adsabs/SciX_UAT_keywords huggingface dataset:
Enhanced Energy Conversion by Turbulence in Collisionless Magnetic Reconnection

Magnetic reconnection and turbulence are two of the most significant mechanisms for energy dissipation in collisionless plasma. The role of turbulence in magnetic reconnection poses an outstanding problem in astrophysics and plasma physics. It is still unclear whether turbulence can modify the reconnection process by enhancing the reconnection rate or energy conversion rate. In this study, utilizing unprecedented high-resolution data obtained from the Magnetospheric Multiscale spacecraft, we provide direct evidence that turbulence plays a vital role in promoting energy conversion during reconnection. We reached this conclusion by comparing magnetotail reconnection events with similar inflow Alfvén speed and plasma β but varying amplitudes of turbulence. The disparity in energy conversion was attributed to the strength of turbulence. Stronger turbulence generates more coherent structures with smaller spatial scales, which are pivotal contributors to energy conversion during reconnection. However, we find that turbulence has negligible impact on particle heating, but it does affect the ion bulk kinetic energy in these two events. These findings significantly advance our understanding of the relationship between turbulence and reconnection in astrophysical plasmas.

Keywords: interplanetary turbulence; solar magnetic reconnection; collisional broadening; space plasmas
Black Hole Growth, Baryon Lifting, Star Formation, and IllustrisTNG

Quenching of star formation in the central galaxies of cosmological halos is thought to result from energy released as gas accretes onto a supermassive black hole. The same energy source also appears to lower the central density and raise the cooling time of baryonic atmospheres in massive halos, thereby limiting both star formation and black hole growth, by lifting the baryons in those halos to greater altitudes. One predicted signature of that feedback mechanism is a nearly linear relationship between the central black hole's mass (M BH) and the original binding energy of the halo's baryons. We present the increasingly strong observational evidence supporting a such a relationship, showing that it extends up to halos of mass M halo ~ 1014 M ⊙. We then compare current observational constraints on the M BH-M halo relation with numerical simulations, finding that black hole masses in IllustrisTNG appear to exceed those constraints at M halo < 1013 M ⊙ and that black hole masses in EAGLE fall short of observations at M halo ~ 1014 M ⊙. A closer look at IllustrisTNG shows that quenching of star formation and suppression of black hole growth do indeed coincide with black hole energy input that lifts the halo's baryons. However, IllustrisTNG does not reproduce the observed M BH-M halo relation because its black holes gain mass primarily through accretion that does not contribute to baryon lifting. We suggest adjustments to some of the parameters in the IllustrisTNG feedback algorithm that may allow the resulting black hole masses to reflect the inherent links between black hole growth, baryon lifting, and star formation among the massive galaxies in those simulations.

Keywords: galaxy evolution; circumgalactic medium; supermassive black holes; active galaxies
Diversity of Early Kilonova with the Realistic Opacities of Highly Ionized Heavy Elements

We investigate early (t < 1 day) kilonova from a neutron star merger by deriving atomic opacities for all the elements from La to Ra (Z = 57–88) ionized to the states V–XI. The opacities at high temperatures for the elements with open f-shells (e.g., lanthanides) are exceptionally high, reaching at λ ≤ 1000 Å at T ∼ 70,000 K, whereas the opacities at the same temperature and wavelengths for the elements with open d-, p-, and s-shells reach , 0.1, and 0.01 cm2 g‑1, respectively. Using the new opacity data set, we derive early kilonovae for various compositions and density structures expected for neutron star merger ejecta. The bolometric luminosity of the lanthanide-rich ejecta shows distinct signatures and is fainter than that of the lanthanide-free ejecta. Early luminosity is suppressed by the presence of a thin outer layer, agreeing with the results of Kasen et al. and Banerjee et al. The early brightness in the Swift UVOT filters and in the optical g, r, i, and z filters for a source at 100 Mpc are about ∼22–19.5 and ∼21–20 mag, respectively, at t ∼ 0.1 day. Such kilonovae are ideal targets for the upcoming UV satellites, such as ULTRASAT, UVEX, and DORADO, and the upcoming surveys, e.g., the Vera Rubin Observatory. We suggest that the gray opacities that reproduce the bolometric light curves with and without lanthanides are ∼1–10 and ∼0.8 cm2 g‑1.

Keywords: neutron stars; nucleosynthesis; r-process; stellar atmospheric opacity; radiative transfer; gravitational waves
Modeling Linear Polarization of the Didymos–Dimorphos System before and after the DART Impact

We analyze the polarization observations of the Didymos–Dimorphos system before and after the impact by the NASA Double Asteroid Redirection Test spacecraft on Dimorphos. We fit empirical polarization phase curve models and statistically confirm the discovery by Gray et al. about the degree of linear polarization of the system decreasing on the impact and remaining altered for at least 30 days post-impact. With numerical simulations of particles in the geometric optics domain, we estimate the dominant size of the particles either in the regolith of Didymos and Dimorphos or in the impact-driven ejecta cloud to be several hundred micrometers. The observed change between the pre-impact and post-impact systems indicates either a decrease in average particle size of some tens of micrometers or a decreased level of space weathering.

Keywords: asteroid surfaces; near-earth objects; polarimetry
3D Radiative-transfer Simulations of the Ejecta Plume Anticipated from DART Impact

We present a modeling approach that allows the reconstruction of detailed images of the ejecta plume produced by the DART impact on asteroid Dimorphos. The approach is based on the 3D radiative-transfer technique and uses the publicly available HYPERION software package. The modeling automatically includes all interactions of light with the asteroid and ejecta plume, including transmission of the light through a hollow cone, reflection from the asteroid, and second transmission through the ejecta for each point within the ejecta plume and asteroid surface. The results of the modeling are the FITS images of the asteroid and ejecta as they will be seen by the LEIA camera on board LICIACube for any specific moments after impact. The parameters of the modeling are preimpact assumptions regarding Dimorphos' shape and composition, the presumed impact location, and the planned flyby trajectory of LICIACube. The results of the modeling show the readiness of our modeling tools to simulate the realistic ejecta plume after impact with the purpose to model the LICIACube images at different moments after impact and estimate the properties of the dust ejecta particles and the ejecta mass.

Keywords: impact phenomena; ejecta; space probes; asteroids
Revisiting the Lensed Fraction of High-redshift Quasars

The observed lensed fraction of high-redshift quasars (~0.2%) is significantly lower than previous theoretical predictions (≳4%). We revisit the lensed fraction of high-redshift quasars predicted by theoretical models, where we adopt recent measurements of galaxy velocity dispersion functions (VDFs) and explore a wide range of quasar luminosity function (QLF) parameters. We use both analytical methods and mock catalogs, which give consistent results. For ordinary QLF parameters and the depth of current high-redshift quasar surveys (m z ≲ 22), our model suggests a multiply imaged fraction of F multi ~ 0.4%-0.8%. The predicted lensed fraction is ~1%-6% for the brightest z s ~ 6 quasars (m z ≲ 19), depending on the QLF. The systematic uncertainties of the predicted lensed fraction in previous models can be as large as 2-4 times and are dominated by the VDF. Applying VDFs from recent measurements decreases the predicted lensed fraction and relieves the tension between observations and theoretical models. Given the depth of current imaging surveys, there are ~15 lensed quasars at z s > 5.5 detectable over the sky. Upcoming sky surveys like the Legacy Survey of Space and Time survey and the Euclid survey will find several tens of lensed quasars at this redshift range.

Keywords: quasars; strong gravitational lensing
Solar Energetic Particle Acceleration at a Spherical Shock with the Shock Normal Angle {\theta }_{{B}_{n}} Evolving in Space and Time

We present a 2D kinematic model to study the acceleration of solar energetic particles (SEPs) at a shock driven by a coronal mass ejection. The shock is assumed to be spherical about an origin that is offset from the center of the Sun. This leads to a spatial and temporal evolution of the angle between the magnetic field and the shock-normal direction (θ Bn ) as it propagates through the Parker spiral magnetic field from the lower corona to 1 au. We find that the high-energy SEP intensity varies significantly along the shock front due to the evolution of θ Bn . Generally, the west flank of the shock preferentially accelerates particles to high energies compared to the east flank and shock nose. This can be understood in terms of the rate of acceleration, which is higher at the west flank. Double power-law energy spectra are reproduced in our model as a consequence of the local acceleration and transport effects. These results will help us to better understand the evolution of SEP acceleration and provide new insights into large SEP events observed by multiple spacecraft, especially those close to the Sun, such as Parker Solar Probe and Solar Orbiter.

Keywords: solar energetic particles; solar coronal mass ejection shocks; interplanetary shocks
Premerger Sky Localization of Gravitational Waves from Binary Neutron Star Mergers Using Deep Learning

The simultaneous observation of gravitational waves (GW) and prompt electromagnetic counterparts from the merger of two neutron stars can help reveal the properties of extreme matter and gravity during and immediately after the final plunge. Rapid sky localization of these sources is crucial to facilitate such multimessenger observations. As GWs from binary neutron star (BNS) mergers can spend up to 10-15 minutes in the frequency bands of the detectors at design sensitivity, early-warning alerts and premerger sky localization can be achieved for sufficiently bright sources, as demonstrated in recent studies. In this work, we present premerger BNS sky localization results using GW-SkyLocator, a deep-learning model capable of inferring sky location posterior distributions of GW sources at orders of magnitude faster speeds than standard Markov Chain Monte Carlo methods. We test our model's performance on a catalog of simulated injections from Sachdev, recovered at 0-60 s before the merger, and obtain comparable sky localization areas to the rapid localization tool BAYESTAR. These results show the feasibility of our model for premerger sky localization and the possibility of follow-up observations for precursor emissions from BNS mergers.

Keywords: gravitational waves; gravitational wave astronomy; astronomical methods
TESS Asteroseismic Analysis of the Known Exoplanet Host Star HD 222076

The Transiting Exoplanet Survey Satellite (TESS) is an all-sky survey mission aiming to search for exoplanets that transit bright stars. The high-quality photometric data of TESS are excellent for the asteroseismic study of solar-like stars. In this work, we present an asteroseismic analysis of the red-giant star HD 222076 hosting a long-period (2.4 yr) giant planet discovered through radial velocities. Solar-like oscillations of HD 222076 are detected around 203 μHz by TESS for the first time. Asteroseismic modeling, using global asteroseismic parameters as inputs, yields a determination of the stellar mass ( ${M}_{\star }=1.12\pm 0.12\,{M}_{\odot }$ ), radius ( ${R}_{\star }=4.34\pm 0.21\,{R}_{\odot }$ ), and age (7.4 ± 2.7 Gyr), with precisions greatly improved from previous studies. The period spacing of the dipolar mixed modes extracted from the observed power spectrum reveals that the star is on the red-giant branch burning hydrogen in a shell surrounding the core. We find that the planet will not escape the tidal pull of the star and will be engulfed into it within about 800 Myr, before the tip of the red-giant branch is reached.

Keywords: asteroseismology; exoplanet systems
Constraints on the Intergalactic Magnetic Field Strength from γ-Ray Observations of GRB 221009A

Characteristics of the cascade gamma-ray signal resulting from very-high-energy gamma-ray sources, such as gamma-ray bursts, can be used to constrain the strength and structure of intergalactic magnetic fields (IGMFs). There has been a debate on whether GRB 190114C, the first gamma-ray burst with observed TeV photons, can constrain the IGMF. Recently, LHAASO detected the brightest-of-all-time GRB 221009A, which has much larger energy in the TeV band, and the spectrum extends to energy above 10 TeV, providing an unprecedented opportunity to study IGMF. We perform a Monte Carlo simulation of the cascade process with the public ELMAG code, considering the TeV data of GRB 221009A observed by LHAASO. By comparing the resulting cascade emission with the flux limit obtained from Fermi-LAT observations, we infer a limit of B ≥ 10-18.5 G for IGMF. Though this limit may not be as strong as the limit from blazars, it serves as an independent constraint on IGMF from a new class of TeV sources.

Keywords: gamma-ray bursts; high energy astrophysics; intergalactic medium; magnetic fields
Chains of Planets in Mean Motion Resonances Arising from Oligarchic Growth

Exoplanet systems with multiple planets in mean motion resonances have often been hailed as a signpost of disk-driven migration. Resonant chains like Kepler-223 and Kepler-80 consist of a trio of planets with the three-body resonant angle librating and/or with a two-body resonant angle librating for each pair. Here we investigate whether close-in super-Earths and mini-Neptunes forming in situ can lock into resonant chains due to dissipation from a depleted gas disk. We simulate the giant impact phase of planet formation, including eccentricity damping from a gaseous disk, followed by subsequent dynamical evolution over tens of millions of years. In a fraction of simulated systems, we find that planets naturally lock into resonant chains. These planets achieve a chain of near-integer period ratios during the gas-disk stage, experience eccentricity damping that captures them into resonance, stay in resonance as the gas disk dissipates, and avoid subsequent giant impacts, eccentricity excitation, and chaotic diffusion that would dislodge the planets from resonance. Disk conditions that enable planets to complete their formation during the gas-disk stage enable those planets to achieve tight period ratios ≤2 and, if they happen to be near-integer period ratios, lock into resonance. Using the weighting of different disk conditions deduced by MacDonald et al. and forward modeling Kepler selection effects, we find that our simulations of in situ formation via oligarchic growth lead to a rate of observable trios with integer period ratios and librating resonant angles comparable to observed Kepler systems.

Keywords: exoplanet formation; planet formation; protoplanetary disks; orbital evolution; orbital resonances; gravitational interaction; exoplanet dynamics; exoplanet astronomy; exoplanet systems
A Record of Water-ice Clouds at the Phoenix Landing Site Derived from Modeling MET Temperature Data

Water-ice clouds were frequently detected throughout the 151-sol Phoenix mission by the Phoenix lidar, providing insight into the Martian water cycle. However, the lidar could not be used continuously, and as such, the cloud data were temporally constrained to when observations were acquired. Here we reconstruct a record of water-ice clouds at the Phoenix landing site by examining the radiative contribution made by the clouds to the surface energy balance. This is accomplished by modeling the data from the 2 m MET air temperature sensor on board the lander. Clouds radiating from 0 and 30 W m-2 of energy toward the surface are consistent with the MET record over the course of the mission. The additional longwave flux at the surface induced a warming of the surface and near-surface temperatures, usually between 1-3 K; however, the clouds showed a high degree of sol-to-sol variability. This radiative analysis indicates that clouds were present much earlier in the mission than previously known, and cloud emission reached a maximum near sol 90, consistent with analyses of the annular cloud at the Phoenix landing site. The modeled flux from clouds was compared to the water-ice optical depth retrieved from the Phoenix lidar, showing that optically thicker clouds emitted more radiation toward the surface.

Keywords: planetary atmospheres; atmospheric clouds; planetary science; mars
Observational Evidence for Magnetic Field Amplification in SN 1006

We report the first observational evidence for magnetic field amplification in the northeast/southwest (NE/SW) shells of supernova remnant SN 1006, one of the most promising sites of cosmic ray acceleration. In previous studies, the strength of magnetic fields in these shells was estimated to be B SED ≃ 25 μG from the spectral energy distribution, where the synchrotron emission from relativistic electrons accounted for radio to X-rays, along with the inverse Compton emission extending from the GeV to TeV energy bands. However, the analysis of broadband radio data, ranging from 1.37 to 100 GHz, indicated that the radio spectrum steepened from α 1 = 0.52 ± 0.02 to α 2 = 1.34 ± 0.21 by Δα = 0.85 ± 0.21. This is naturally interpreted as a cooling break under a strong magnetic field of B brk ≥ 2 mG. Moreover, the high-resolution MeerKAT image indicated that the width of the radio NE/SW shells was broader than that of the X-ray shell by a factor of only 3‑20, as measured by Chandra. Such narrow radio shells can be naturally explained if the magnetic field responsible for the radio emissions is B R ≥ 2 mG. Assuming that the magnetic field is locally enhanced by a factor of approximately a = 100 along the NE/SW shells, we argue that the filling factor, which is the volume ratio of such a magnetically enhanced region to that of the entire shell, must be as low as approximately k = 2.5 × 10‑5.

Keywords: supernova remnants; magnetic fields; radio astronomy
A Candidate Location for Planet Nine from an Interstellar Meteoroid: The Messenger Hypothesis

The existence of a hypothetical Planet Nine lurking in the outer solar system has been invoked as a plausible explanation for the anomalous clustering in the orbits of trans-Neptunian objects. Here we propose that some meteoroids arriving at Earth could serve as messengers with the potential of revealing the presence of a hitherto undiscovered massive object. The peculiar meteor CNEOS 2014-01-08 recently put forward as the first interstellar meteor, might be one such messenger. The meteor radiant is in the maximum probability region calculated for the Planet Nine location in previous works. The odds of this coincidence being due to chance are ~1%. Furthermore, some statistical anomalies about CNEOS 2014-01-08 are resolved under the hypothesis that it was flung at Earth by a gravitational encounter. Integrating its trajectory backwards in time would then lead to the region of the sky where Planet Nine is more likely to reside. Based on the available data, we propose the region at coordinates R.A. 53.°0 ± 4.°3, decl. 9.°2 ± 1.°3 as a plausible candidate location for Planet Nine.

Keywords: small solar system bodies; solar system planets; meteor radiants; meteoroids; meteors; bolides
Climate of High-obliquity Exoterrestrial Planets with a Three-dimensional Cloud System Resolving Climate Model

Planetary climates are strongly affected by planetary orbital parameters such as obliquity, eccentricity, and precession. In exoplanetary systems, exoterrestrial planets should have various obliquities. High-obliquity planets would have extreme seasonal cycles due to the seasonal change of the distribution of the insolation. Here, we introduce the Non-hydrostatic ICosahedral Atmospheric Model (NICAM), a global cloud-resolving model, to investigate the climate of high-obliquity planets. This model can explicitly simulate a three-dimensional cloud distribution and vertical transports of water vapor. We simulated exoterrestrial climates with high resolution using the supercomputer FUGAKU. We assumed aqua-planet configurations with 1 bar of air as a background atmosphere, with four different obliquities (0°, 23.5°, 45°, and 60°). We ran two sets of simulations: (1) low resolution (~220 km mesh as the standard resolution of a general circulation model for exoplanetary science) with parameterization for cloud formation, and (2) high resolution (~14 km mesh) with an explicit cloud microphysics scheme. Results suggest that high-resolution simulations with an explicit treatment of cloud microphysics reveal warmer climates due to less low cloud fraction and a large amount of water vapor in the atmosphere. It implies that treatments of cloud-related processes lead to a difference between different resolutions in climatic regimes in cases with high obliquities.

Keywords: exoplanet atmospheres; planetary atmospheres
Two Numerical Methods for the 3D Anisotropic Propagation of Galactic Cosmic Rays

Conventional cosmic-ray propagation models usually assume an isotropic diffusion coefficient to account for the random deflection of cosmic rays by the turbulent interstellar magnetic field. Such models very successfully explain many observational phenomena related to the propagation of Galactic cosmic rays, such as broken power-law energy spectra, secondary-to-primary ratios, etc. However, the isotropic diffusion presupposition is facing severe challenges from recent observations. In particular, such observations on the large-scale anisotropy of TeV cosmic rays show that the dipole direction differs from the prediction of the conventional model. One possible reason is that the large-scale regular magnetic field, which leads to an anisotropic diffusion of cosmic rays, has not been included in the model provided by the public numerical packages. In this work, we propose two numerical schemes to solve the three-dimensional anisotropic transport equation: the pseudo-source method and Hundsdorfer-Verwer scheme. Both methods are verified by reproducing the measured B/C and proton spectrum and the radial variation of spectral index expected by former 2D simulation. As a demonstration of the prediction capability, dipole anisotropy is also calculated by a toy simulation with a rough magnetic field.

Keywords: cosmic ray astronomy; galactic cosmic rays; cosmic rays; supernova remnants; milky way magnetic fields