adsabs/SciX_UAT_keywords huggingface dataset:
Three-dimensional Simulations of the Inhomogeneous Low Solar Wind

In the near future, the Parker Solar Probe will put theories about the dynamics and nature of the transition between the solar corona and the solar wind to stringent tests. The most popular mechanism aimed to explain the dynamics of the nascent solar wind, including its heating and acceleration, is magnetohydrodynamic (MHD) turbulence. Most of the previous models focused on nonlinear cascade induced by interactions of outgoing Alfvén waves and their reflections, ignoring effects that might be related to perpendicular structuring of the solar coronal plasma, despite overwhelming evidence for it. In this paper, for the first time, we analyze through 3D MHD numerical simulations the dynamics of the perpendicularly structured solar corona and solar wind, from the low corona to 15 R⊙. We find that background structuring has a strong effect on the evolution of MHD turbulence, on much faster timescales than in the perpendicularly homogeneous case. On timescales shorter than nonlinear times, linear effects related to phase mixing result in a 1/f perpendicular energy spectrum. As the turbulent cascade develops, we observe a perpendicular (parallel) energy spectrum with a power-law index of -3/2 or -5/3 (-2), a steeper perpendicular magnetic field than velocity spectrum, and a strong build-up of negative residual energy. We conclude that the turbulence is most probably generated by the self-cascade of the driven transverse kink waves, referred to previously as "uniturbulence," which might represent the dominant nonlinear energy cascade channel in the pristine solar wind.

Keywords: fast solar wind; interplanetary turbulence; magnetohydrodynamical simulations; solar coronal waves
Time Evolution of a System of Particles Obeying Coulomb's Law and the High-speed Rollover of Suprathermal Tails in the Solar Wind

In this article, we show through a series of rigorous mathematical steps, starting with Liouville's equation and solving it for the case of two protons using the method of characteristics, that a velocity distribution function, f(u), is formed that exhibits a power law, f ∝ uγ, where γ is -9/2, and an exponential-type rollover at large speeds, providing a potential explanation for the observations of suprathermal ions in the solar wind. The solution is valid for all times and all background conditions, though the power law does at some point merge with the core of the distribution. When it does so, a final distribution is found that agrees with overall energy conservation. Analytical approximations to the solution are discussed, along with explanations for the various phases that the solution undergoes.

Keywords: solar energetic particles
Coronal Conditions for the Occurrence of Type II Radio Bursts

Type II radio bursts are generally observed in association with flare-generated or coronal-mass-ejection-driven shock waves. The exact shock and coronal conditions necessary for the production of type II radio emission are still under debate. Shock waves are important for the acceleration of electrons necessary for the generation of the radio emission. Additionally, the shock geometry and closed field line topology, e.g., quasi-perpendicular shock regions or shocks interacting with streamers, play an important role for the production of the emission. In this study we perform a 3D reconstruction and modeling of a shock wave observed during the 2014 November 5 solar event. We determine the spatial and temporal evolution of the shock properties and examine the conditions responsible for the generation and evolution of type II radio emission. Our results suggest that the formation and evolution of a strong, supercritical, quasi-perpendicular shock wave interacting with a coronal streamer were responsible for producing type II radio emission. We find that the shock wave is subcritical before and supercritical after the start of the type II emission. The shock geometry is mostly quasi-perpendicular throughout the event. Our analysis shows that the radio emission is produced in regions where the supercritical shock develops with an oblique to quasi-perpendicular geometry.

Keywords: solar radio emission; solar coronal mass ejections; solar coronal mass ejection shocks
Shaping "Ears" in Planetary Nebulae by Early Jets

We conduct three-dimensional hydrodynamical numerical simulations of planetary nebula (PN) shaping and show that jets that precede the ejection of the main PN shell can form the morphological feature of ears. Ears are two opposite protrusions from the main nebula that are smaller than the main nebula and with a cross section that decreases monotonically from the base of an ear at the shell to its far end. Only a very small fraction of PNe have ears. The short-lived jets, about a year in the present simulations, interact with the regular asymptotic giant branch wind to form the ears, while the later blown dense wind forms the main PN dense shell. Namely, the jets are older than the main PN shell. We also find that for the jets to inflate ears they cannot be too energetic, cannot be too wide, and cannot be too slow. A flow structure where short-lived jets precede the main phase of nebula ejection by a few years or less can result from a system that enters a common envelope evolution. The low mass companion accretes mass through an accretion disk and launches jets just before it enters the envelope of the giant progenitor star of the PN. Shortly after that the companion enters the envelope and spirals-in to eject the envelope that forms the main PN shell.

Keywords: close binary stars; planetary nebulae; stellar jets
Bursty Star Formation Naturally Explains the Abundance of Bright Galaxies at Cosmic Dawn

Recent discoveries of a significant population of bright galaxies at cosmic dawn $\left(z\gtrsim 10\right)$ have enabled critical tests of cosmological galaxy formation models. In particular, the bright end of the galaxys' UV luminosity functions (UVLFs) appear higher than predicted by many models. Using approximately 25,000 galaxy snapshots at 8 ≤ z ≤ 12 in a suite of FIRE-2 cosmological "zoom-in" simulations from the Feedback in Realistic Environments (FIRE) project, we show that the observed abundance of UV-bright galaxies at cosmic dawn is reproduced in these simulations with a multichannel implementation of standard stellar feedback processes, without any fine-tuning. Notably, we find no need to invoke previously suggested modifications, such as a nonstandard cosmology, a top-heavy stellar initial mass function, or a strongly enhanced star formation efficiency. We contrast the UVLFs predicted by bursty star formation in these original simulations to those derived from star formation histories (SFHs) smoothed over prescribed timescales (e.g., 100 Myr). The comparison demonstrates that the strongly time-variable SFHs predicted by the FIRE simulations play a key role in correctly reproducing the observed, bright-end UVLFs at cosmic dawn: the bursty SFHs induce order-or-magnitude changes in the abundance of UV-bright (M UV ≲ -20) galaxies at z ≳ 10. The predicted bright-end UVLFs are consistent with both the spectroscopically confirmed population and the photometrically selected candidates. We also find good agreement between the predicted and observationally inferred integrated UV luminosity densities, which evolve more weakly with redshift in FIRE than suggested by some other models.

Keywords: galaxy formation; star formation; high-redshift galaxies
An Observed Transition of Galaxy Spins on Void Surfaces

In linear theory, the galaxy angular momentum vectors that originate from initial tidal interactions with surrounding matter distribution intrinsically develop perpendicular alignments with the directions of maximum matter compression, regardless of galaxy mass. In simulations, however, galaxy spins exhibit parallel alignments in the mass range lower than a certain threshold, which depends on redshift, web type, and background cosmology. We show that the observed three-dimensional spins of the spiral galaxies located on the void surfaces from the Sloan Digital Sky Survey indeed transit from perpendicular to parallel alignments with the directions toward the nearest void centers at the threshold zone, $9.51\leqslant \mathrm{log}[{M}_{\mathrm{th},\star }/(\,{h}^{-1}\,{M}_{\odot })]\leqslant 10.03$ . This study presents the first direct observational evidence for the occurrence of mass-dependent spin transition of real galaxies with respect to non-filamentary structures of the cosmic web, opening a way to constrain the initial conditions of the early universe by measuring the spin transition threshold.

Keywords: cosmology; large-scale structure of the universe
Validation of TOI-1221 b: A Warm Sub-Neptune Exhibiting Transit Timing Variations around a Sun-like Star

We present a validation of a long-period ( ${91.68278}_{-0.00041}^{+0.00032}$ days) transiting sub-Neptune planet, TOI-1221 b (TIC 349095149.01), around a Sun-like (m V = 10.5) star. This is one of the few known exoplanets with a period >50 days, and belongs to the even smaller subset of which have bright enough hosts for detailed spectroscopic follow-up. We combine Transiting Exoplanet Survey Satellite light curves and ground-based time-series photometry from the Perth Exoplanet Survey Telescope (0.3 m) and Las Cumbres Observatory global telescope network (1.0 m) to analyze the transit signals and rule out nearby stars as potential false-positive sources. High-contrast imaging from the Southern Astrophysical Research Telescope and Gemini/Zorro rule out nearby stellar contaminants. Reconnaissance spectroscopy from CHIRON sets a planetary scale upper mass limit on the transiting object (1.1 and 3.5 M Jup at 1σ and 3σ, respectively) and shows no sign of a spectroscopic binary companion. We determine a planetary radius of ${R}_{{\rm{p}}}={2.91}_{-0.12}^{+0.13}{R}_{\oplus }$ , placing it in the sub-Neptune regime. With a stellar insolation of $S={6.06}_{-0.77}^{+0.85}\ {S}_{\oplus }$ , we calculate a moderate equilibrium temperature of T eq = 440 K, assuming no albedo and perfect heat redistribution. We find a false-positive probability from the TRICERATOPS tool of FPP = 0.0014 ± 0.0003 as well as other qualitative and quantitative evidence to support the statistical validation of TOI-1221 b. We find significant evidence (>5σ) of oscillatory transit timing variations, likely indicative of an additional nontransiting planet.

Keywords: exoplanet astronomy; exoplanet systems; exoplanet dynamics
Cloudy in the Microcalorimeter Era: Improved Energies for Kα Transitions

X-ray missions with microcalorimeter technology will resolve spectral features with unprecedented detail. In this work, we improve the H-like Kα energies for elements between 6 ≤ Z ≤ 30 for the release version of the spectral simulation code Cloudy to match laboratory energies. We update the ionization potential (Iion) for these elements and add a fourth-order polynomial to the level energy difference. This brings the release version of Cloudy into a near-perfect agreement with NIST. The updated energies are ∼15-4000 times more precise than that of the current release version of Cloudy (C17.02). These new changes will be a part of the next update to the release version, C17.03.

Keywords: high resolution spectroscopy; x-ray astronomy
Gas Disk Sizes from CO Line Observations: A Test of Angular Momentum Evolution

The size of a disk encodes important information about its evolution. Combining new Submillimeter Array observations with archival Atacama Large Millimeter/submillimeter Array data, we analyze millimeter continuum and CO emission line sizes for a sample of 44 protoplanetary disks around stars with masses of 0.15-2 M ⊙ in several nearby star-forming regions. Sizes measured from 12CO line emission span from 50 to 1000 au. This range could be explained by viscous evolution models with different α values (mostly of 10-4-10-3) and/or a spread of initial conditions. The CO sizes for most disks are also consistent with MHD wind models that directly remove disk angular momentum, but very large initial disk sizes would be required to account for the very extended CO disks in the sample. As no CO size evolution is observed across stellar ages of 0.5-20 Myr in this sample, determining the dominant mechanism of disk evolution will require a more complete sample for both younger and more evolved systems. We find that the CO emission is universally more extended than the continuum emission by an average factor of 2.9 ± 1.2. The ratio of the CO to continuum sizes does not show any trend with stellar mass, millimeter continuum luminosity, or the properties of substructures. The GO Tau disk has the most extended CO emission in this sample, with an extreme CO-to-continuum size ratio of 7.6. Seven additional disks in the sample show high size ratios (≳4) that we interpret as clear signs of substantial radial drift.

Keywords: protoplanetary disks; submillimeter astronomy; pre-main sequence stars
Friends and Foes: Conditional Occurrence Rates of Exoplanet Companions and Their Impact on Radial Velocity Follow-up Surveys

Population studies of Kepler's multiplanet systems have revealed a surprising degree of structure in their underlying architectures. Information from a detected transiting planet can be combined with a population model to make predictions about the presence and properties of additional planets in the system. Using a statistical model for the distribution of planetary systems, we compute the conditional occurrence of planets as a function of the period and radius of Kepler-detectable planets. About half (0.52 ± 0.03) of the time, the detected planet is not the planet with the largest semi-amplitude (K) in the system, so efforts to measure the mass of the transiting planet with radial velocity (RV) follow up will have to contend with additional planetary signals in the data. We simulate RV observations to show that assuming a single-planet model to measure the K of the transiting planet often requires significantly more observations than in the ideal case with no additional planets, due to systematic errors from unseen planet companions. Our results show that planets around 10 day periods with K close to the single-measurement RV precision (σ1,obs) typically require ~100 observations to measure their K to within 20% error. For a next generation RV instrument achieving σ1,obs = 10 cm s-1, about ~200 (600) observations are needed to measure the K of a transiting Venus in a Kepler-like system to better than 20% (10%) error, which is ~2.3 times as many as would be necessary for a Venus without any planetary companions.

Keywords: exoplanet detection methods; exoplanet catalogs; exoplanet systems; planet hosting stars; radial velocity; extrasolar rocky planets; exoplanets; solar system planets; computational methods
Modeling the Propagation of Slow Magnetoacoustic Waves in a Multistranded Coronal Loop

We study the propagation properties of slow magnetoacoustic waves in a multithermal coronal loop using a 3D MHD model, for the first time. A bundle of 33 vertical cylinders, each of 100 km radius, randomly distributed over a circular region of radius 1 Mm, is considered to represent the coronal loop. The slow waves are driven by perturbing the vertical velocity (v z ) at the base of the loop. We apply forward modeling to the simulation results to generate synthetic images in the coronal channels of the Solar Dynamics Observatory/Atmospheric Imaging Assembly. Furthermore, we add appropriate data noise to enable direct comparison with the real observations. It is found that the synthetic images at the instrument resolution show noncospatial features in different temperature channels in agreement with previous observations. Time–distance maps are constructed from the synthetic data to study the propagation properties. The results indicate that the oscillations are only visible in specific channels, depending on the temperature range of the plasma existing within the loop. Additionally, the propagation speed of slow waves is also found to be sensitive to the available temperature range. Overall, we propose that the cross-field thermal properties of coronal structures can be inferred using a combination of numerical simulations and observations of slow magnetoacoustic waves.

Keywords: magnetohydrodynamical simulations; solar coronal heating; solar coronal loops; solar coronal waves
Quasar Factor Analysis-An Unsupervised and Probabilistic Quasar Continuum Prediction Algorithm with Latent Factor Analysis

Since their first discovery, quasars have been essential probes of the distant Universe. However, due to our limited knowledge of its nature, predicting the intrinsic quasar continua has bottlenecked their usage. Existing methods of quasar continuum recovery often rely on a limited number of high-quality quasar spectra, which might not capture the full diversity of the quasar population. In this study, we propose an unsupervised probabilistic model, quasar factor analysis (QFA), which combines factor analysis with physical priors of the intergalactic medium to overcome these limitations. QFA captures the posterior distribution of quasar continua through generatively modeling quasar spectra. We demonstrate that QFA can achieve the state-of-the-art performance, ~2% relative error, for continuum prediction in the Lyα forest region compared to previous methods. We further fit 90,678 2 < z < 3.5, signal-to-noise ratio >2 quasar spectra from Sloan Digital Sky Survey Data Release 16 and found that for ~30% quasar spectra where the continua were ill-determined with previous methods, QFA yields visually more plausible continua. QFA also attains ≲1% error in the 1D Lyα power spectrum measurements at z ~ 3 and ~4% in z ~ 2.4. In addition, QFA determines latent factors representing more physical motivation than principal component analysis. We investigate the evolution of the latent factors and report no significant redshift or luminosity dependency except for the Baldwin effect. The generative nature of QFA also enables outlier detection robustly; we showed that QFA is effective in selecting outlying quasar spectra, including damped Lyα systems and potential Type II quasar spectra.

Keywords: quasars; active galactic nuclei; supermassive black holes; intergalactic medium; bayesian statistics; posterior distribution; lyman alpha forest
Probing the Heart of Active Narrow-line Seyfert 1 Galaxies with VERA Wideband Polarimetry

We explored the parsec-scale nuclear regions of a sample of radio-loud narrow-line Seyfert 1 galaxies (NLSy1s) using the VLBI Exploration of Radio Astrometry wideband (at a recording rate of 16 Gbps) polarimetry at 22 and 43 GHz. Our targets include 1H 0323+342, SBS 0846+513, PMN J0948+0022, 1219+044, PKS 1502+036, and TXS 2116-077, which are all known to exhibit γ-ray emission indicative of possessing highly beamed jets similar to blazars. For the first time, we unambiguously detected Faraday rotation toward the parsec-scale radio core of NLSy1s, with a median observed core rotation measure (RM) of 2.7 × 103 rad m-2 (or 6.3 × 103 rad m-2 for redshift-corrected). This level of RM magnitude is significantly larger than those seen in the core of BL Lacertae objects (BLOs; a dominant subclass of blazars), suggesting that the nuclear environment of NLSy1s is more gas-rich than that in BLOs. Interestingly, the observed parsec-scale polarimetric properties of NLSy1s (low core fractional polarization, large core RM and jet-EVPA misalignment) are rather similar to those of flat-spectrum radio quasars (FSRQs). Our results are in accordance with the scenario that NLSy1s are in an early stage of active galactic nucleus evolution with their central black hole masses being smaller than those of more evolved FSRQs.

Keywords: very long baseline interferometry; seyfert galaxies; polarimetry; radio jets; active galactic nuclei
Relativistic Shear Boundary Layer and the Gamma-Ray Emission of GW170817

We present an analysis of the radiation characteristics of kinetic shear boundary layers created by relativistic plasma jets. Using a model of electromagnetic field data based on particle-in-cell simulations of an electron-ion plasma, we solve the motion of individual test electrons and compute their instantaneous radiated power and peak frequency. By analyzing a large number of test electrons in this manner, we find two distinct electron populations present around the shear boundary layer. The most highly radiative electrons execute looping motion due to crossed electric and magnetic fields as they are accelerated along the bulk flow of the jet, and eventually cross the shear boundary interface at steep angles. Electrons that never cross the shear boundary interface radiate much less energy as a group. Summing over all of the highly radiative electrons, we compute the distribution of the total radiated energy as a function of the angle relative to the bulk flow. This result has important potential implications for the observed radiation output of short gamma-ray bursts viewed at large angles from the jet axis, such as the neutron star merger event GW170817/GRB 170817A.

Keywords: plasma astrophysics; gamma-ray bursts; relativistic jets
Fine Structures of the Inner Solar Corona and the Associated Magnetic Topology

We present the fine structure of the inner solar corona between 1.65 and 3.0 solar radii as revealed by the STEREO-A COR1 white-light coronagraph from 2008 June 20 to July 31. The COR1 imaging data were wavelet processed to enhance the intensity contrast of coronal features. The constructed limb synoptic maps at a range of altitudes show the evolution in time and altitude of these fine structures within the streamer belt, and equatorial and polar coronal holes during this period near the solar minimum. Distinct streamer-stalk structures are seen embedded within a diffuse background of the helmet streamer belt, which are preserved as they extend to higher heights. Pseudostreamers are also seen as multiple stalk structures, which also continue to higher heights. Various polar plume structures are seen to last from hours to days. Similar plume structures are also seen within the corona subtended by equatorial coronal holes. We compare the COR1 maps to that of the magnetic topology revealed by the modeled squashing factors, and discuss the relation between the two types of maps and its implications in the context of solar wind formation.

Keywords: solar corona
Non-confirmation of the Astrometric Binary Candidate HD 113283 Using FEROS Radial Velocities

We present fifteen radial velocity (RV) measurements taken with FEROS for the astrometric binary candidate HD 113283 analyzed with the "exoplanet pipeline" and published in the nss_two_body_orbit table of Gaia Data Release 3. We have performed a periodogram analysis on the RVs and found no evidence of the stellar companion of mass m 2 > 0.15M ⊙. We discuss indications for the likely spurious astrometric two-body solution based on the Gaia products, including the comparably low significance, the small reduction of the astrometric excess noise after applying the two-body solution, inconsistent with the provided orbital solution, and the proximity of the orbital period to periods of known spurious solutions caused by Gaia's scanning law. We aim to contribute toward a refined solution filtering of the Gaia two-body solutions.

Keywords: binary stars; astrometric binary stars; gaia; radial velocity; astrometry; high resolution spectroscopy; spectroscopic binary stars