote sensing observations or from inverse-square scaling of measurements at 1 au. Parker Solar Probe (PSP) orbital encounters now provide in situ coronal plasma measurements to determine Alfvén speeds within 30 solar radii of the heliocenter. We combined the PSP solar-wind speed measurements and calculated Alfvén speeds with an inner corona wind speed profile from remote sensing studies. The zone of super-Alfvénic speed cross over is estimated to occur at mean heliocentric distance of 17.9 ± 2.1 R⊙ for slow solar winds of the low heliolatitude corona in a near-minimum solar activity state. Our rA values constrain the angular momentum flux to a mean of 3.5 ± 1.01 × 1022 N m sr-1, reinforcing the recent PSP results by direct measurements of particle flows.

Keywords: Solar wind, Solar corona
Search for Line-like and Box-shaped Spectral Features from Nearby Galaxy Clusters with 11.4 Years of Fermi Large Area Telescope Data. Sharp spectral structures in the γ-ray band are an important dark matter (DM) signature. Previously, a tentative line feature at ~43 GeV was reported in 16 nearby galaxy clusters (GCls) with 7.1 yr of Fermi Large Area Telescope (LAT) data, whose test statistic (TS) value is ~16.7. In this work, we search for line signals and box-shaped structures using the stacked data from those 16 GCls with 11.4 yr of Fermi-LAT P8R3 data. There is still a hint at ~42 GeV, dominated by the radiation of the Virgo and Ophiuchus clusters. Though the TS value was high up to 21.2 in 2016 October, currently it has dropped to 13.1. Moreover, the TS value at ~42 GeV decreases to 2.4 when the EDISP2 data are excluded from the analysis. Consequently, we do not find any statistically significant line-like signal and then set up the 95% confidence level upper limits on the thermally averaged cross section of DM annihilating into double photons. The same line search has been carried out for an alternative GCl sample from the Two Micron All-Sky Survey, but no evidence has been found. We also search for box-shaped features in those 16 baseline GCls. No signal is found, and the corresponding upper limits on the annihilation cross section are given.

Keywords: Galaxy clusters, Baryonic dark matter, Gamma-ray lines
Profiles of Cosmic Filaments Since z = 4.0 in Cosmological Hydrodynamical Simulation. A large portion of the baryons at low redshifts are still missing from detection. Most of the missing baryons are believed to reside in large-scale cosmic filaments. Understanding the distribution of baryons in filaments is crucial to the search for missing baryons. We investigate the properties of cosmic filaments since z = 4.0 in a cosmological hydrodynamic simulation, focusing on the density and temperature profiles perpendicular to the filament spines. Our quantitative evaluation confirms the rapid growth of thick and prominent filaments after z = 2. We find that the local linear density of filaments shows a correlation with the local diameter since z = 4.0. The averaged density profiles of both dark matter and baryonic gas in filaments of different widths show self-similarity, and can be described by an isothermal single-beta model. The typical gas temperature increases as the filament width increases, and is hotter than 106 K for filaments with width Dfil ≳ 4.0 Mpc, which would be the optimal targets for the search of missing baryons via the thermal Sunyaev-Zel'dovich effect. The temperature rises significantly from the boundary to the inner core regime in filaments with Dfil ≳ 4.0 Mpc, probably due to heating by accretion shock, while the temperature rises modestly in filaments with Dfil &lt; 4.0 Mpc.

Keywords: Intergalactic medium, Hydrodynamical simulations, Cosmic web, Large-scale structure of the universe
DPNNet-2.0. I. Finding Hidden Planets from Simulated Images of Protoplanetary Disk Gaps. The observed substructures, like annular gaps, in dust emissions from protoplanetary disks are often interpreted as signatures of embedded planets. Fitting a model of planetary gaps to these observed features using customized simulations or empirical relations can reveal the characteristics of the hidden planets. However, customized fitting is often impractical owing to the increasing sample size and the complexity of disk-planet interaction. In this paper we introduce the architecture of DPNNet-2.0, second in the series after DPNNet, designed using a convolutional neural network (CNN, specifically ResNet50 here) for predicting exoplanet masses directly from simulated images of protoplanetary disks hosting a single planet. DPNNet-2.0 additionally consists of a multi-input framework that uses both a CNN and multilayer perceptron (a class of artificial neural network) for processing image and disk parameters simultaneously. This enables DPNNet-2.0 to be trained using images directly, with the added option of considering disk parameters (disk viscosities, disk temperatures, disk surface-density profiles, dust abundances, and particle Stokes numbers) generated from disk-planet hydrodynamic simulations as inputs. This work provides the required framework and is the first step toward the use of computer vision (implementing CNNs) to directly extract the mass of an exoplanet from planetary gaps observed in dust surface-density maps by telescopes such as the Atacama Large Millimeter/submillimeter Array.

Keywords: Exoplanet detection methods, Convolutional neural networks, Protoplanetary disks, Neural networks
Evolution of Elemental Abundances during B-Class Solar Flares: Soft X-Ray Spectral Measurements with Chandrayaan-2 XSM. The Solar X-ray Monitor (XSM) payload on board Chandrayaan-2 provides disk-integrated solar spectra in the 1-15 keV energy range with an energy resolution of 180 eV (at 5.9 keV) and a cadence of 1 s. During the period from 2019 September to 2020 May, covering the minimum of Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to B4.5. Using time-resolved spectroscopic analysis during these flares, we examined the evolution of temperature, emission measure, and absolute elemental abundances of four elements-Mg, Al, Si, and S. These are the first measurements of absolute abundances during such small flares and this study offers a unique insight into the evolution of absolute abundances as the flares evolve. Our results demonstrate that the abundances of these four elements decrease toward their photospheric values during the peak phase of the flares. During the decay phase, the abundances are observed to quickly return to their preflare coronal values. The depletion of elemental abundances during the flares is consistent with the standard flare model, suggesting the injection of fresh material into coronal loops as a result of chromospheric evaporation. To explain the quick recovery of the so-called coronal "First Ionization Potential bias" we propose two scenarios based on the Ponderomotive force model.

Keywords: Solar abundances, Solar x-ray flares
Neutrino-dominated Accretion Flows: A Second Nucleosynthesis Factory in Core-collapse Supernovae and Regulating the Iron Markets in Galaxies. Cosmic metals are widely believed to be produced by supernovae (SNe) and compact-object mergers. Here, we discuss the nucleosynthesis of neutrino-dominated accretion flows (NDAFs) with outflows in the centers of core-collapse SNe (CCSNe), and show that the outflows from NDAFs can have a significant contribution to the 56Ni abundances of faint explosions if the masses of the progenitor stars are within about 25-50 M⊙. Less-massive progenitor stars can produce more 56Ni than their more-massive counterparts in the NDAF outflow nucleosynthesis channel. Therefore, we find that the total (i.e., CCSNe and NDAF outflows) 56Ni mass per CCSN depends only weakly upon the mass of the progenitor star. In terms of metallicity evolution, the ratio of 56Fe (produced by the decay of 56Ni) mass to the initial total gas mass can increase by ~1.95 times if the upper limits of the nucleosynthesis yields from NDAF outflows and CCSNe are considered. Our results might have significant implications for the chemical evolution of the solar neighborhood, galaxies, and active galactic nuclei.

Keywords: Accretion, Black hole physics, Nucleosynthesis, Galaxy chemical evolution, Supernovae
The Atacama Cosmology Telescope: Microwave Intensity and Polarization Maps of the Galactic Center. We present arcminute-resolution intensity and polarization maps of the Galactic center made with the Atacama Cosmology Telescope. The maps cover a 32 deg2 field at 98, 150, and 224 GHz with ∣l∣ ≤ 4°, ∣b∣ ≤ 2°. We combine these data with Planck observations at similar frequencies to create coadded maps with increased sensitivity at large angular scales. With the coadded maps, we are able to resolve many known features of the Central Molecular Zone (CMZ) in both total intensity and polarization. We map the orientation of the plane-of-sky component of the Galactic magnetic field inferred from the polarization angle in the CMZ, finding significant changes in morphology in the three frequency bands as the underlying dominant emission mechanism changes from synchrotron to dust emission. Selected Galactic center sources, including Sgr A*, the Brick molecular cloud (G0.253+0.016), the Mouse pulsar wind nebula (G359.23-0.82), and the Tornado supernova remnant candidate (G357.7-0.1), are examined in detail. These data illustrate the potential for leveraging ground-based cosmic microwave background polarization experiments for Galactic science.

Keywords: Interstellar dust, Galactic center, Milky Way magnetic fields, Millimeter astronomy, Molecular clouds, Supernova remnants, Interstellar synchrotron emission, Magnetic fields
FORCAST Imaging of Two Small Nearby Clusters: The Coronet and B 59. We present mid-infrared imaging of two young clusters, the Coronet in the CrA cloud core and B 59 in the Pipe Nebula, using the FORCAST camera on the Stratospheric Observatory for Infrared Astronomy. We also analyze Herschel Space Observatory4 PACS and SPIRE images of the associated clouds. The two clusters are at similar, and very close, distances. Star formation is ongoing in the Coronet, which hosts at least one Class 0 source and several pre-stellar cores, which may collapse and form stars. The B 59 cluster is older, although it still has a few Class I sources, and is less compact. The CrA cloud has a diameter of ~0.16 pc, and we determine a dust temperature of 15.7 K and a star formation efficiency of ~27%. The B 59 core is approximately twice as large, with a dust temperature of ~11.4 K and a star formation efficiency of ~14%. We infer that the gas densities are much higher in the Coronet, which has also formed intermediate-mass stars, while B 59 has only formed low-mass stars.

Keywords: Star forming regions, Pre-main sequence stars, Star formation, Protoplanetary disks, Circumstellar disks, Protostars
Mixed Modes and Asteroseismic Surface Effects. I. Analytic Treatment. Normal-mode oscillation frequencies computed from stellar models differ from those that would be measured from stars with identical interior structures because of modeling errors in the near-surface layers. These frequency differences are referred to as the asteroseismic "surface term." The vast majority of solar-like oscillators that have been observed, and that are expected to be observed in the near future, are evolved stars that exhibit mixed modes. For these evolved stars, the inference of stellar properties from these mode frequencies has been shown to depend on how this surface term is corrected for. We show that existing parameterizations of the surface term account for mode mixing only to first order in perturbation theory, if at all, and therefore may not be adequate for evolved stars. Moreover, existing nonparametric treatments of the surface term do not account for mode mixing. We derive both a first-order construction and a more general approach for one particular class of nonparametric methods. We illustrate the limits of first-order approximations from both analytic considerations and using numerical injection-recovery tests on stellar models. First-order corrections for the surface term are strictly only applicable where the size of the surface term is much smaller than both the coupling strength between the mixed p and g modes, as well as the local g-mode spacing. Our more general matrix construction may be applied to evolved stars, where perturbation theory cannot be relied upon.

Keywords: Stellar oscillations, Computational methods, Asteroseismology, Theoretical techniques
Reverberation Mapping of Two Luminous Quasars: The Broad-line Region Structure and Black Hole Mass. We report the results of a multiyear spectroscopic and photometric monitoring campaign of two luminous quasars, PG 0923+201 and PG 1001+291, both located at the high-luminosity end of the broad-line region (BLR) size-luminosity relation with optical luminosities above 1045 erg s-1. PG 0923+201 is monitored for the first time, while PG 1001+291 was previously monitored but our campaign has a much longer temporal baseline. We detect time lags of variations of the broad Hβ, Hγ, and Fe II lines with respect to those of the 5100 Å continuum. The velocity-resolved delay map of Hβ in PG 0923+201 indicates a complicated structure with a mix of Keplerian disk-like motion and outflow, and the map of Hβ in PG 1001+291 shows a signature of Keplerian disk-like motion. Assuming a virial factor of fBLR = 1 and FWHM line widths, we measure the black hole mass to be ${118}_{-16}^{+11}\times {10}^{7}{M}_{\odot }$ for PG 0923+201 and ${3.33}_{-0.54}^{+0.62}\times {10}^{7}{M}_{\odot }$ for PG 1001+291. Their respective accretion rates are estimated to be ${0.21}_{-0.07}^{+0.06}\times {L}_{\mathrm{Edd}}\,{c}^{-2}$ and ${679}_{-227}^{+259}\times {L}_{\mathrm{Edd}}\,{c}^{-2}$ , indicating that PG 0923+201 is a sub-Eddington accretor and PG 1001+291 is a super-Eddington accretor. While the Hβ time lag of PG 0923+201 agrees with the size-luminosity relation, the time lag of PG 1001+291 shows a significant deviation, confirming that in high-luminosity active galactic nuclei (AGNs), the BLR size depends on both luminosity and Eddington ratio. Black hole mass estimates from single-AGN spectra will be overestimated at high luminosities and redshifts if this effect is not taken into account.

Keywords: Supermassive black holes, Reverberation mapping, Quasars
The Galaxy Progenitors of Stellar Streams around Milky Way-mass Galaxies in the FIRE Cosmological Simulations. Stellar streams record the accretion history of their host galaxy. We present a set of simulated streams from disrupted dwarf galaxies in 13 cosmological simulations of Milky Way (MW)-mass galaxies from the FIRE-2 suite at z = 0, including seven isolated MW-mass systems and six hosts resembling the MW-M31 pair. In total, we identify 106 simulated stellar streams, with no significant differences in the number of streams and the masses of their progenitors between the isolated and paired environments. We resolve simulated streams with stellar masses ranging from ~5 × 105 up to ~109 M⊙, similar to the mass range between the Orphan and Sagittarius streams in the MW. We confirm that present-day simulated satellite galaxies are good proxies for stellar stream progenitors, with similar properties including their stellar mass function, velocity dispersion, [Fe/H] and [α/H] evolution tracks, and orbital distribution with respect to the galactic disk plane. Each progenitor's lifetime is marked by several important timescales: its infall, star formation quenching, and stream formation times. We show that the ordering of these timescales is different between progenitors with stellar masses higher and lower than ~2 × 106 M⊙. Finally, we show that the main factor controlling the rate of phase mixing, and therefore the rate of fading, of tidal streams from satellite galaxies in MW-mass hosts is the nonadiabatic evolution of the host potential. Other factors commonly used to predict phase-mixing timescales, such as progenitor mass and orbital circularity, show virtually no correlation with the number of dynamical times required for a stream to become phase-mixed.

Keywords: Hydrodynamical simulations, Galaxy structure, Stellar streams
Insights from Snapshot Spectroscopic Radio Observations of a Weak Type I Solar Noise Storm. We present a high-fidelity snapshot spectroscopic radio imaging study of a weak type I solar noise storm that took place during an otherwise exceptionally quiet time. Using high-fidelity images from the Murchison Widefield Array, we track the observed morphology of the burst source for 70 minutes and identify multiple instances where its integrated flux density and area are strongly anticorrelated with each other. The type I radio emission is believed to arise due to electron beams energized during magnetic reconnection activity. The observed anticorrelation is interpreted as evidence for presence of MHD sausage wave modes in the magnetic loops and strands along which these electron beams are propagating. Our observations suggest that the sites of these small scale reconnections are distributed along the magnetic flux tube. We hypothesize that small scale reconnections produces electron beams which quickly get collisionally damped. Hence, the plasma emission produced by them span only a narrow bandwidth and the features seen even a few mehahertz apart must arise from independent electron beams.

Keywords: Solar coronal radio emission, Active solar corona, Solar radio flares, Solar coronal waves
A Possible Tidal Disruption Event Candidate in the Black Hole Binary System of OJ 287. The BL Lacertae OJ 287 is a supermassive black hole binary system with complex physics of its irregular flares. During 2016 October-2017 April, a surprising outburst in the X-ray, UV, and optical bands was detected, while no variability was seen in the γ-ray light curve. During the outburst, the X-ray light curves were dominated by the soft X-rays, whose peak in luminosity was ~1046 erg s-1-more than 10 times higher than the mean level before the outburst-and a "softer-when-brighter" phenomenon was exhibited. These above phenomena have been reported by some previous works. The hardness ratio showed negligible evolution with flare time and soft X-ray luminosity. Critically, the luminosity of the soft X-rays decayed following a power law of t-5/3, which occurs in most tidal disruption events (TDEs), and a similar trend can be seen in the UV and optical bands during the soft X-ray declining period. Helium and oxygen narrow emission lines are strengthened prominently in the optical spectra of postoutburst epochs, that could be attributed to the surrounding gas caused by TDE. We discuss three possible origins of the event, including the jet's precession, the aftereffects of the black hole-disk impaction, and the TDE. Our results show that the TDE is the more likely scenario to explain the outburst.

Keywords: Accretion, Black hole physics, Supermassive black holes, Blazars, Tidal disruption, X-ray bursts