adsabs/SciX_UAT_keywords huggingface dataset:
Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Recently, transmission spectroscopy in the atmospheres of the TRAPPIST-1 planets revealed flat and featureless absorption spectra, which rule out cloud-free, hydrogen-dominated atmospheres. Earth-sized planets orbiting TRAPPIST-1 likely have either a clear or a cloudy/hazy, hydrogen-poor atmosphere. In this paper, we investigate whether a proposed formation scenario is consistent with expected atmospheric compositions of the TRAPPIST-1 planets. We examine the amount of hydrogen-rich gas that TRAPPIST-1-like planets accreted from the ambient disk until disk dispersal. Since TRAPPIST-1 planets are trapped into a resonant chain, we simulate disk gas accretion onto a migrating TRAPPIST-1-like planet. We find that the amount of accreted hydrogen-rich gas is as small as 10-2 wt% and 0.1 wt% for TRAPPIST-1 b and 1 c, 10-2 wt% for 1 d, 1 wt% for 1 e, a few wt% for 1 f and 1 g and 1 wt% for 1 h, respectively. We also calculate the long-term thermal evolution of TRAPPIST-1-like planets after disk dissipation and estimate the mass loss of their hydrogen-rich atmospheres driven by stellar X-ray and UV irradiation. We find that all the accreted hydrogen-rich atmospheres can be lost via hydrodynamic escape. Therefore, we conclude that TRAPPIST-1 planets should have no primordial hydrogen-rich gases but secondary atmospheres such as a Venus-like one and water vapor, if they currently retain atmospheres.

Keywords: exoplanet formation; exoplanet atmospheres; exoplanets; planet formation
Electrostatic Lofting Conditions for Supercharged Dust

Electrostatic dust lofting may be a common occurrence on small bodies in the solar system, whereby the upward electrostatic force on a grain is able to overcome the surface gravity and cohesion binding it to the surface. This electrostatic lofting may serve to redistribute and transport dust across the surface of these bodies to produce features such as dust ponds and lineations found on Eros, or even to rid bodies of small particles completely. Classical models, which distribute charge evenly across a dust grain, have historically predicted electric field strengths that are insufficient to loft dust. However, recent studies have developed grain-scale charging models that account for the buildup of charge in the microcavities of regolith and assume unequal distribution of charge on a dust grain. These models predict electric field strengths orders of magnitude larger than classical models, which may explain how electrostatic dust lofting occurs on small bodies. In this paper, we compare the grain-scale supercharging models developed by Zimmerman et al. and survey how the different parameters affect grain charging-namely, charge separation, grain size, and dielectric breakdown strength. Furthermore, we investigate how each of the charging models can be used to bound initial condition requirements such as charge and velocity for dust lofting to occur on these small bodies. Initial condition requirements are examined for a range of grain sizes, regolith cohesive strengths, and small body sizes.

Keywords: asteroids; asteroid surfaces; planetary surfaces; surface processes
The Next Generation Deep Extragalactic Exploratory Public Near-infrared Slitless Survey Epoch 1 (NGDEEP-NISS1): Extragalactic Star-formation and Active Galactic Nuclei at 0.5 < z < 3.6

The Next Generation Deep Extragalactic Exploratory Public (NGDEEP) survey program was designed specifically to include Near Infrared Slitless Spectroscopic observations (NGDEEP-NISS) to detect multiple emission lines in as many galaxies as possible and across a wide redshift range using the Near Infrared Imager and Slitless Spectrograph. We present early results obtained from the first set of observations (Epoch 1, 50% of the allocated orbits) of this program (NGDEEP-NISS1). Using a set of independently developed calibration files designed to deal with a complex combination of overlapping spectra, multiple position angles, and multiple cross filters and grisms, in conjunction with a robust and proven algorithm for quantifying contamination from overlapping dispersed spectra, NGDEEP-NISS1 has achieved a 3σ sensitivity limit of 2 × 10‑18 erg s‑1 cm‑2. We demonstrate the power of deep wide field slitless spectroscopy (WFSS) to characterize the star formation rates, and metallicity ([O III]/Hβ), and dust content, of galaxies at 1 < z < 3.5. The latter showing intriguing initial results on the applicability and assumptions made regarding the use of Case B recombination. Further, we identify the presence of active galactic nuclei and infer the mass of their supermassive black holes using broadened restframe Mg II and Hβ emission lines. The spectroscopic results are then compared with the physical properties of galaxies extrapolated from fitting spectral energy distribution models to photometry alone. The results clearly demonstrate the unique power and efficiency of WFSS at near-infrared wavelengths over other methods to determine the properties of galaxies across a broad range of redshifts.

Keywords: active galaxies; star formation
Discovery of State Transition Behaviors in PSR J1124-5916

With the 12 year long observations by Fermi-LAT, we discover two pairs of spin-down state transitions of PSR J1124-5916, making it the second young pulsar detected to have such behaviors. PSR J1124-5916 shows mainly two states according to its spin-down rate evolution, the normal spin-down state and the low spin-down state. In about 80% of the observation time, the pulsar is in the normal spin-down state, in which the spin-down rate decreases linearly and gives a braking index of 1.98 ± 0.04. The two transitions to the low spin-down state are in MJD 55183-55803 and MJD 56114-56398, respectively, with fractional amplitudes both ∼0.4%. No significant difference between the γ-ray profiles of the two spin-down states is detected, which is similar to PSR B0540-69, the other young pulsar with state transition detected.

Keywords: rotation powered pulsars; radio pulsars
Hα Emission and the Dependence of the Circumgalactic Cool Gas Fraction on Halo Mass

We continue our empirical study of the emission line flux originating in the cool (T ∼ 104 K) gas that populates the halos of galaxies and their environments. Specifically, we present results obtained for a sample of nearly half a million individual galaxies, groups, and clusters of galaxies, intersected by more than two million SDSS lines of sight at projected separations of up to a quarter of the virial radius. Adopting simple power-law relationships between the circumgalactic (CGM) cool gas fraction and either the halo or stellar mass, we present expressions for the CGM cool gas fraction as a function of either halo or stellar mass, {f}{{cool}}({M}h) =({0.23}-0.07+0.07) × {({M}h/{10}12{M}⊙ )}(-{0.40-0.07+0.06)} or {f}{{cool}}({M}\ast )=({0.28}-0.04+0.05) × {({M}\ast /{10}10.0{M}⊙ )}(-0.34+/- 0.04). Where we can compare, our results are consistent with previous constraints from absorption line studies, our own previous emission line work, and simulations. The cool gas can be the dominant baryonic CGM component, comprising a fraction as high as >90% of halo gaseous baryons, in low-mass halos, M h ∼ 1010.5 M ⊙, and a minor fraction, <5%, in groups and clusters, M h > 1014 M ⊙.

Keywords: galactic and extragalactic astronomy; extragalactic astronomy; intergalactic medium; intergalactic medium phases; cool intergalactic medium; intracluster medium; emission line galaxies
Systematic Study of AGN Clumpy Tori with Broadband X-Ray Spectroscopy: Updated Unified Picture of AGN Structure

We present the results of a systematic, broadband X-ray spectral analysis of nearby active galactic nuclei (AGNs) with the X-ray clumpy torus model (XCLUMPY). By adding 16 AGNs newly analyzed in this paper, we study a total of 28 AGNs, including unabsorbed and absorbed AGNs taken from Ichikawa et al. and García-Bernete et al. This is the largest sample whose X-ray and infrared spectra are analyzed by the clumpy torus models XCLUMPY and CLUMPY, respectively. The relation between the Eddington ratio and the torus covering factor determined from the X-ray torus parameters of each object follows the trend found by Ricci et al. based on a statistical analysis. We confirm the results by Tanimoto et al. that (1) the torus angular widths determined by the infrared data are larger than those by the X-ray data and (2) the ratios of hydrogen column density to V-band extinction (NH/AV) along the line of sight in obscured AGNs are similar to the Galactic value, on average. Unobscured AGNs show apparently smaller line-of-sight NH/AV ratios than the Galactic one. Our findings can be well explained by an updated unified picture of AGN structure including a dusty torus, dusty polar outflows, and dust-free gas, where the inclination determines the X-ray and optical classifications and observed torus properties in the X-ray and infrared bands.

Keywords: active galactic nuclei; astrophysical black holes; high energy astrophysics; seyfert galaxies; supermassive black holes; x-ray active galactic nuclei
The Location and Angle Distribution of Magnetic Reconnection in the Solar Corona

A major unresolved issue in solar physics is the nature of the reconnection events that may give rise to the extreme temperatures measured in the solar corona. In the nanoflare heating paradigm of coronal heating, localized reconnection converts magnetic energy into thermal energy, producing multithermal plasma in the corona. The properties of the corona produced by magnetic reconnection, however, depend on the details of the reconnection process. A significant challenge in understanding the details of reconnection in magnetohydrodynamic (MHD) models is that these models are frequently only able to tell us that reconnection has occurred, but there is significant difficulty in identifying precisely where and when it occurred. In order to properly understand the consequences of reconnection in MHD models, it is crucial to identify reconnecting field lines and where along the field lines reconnection occurs. In this work, we analyze a fully 3D MHD simulation of a realistic sunspot topology, driven by photospheric motions, and we present a model for identifying reconnecting field lines. We also present a proof-of-concept model for identifying the location of reconnection along the reconnecting field lines, and use that to measure the angle at which reconnection occurs in the simulation. We find evidence that magnetic reconnection occurs preferentially near field line footpoints, and discuss the implications of this for coronal heating models.

Keywords: magnetic fields; solar corona; solar magnetic reconnection; magnetohydrodynamics
Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs

Super-puffs-low-mass exoplanets with extremely low bulk density-are attractive targets for exploring their atmospheres and formation processes. Recent studies suggested that the large radii of super-puffs may be caused by atmospheric dust entrained in the escaping atmospheres. In this study, we investigate how the dust grows in escaping atmospheres and influences the transit radii using a microphysical model of grain growth. Collision growth is efficient in many cases, hindering the upward transport of dust via enhanced gravitational settling. We find that the dust abundance in the outflow hardly exceeds the Mach number at the dust production region. Thus, dust formed in the upper atmospheres, say at P ≲ 10-5 bar, is needed to launch a dusty outflow with a high dust abundance. With sufficiently high dust production altitudes and rates, the dusty outflow can enhance the observable radius by a factor of ~2 or even more. We suggest that photochemical haze is a promising candidate of high-altitude dust that can be entrained in the outflow. We also compute the synthetic transmission spectra of super-puff atmospheres and demonstrate that the dusty outflow produces a broad spectral slope and obscures molecular features, in agreement with featureless spectra recently reported for several super-puffs. Lastly, using an interior structure model, we suggest that the atmospheric dust could drastically enhance the observable radius only for planets in a narrow mass range of ~2-5 M⊕, in which the boil-off tends to cause total atmospheric loss. This may explain why super-puffs are uncommon despite the suggested universality of photochemical hazes.

Keywords: exoplanet atmospheres; exoplanet rings; transmission spectroscopy; atmospheric clouds
gyre_tides: Modeling Binary Tides within the GYRE Stellar Oscillation Code

We describe new functionality in the GYRE stellar oscillation code for modeling tides in binary systems. Using a multipolar expansion in space and a Fourier-series expansion in time, we decompose the tidal potential into a superposition of partial tidal potentials. The equations governing the small-amplitude response of a spherical star to an individual partial potential are the linear, non-radial, nonadiabatic oscillation equations with an extra inhomogeneous forcing term. We introduce a new executable, gyre_tides, that directly solves these equations within the GYRE numerical framework. Applying this to selected problems, we find general agreement with results in the published literature but also uncover some differences between our direct solution methodology and the modal decomposition approach adopted by many authors. In its present form gyre_tides can model equilibrium and dynamical tides of aligned binaries in which radiative diffusion dominates the tidal dissipation (typically, intermediate- and high-mass stars on the main sequence). Milestones for future development include incorporation of other dissipation processes, spin-orbit misalignment, and the Coriolis force arising from rotation.

Keywords: binary stars; tides; stellar oscillations; stellar evolution; astronomy software
Modulation of Galactic Cosmic Rays by Plasma Disturbances Propagating Through the Local Interstellar Medium in the Outer Heliosheath

The modulation of cosmic rays by a propagating plasma disturbance, a global merged interaction region (GMIR), in the heliosheath is simulated using a Vlasov-Fokker-Planck equation for the transport of energetic particles with significant anisotropy. The prescribed plasma structure of the GMIR contains a shock front and plasma rarefaction region behind the shock, which propagate through a simplified paramagnetic shielding model of the heliosheath. When a GMIR goes through the heliospheric magnetic field in the inner heliosheath, its modulation effects on cosmic rays are consistent with typical Forbush decreases. When a GMIR goes through the interstellar magnetic field in the outer heliosheath, only cosmic rays with large pitch angles with respect to the magnetic field vector (cosine values close to zero) are modulated by it. The difference is due to the very weak scattering of particles by the interstellar turbulence. Particles trapped in the rarefied magnetic field inside a GMIR suffer a significant amount of adiabatic cooling, which results in a considerable intensity decrease and a bidirectional anisotropy. The simulation result can be used to explain what Voyager 1 observed in the very local interstellar medium. Depending on the strength of plasma compression inside a GMIR, some cosmic rays may be accelerated, but the GMIR effect on the cosmic-ray intensity is much weaker than that due to adiabatic cooling because particles have only a brief interaction with a GMIR without trapping.

Keywords: forbush effect; cosmic rays
Spectral Observations and Modeling of a Solar White-light Flare Observed by CHASE

The heating mechanisms of solar white-light flares remain unclear. We present an X1.0 white-light flare on 2022 October 2 (SOL2022-10-02T20:25) observed by the Chinese Hα Solar Explorer that provides two-dimensional spectra in the visible light for the full solar disk with a seeing-free condition. The flare shows a prominent enhancement of ∼40% in the photospheric Fe I line at 6569.2 Å, and the nearby continuum also exhibits a maximum enhancement of ∼40%. For the continuum near the Fe I line at 6173 Å from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is enhanced up to ∼20%. At the white-light kernels, the Fe I line at 6569.2 Å has a symmetric Gaussian profile that is still in absorption and the Hα line at 6562.8 Å displays a very broad emission profile with a central reversal plus a red or blue asymmetry. The white-light kernels are cospatial with the microwave footpoint sources observed by the Expanded Owens Valley Solar Array and the time profile of the white-light emission matches that of the hard X-ray emission above 30 keV from the Gamma-ray Burst Monitor (GBM) on Fermi. These facts indicate that the white-light emission is qualitatively related to a nonthermal electron beam. We also perform a radiative hydrodynamic simulation with the electron-beam parameters constrained by the hard X-ray observations from Fermi/GBM. The result reveals that the white-light enhancement cannot be well explained by a pure electron-beam heating together with its induced radiative backwarming but may need additional heating sources such as Alfvén waves.

Keywords: solar activity; solar flares; solar flare spectra; solar photosphere; solar chromosphere; solar x-ray emission
Constraining the Jet Composition of GRB 221009A with the Prompt TeV Emission Limit

Recent LHAASO observations of the prompt emission phase of the brightest-of-all-time GRB 221009A imposes a stringent limit on the flux ratio between the TeV and MeV emissions, F TeV/F MeV ≤ 2 × 10-5, during the period 220-230 s after the trigger. This period covers the peak of the main MeV burst and is just before the TeV afterglow emerges. Within the framework of internal shocks, we study the internal γγ absorption in GRB 221009A by generating a set of synthetic bursts in a simulation that reproduces the observed feature of GRB 221009A. We find that the γγ absorption does not lead to an exponential cutoff, but rather a power-law spectrum, consistent with previous works. We further find that the attenuation due to γγ absorption alone cannot explain the flux limit ratio of GRB 221009A, suggesting a low ratio between synchrotron self-Compton (SSC) and synchrotron emission outputs. This requires the magnetic field energy density to be much larger than the synchrotron photon energy density so that the SSC flux is greatly suppressed. This indicates that the jet composition of GRB 221009A is likely Poynting flux dominated.

Keywords: gamma-ray bursts; high energy astrophysics; non-thermal radiation sources; radiative transfer
Low-frequency Waves Upstream of Quasi-parallel Shocks: Two-dimensional Hybrid Simulations

In this paper, we study low-frequency waves upstream of quasi-parallel shocks by using two-dimensional (2D) hybrid simulations. Simulation results show that reflected particles can backstream and form a superthermal particle component in plasmas in an area just before the shock front. The component interacts with the incident particles and can result in quasi-parallel and quasi-perpendicular fast magnetosonic waves with comparable wave amplitudes, and they have right-hand and linear polarization, respectively. Further upstream, after being scattered by these upstream waves, the backstreaming particles develop a shell-like velocity distribution so that similar waves can be driven by the free energy from this newly formed distribution, and in this area the quasi-perpendicular waves are dominant over the quasi-parallel ones. Linear theory confirms the generation of these two types of upstream waves.

Keywords: interplanetary shocks; shocks; planetary bow shocks
Simple Model for Temporal Variations of Hα Spectrum by an Eruptive Filament from a Superflare on a Solar-type Star

Flares are intense explosions on the solar and stellar surfaces, and solar flares are sometimes accompanied by filament or prominence eruptions. Recently, a large filament eruption associated with a superflare on a solar-type star EK Dra was discovered for the first time. The absorption of the Hα spectrum initially exhibited a blueshift with the velocity of 510 km s‑1, and decelerated in time probably due to gravity. Stellar coronal mass ejections (CMEs) were thought to occur, although the filament eruption did not exceed the escape velocity under the surface gravity. To investigate how such a filament eruption can occur and whether CMEs are associated with the filament eruption or not, we perform a one-dimensional hydrodynamic simulation of the flow along an expanding magnetic loop emulating a filament eruption under adiabatic and unsteady conditions. The loop configuration and expanding velocity normal to the loop are specified in the configuration parameters, and we calculate the line-of-sight velocity of the filament eruption using the velocities along and normal to the loop. We find that (i) the temporal variations of the Hα spectrum for EK Dra can be explained by a falling filament eruption in the loop with longer time and larger spatial scales than that of the Sun, and (ii) the stellar CMEs are also thought to be associated with the filament eruption from the superflare on EK Dra, because the rarefied loop unobserved in the Hα spectrum needs to expand faster than the escape velocity, whereas the observed filament eruption does not exceed the escape velocity.

Keywords: solar filament eruptions; solar coronal mass ejections; stellar coronal mass ejections; g dwarf stars; solar analogs; stellar flares; flare stars; solar flares
The 59Fe (n,γ) 60Fe Cross Section from the Surrogate Ratio Method and Its Effect on the 60Fe Nucleosynthesis

The long-lived 60Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction 59Fe(n,γ)60Fe on 59Fe (half-life = 44.5 days) is the key reaction for the production of 60Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 γ-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the 59Fe(n,γ)60Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5 ± 3.5 mb at kT = 30 keV and 13.4 ± 1.7 mb at kT = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of 60Fe from the 59Fe(n,γ)60Fe rate are at most 25%. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of 60Fe.

Keywords: nuclear physics; stellar nucleosynthesis; massive stars
All-sky Search for Transient Astrophysical Neutrino Emission with 10 Years of IceCube Cascade Events

Neutrino flares in the sky are searched for in data collected by IceCube between 2011 and 2021 May. This data set contains cascade-like events originating from charged-current electron neutrino and tau neutrino interactions and all-flavor neutral-current interactions. IceCube's previous all-sky searches for neutrino flares used data sets consisting of track-like events originating from charged-current muon neutrino interactions. The cascade data set is statistically independent of the track data sets, and while inferior in angular resolution, the low-background nature makes it competitive and complementary to previous searches. No statistically significant flare of neutrino emission was observed in an all-sky scan. Upper limits are calculated on neutrino flares of varying duration from 1 hr to 100 days. Furthermore, constraints on the contribution of these flares to the diffuse astrophysical neutrino flux are presented, showing that multiple unresolved transient sources may contribute to the diffuse astrophysical neutrino flux.

Keywords: neutrino astronomy; high energy astrophysics; transient sources