adsabs/SciX_UAT_keywords huggingface dataset:
The K2-3 System Revisited: Testing Photoevaporation and Core-powered Mass Loss with Three Small Planets Spanning the Radius Valley

Multiplanet systems orbiting M dwarfs provide valuable tests of theories of small-planet formation and evolution. K2-3 is an early M dwarf hosting three small exoplanets (1.5-2.0 R ⊕) at distances of 0.07-0.20 au. We measure the high-energy spectrum of K2-3 with HST/COS and XMM-Newton and use empirically driven estimates of Lyα and extreme-ultraviolet flux. We use EXOFASTv2 to jointly fit radial velocity, transit, and spectral energy distribution data. This constrains the K2-3 planet radii to 4% uncertainty and the masses of K2-3b and c to 13% and 30%, respectively; K2-3d is not detected in radial velocity measurements. K2-3b and c are consistent with rocky cores surrounded by solar composition envelopes (mass fractions of ${0.36}_{-0.11}^{+0.14} \% $ and ${0.07}_{-0.05}^{+0.09} \% $ ), H2O envelopes ( ${55}_{-12}^{+14} \% $ and ${16}_{-10}^{+17} \% $ ), or a mixture of both. However, based on the high-energy output and estimated age of K2-3, it is unlikely that K2-3b and c retain solar composition atmospheres. We pass the planet parameters and high-energy stellar spectrum to atmospheric models. Dialing the high-energy spectrum up and down by a factor of 10 produces significant changes in trace molecule abundances, but not at a level detectable with transmission spectroscopy. Though the K2-3 planets span the small-planet radius valley, the observed system architecture cannot be readily explained by photoevaporation or core-powered mass loss. We instead propose that (1) the K2-3 planets are all volatile-rich, with K2-3d having a lower density than typical of super-Earths, and/or (2) the K2-3 planet architecture results from stochastic processes such as planet formation, planet migration, and impact erosion.

Keywords: exoplanet evolution; exoplanet atmospheric composition; exoplanet systems; m dwarf stars; low mass stars; hubble space telescope; ultraviolet astronomy; x-ray astronomy
Constraining the Existence of Axion Clouds in M87* with Closure Trace Analyses

Black holes can amplify incoming bosonic waves via rotational superradiance, inducing bound states of ultralight bosons around them. This phenomenon has the potential to confine the parameter spaces of new bosons. Axions and axion-like particles (ALPs) are candidate beyond-standard-model particles that can form such clouds around supermassive black holes (SMBHs) and impact the polarization signal in a similar fashion to Faraday rotation via axion–photon coupling. Prior efforts have used polarized images from the Event Horizon Telescope (EHT) M87 2017 observations to limit the dimensionless axion–photon coupling to previously unexplored regions. However, with the novel calibration-insensitive quantities, closure traces, and conjugate closure trace products, it is possible to constrain the existence of axion clouds while avoiding the dominant sources of systematic uncertainties, e.g., station gains and polarization leakages. We utilize a simple geometric model for the polarization map of M87* to fit the model parameters with both simulated and real data sets and reach a comparable level of constraint in the accuracy with which an axion cloud may be excluded in M87. Future applications of our approach include subsequent M87* and Sgr A* observations by EHT and the next-generation EHT that are expected to produce stronger constraints across a wider range of axion and ALP masses. Because it does not require imaging, closure trace analyses may be applied to target active galactic nuclei for which imaging is marginal, extending the number of SMBHs from which axion limits may be obtained significantly.

Keywords: supermassive black holes; markov chain monte carlo; polarimetry; very long baseline interferometry; radio astronomy; particle astrophysics; penrose process; ergosphere
Survey of Bare Active Galactic Nuclei in the Local Universe (z < 0.2). I. On the Origin of Soft Excess

We analyze a sample of 21 "bare" Seyfert 1 active galactic nuclei, a subclass of Seyfert 1 galaxies, with intrinsic absorption N H ~ 1020 cm-2, in the local Universe (z < 0.2) using XMM-Newton and Swift/XRT observations. The luminosities of the primary continuum, the X-ray emission in the 3-10 keV energy range, and the soft excess-the excess emission that appears above the low-energy extrapolation of the power-law fit of 3-10 keV X-ray spectra-are calculated. Our spectral analysis reveals that the long-term intrinsic luminosities of the soft excess and the primary continuum are tightly correlated $({L}_{\mathrm{PC}}\propto {L}_{\mathrm{SE}}^{1.1\pm 0.04})$ . We also found that the luminosities are correlated for each source. This result suggests that both the primary continuum and soft excess emissions exhibit a dependency on the accretion rate in a similar way.

Keywords: seyfert galaxies; x-ray active galactic nuclei; black hole physics; accretion
Low-frequency Gravitational-wave Memories from Gamma-Ray Burst Afterglows with Energy Injections

Ultrarelativistic gamma-ray burst (GRB) jets are strong gravitational-wave (GW) sources with memory-type signals. The plateau (or shallow decay) phases driven by the energy injection may appear in the early X-ray afterglows of GRBs. In this paper, we investigate GW signals as well as X-ray afterglow emissions in the framework of GRB jets with energy injections, and both short- and long-duration GRBs are considered. We find that, regardless of the case, and because of the antibeaming and time delay effects, a rising slope that emerges in the waveform of the GW signal, due to the energy injection, lags far behind the energy ejection, and the typical frequencies of the characteristic amplitudes fall within a low-frequency region of ~10-4-10-6 Hz; we also consider that the GW memories triggered by the GRB jets with energy injection have previously not been accounted for and that nearby GRBs with strong energy injections may disturb the measurement of the stochastic GW background. Such GW memory detection would provide a direct test for models of energy injection in the scenario of GRB jets.

Keywords: gamma-ray bursts; relativistic jets; shocks; gravitational waves
East-West Proton Flux Anisotropy Observed with the PAMELA Mission

We present a study of the east-west anisotropy of trapped-proton fluxes in low-Earth orbit based on the measurements of the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment. The differential intensities of eastward- and westward-traveling protons detected in the South Atlantic Anomaly region were estimated as a function of equatorial pitch angle and drift shell, for six energy bins between 80 MeV and 2 GeV. We found that, as a consequence of the strong atmospheric gradient coupled with the large gyroradius in this energy range, the intensities of eastward fluxes exceed those of westward fluxes by a factor of ~10-20. However, the reported directional asymmetry also depends on the sign of the local flux gradient, resulting in more intense westward fluxes beyond the radial distances where the inner belt peaks. PAMELA observations can be used to improve the description of the near-Earth radiation environment at lowest altitudes and highest trapping energies, where current theoretical and empirical models are affected by the largest uncertainties.

Keywords: cosmic rays; van allen radiation belts
Fermi-GBM Observation of GRB 090717034: χ 2 Test Confirms Evidence of Gravitational Lensing by a Supermassive Black Hole with a Million Solar Mass

Gravitational lensing of gamma-ray bursts (GRBs) can provide an opportunity to probe the massive compact objects in the universe at different redshifts. We have discovered two consecutive pulses in the light curve of GRB 090717034, with the same temporal profile and different count rate, separated by a time interval, which is identified as a gravitationally lensed candidate in the Fermi-GBM GRB catalog. Here, we use the χ 2 minimization method to investigate the similarity of the temporal profile variability of the two pulses as a gravitationally lensed GRB candidate. We find the magnification factor and the time delay between two pulses to minimize the χ 2 function. Then, we perform a Monte Carlo simulation on a sample of mock lensed GRBs and compare the χ 2 of the lensed GRB candidate with the simulation, which confirms this candidate with 1σ confidence level. Assuming that GRB 090717034 is lensed by a pointlike object, the redshifted lens mass is about M L (1 + z) = (4.839 ± 1.148) × 106 M ⊙. The lens of this GRB is a candidate for a supermassive black hole along the line of sight to the GRB.

Keywords: gamma-ray bursts; gravitational lensing; black holes
A Comparative Analysis to Deal with Missing Spectral Information Caused by RFI in Cosmological H I 21 cm Observations

We investigate the effect of radio-frequency interference (RFI) excision in estimating the cosmological H I 21 cm power spectrum. Flagging of RFI-contaminated channels results in a nonuniform sampling of the instrumental bandpass response. Hence, the Fourier transformation of visibilities from frequency to delay domain contaminates the higher foreground-free delay modes, and separating the spectrally fluctuating H I signal from spectrally smooth foregrounds becomes challenging. We have done a comparative analysis between two algorithms, one-dimensional CLEAN and least-squares spectral analysis (LSSA), which have been used widely to solve this issue in the literature. We test these algorithms using the simulated SKA-1 Low observations in the presence of different RFI flagging scenarios. We find that, in the presence of random flagging of data, both algorithms perform well and can mitigate the foreground leakage issue. But CLEAN fails to restrict the foreground leakage in the presence of periodic and periodic plus broadband RFI flagging and gives an extra bias to the estimated power spectrum. However, LSSA can restrict the foreground leakage for these RFI flagging scenarios and gives an unbiased estimate of the H I 21 cm power spectrum. We have also applied these algorithms to observations with the upgraded GMRT and found that both CLEAN and LSSA give consistent results in the presence of realistic random flagging scenarios for this observed data set. This comparative analysis demonstrates the effectiveness and robustness of these two algorithms in estimating the H I 21 cm power spectrum from data sets affected by different RFI scenarios.

Keywords: reionization
Dark Matter Deficient Galaxies and Their Member Star Clusters Form Simultaneously during High-velocity Galaxy Collisions in 1.25 pc Resolution Simulations

How diffuse dwarf galaxies that are deficient in dark matter-such as NGC1052-DF2 and NGC1052-DF4-formed remains a mystery. Along with their luminous member globular clusters (GCs), the so-called dark matter deficient galaxies (DMDGs) have challenged observers and theorists alike. Here we report a suite of galaxy collision simulations using the adaptive mesh refinement code ENZO with 1.25 pc resolution, which demonstrates that high-velocity galaxy collisions induce the formation of DMDGs and their star clusters (SCs) simultaneously. With a numerical resolution that is significantly better than our previous study, we resolve the dynamical structure of the produced DMDGs and the detailed formation history of their SCs, which are possible progenitors of the DMDG's member GCs. In particular, we show that a galaxy collision with a high relative velocity of ~300 km s-1, invoking severe shock compression, spawns multiple massive SCs $\left({M}_{\star }\gtrsim {10}^{6}\,{M}_{\odot }\right)$ in <150 Myr after the collision. At the end of the ~800 Myr evolution in our fiducial run, the resulting DMDG of M⋆ ≃ 3.5 × 108 M⊙ hosts 10 luminous MV ≲ -8.5 mag, gravitationally bound SCs with a line-of-sight velocity dispersion 11.2 km s-1. Our study suggests that DMDGs and their luminous member SCs could form simultaneously in high-velocity galaxy collisions while being in line with the key observed properties of NGC1052-DF2 and NGC1052-DF4.

Keywords: galaxy formation; cosmology; galaxy evolution; globular star clusters; star clusters; star formation; hydrodynamical simulations
Energetic Ion Dynamics Near the Cusp Region of Mercury

Energetic ions in Mercury's magnetosphere are very dynamic, similar to those in the magnetosphere of Earth. In this study, we present two energetic proton observations by MErcury Surface, Space ENvironment, GEochemistry and Ranging near the cusp region of Mercury. For one case, we have observed a large flux of energetic protons while the other case has almost no flux, indicating that the near-cusp region may trap energetic particles under particular conditions. In order to understand under what conditions the near-cusp region of Mercury could trap energetic particles, we have used test particle simulations to trace the trajectories of single particles of different energies and pitch angles with a magnetic field model, KT17, that could closely represent the observed in situ magnetic field. Under different magnetic field geometries, the motions of single particles with various energies and pitch angles are different. The test particles can be trapped around the cusp region when the solar disturbance activity that generates the magnetic field local minimum near the cusp region is strong, while the particles cannot be trapped and escape along the magnetic field through the dawnside cusp when there is little solar activity.

Keywords: plasma physics; mercury (planet); planetary magnetospheres; space plasmas
New Pulsating Stars Detected in EA-type Eclipsing-binary Systems Based on TESS Data

Pulsating stars in eclipsing binaries are very important for understanding the structure of stellar interiors through asteroseismology because their absolute parameters such as their masses and radii can be determined with high precision based on photometric and spectroscopic data. The high-precision and continuous time-series photometric data of the Transiting Exoplanet Survey Satellite (TESS) provides an unprecedented opportunity to search for and study these kinds of variable stars in the whole sky. About 1626 Algol-type (EA-type) eclipsing-binary systems were observed by TESS in the 1-45 sectors with 2 minutes short cadence. By analyzing these TESS data, we found 57 new pulsating stars in EA-type binary stars. The preliminary results show that these binary systems have orbital periods in the range from 0.4 to 27 days, while the periods of pulsating components are in the range from 0.02 to 5 days. It is detected that 43 targets follow the correlation between the pulsation and orbital periods of Algol-type oscillating eclipsing binaries (oEA stars), which may indicate that they are typical oEA stars. The other 14 targets may be other types of variable stars in eclipsing-binary systems. These objects are a very interesting source to investigate binary structures and evolution as well as to understand the influences of tidal forces and mass transfer on stellar pulsations.

Keywords: eclipsing binary stars; pulsating variable stars
Water in the Star-forming Region NGC 7129 FIRS 2

Observations of intermediate mass (IM) star formation are expected to highlight the transition between the formation processes of its low and high-mass (HM) counterparts. ${{\rm{H}}}_{2}^{18}{\rm{O}}$ and ${{\rm{H}}}_{2}^{16}{\rm{O}}$ observations of the IM star formation region NGC 7129 FIRS 2 were obtained with the Heterodyne Instrument for the Far-Infrared aboard the Herschel Space Observatory; most as part of the WISH key-program. The radiative transfer program RATRAN was used to model water emission from the envelope of this star-forming region. We consider the envelope in two regions, inner and outer envelope, which are separated by the water freeze-out radius. An outer envelope ortho-H ${}_{2}^{18}$ O/H2 abundance was determined to be 3.5 ± 0.3 × 10-11, and an outer turbulent velocity was determined to be 2.25 ± 0.25 km s-1. The outer envelope ortho-H216O/H2 and para-H216O/H2 abundances were determined to be 1.5 ± 0.5 × 10-8 and 4.5 ± 0.5 × 10-9, respectively. The inner envelope abundances and turbulent velocity could not be constrained due to increased optical depth. The derived values are consistent with those found by low-mass (LM) and HM young stellar object studies of water. While the line shapes and intensities of these lines are more similar to the spectral lines found for LM objects, the turbulent velocity is closer to that seen in HM objects. Lastly, we present a simple visualization tool that we created to show that these abundance results, particularly the limited extent probed by these lines, should not have been a surprise. This tool can be very useful in planning future molecular line observations.

Keywords: interstellar abundances; interstellar molecules; astrochemistry; star formation
Asteroseismic Modeling of 1153 Kepler Red Giant Branch Stars: Improved Stellar Parameters with Gravity-mode Period Spacings and Luminosity Constraints

This paper reports the estimated stellar parameters of 1153 Kepler red giant branch stars determined with asteroseismic modeling. We use radial-mode oscillation frequencies, gravity-mode period spacings, Gaia luminosities, and spectroscopic data to characterize these stars. Compared with previous studies, we find that the two additional observed constraints, i.e., the gravity-mode period spacing and luminosity, significantly improve the precision of fundamental stellar parameters. The typical uncertainties are 2.9% for the mass, 11% for the age, 1.0% for the radius, 0.0039 dex for the surface gravity, and 0.5% for the helium core mass, making this the best-characterized large sample of red giant stars available to date. With better characterizations for these red giants, we recalibrate the seismic scaling relations and study the surface term on the red giant branch. We confirm that the surface term depends on the surface gravity and effective temperature, but there is no significant correlation with metallicity.

Keywords: asteroseismology
Isotope Systematics of Presolar Silicate Grains: New Insights from Magnesium and Silicon

We report on Mg and Si isotope data of 86 presolar silicate grains identified through NanoSIMS oxygen ion imaging in thin sections of carbonaceous and ordinary chondrites. The O, Mg, and Si isotope data of 106 presolar silicates (including grains studied previously by our group) suggest division of O isotope Group 1 grains into four subpopulations: (i) "normal," (ii) 25Mg-rich, (iii) 26Mg-rich, and (iv) 25Mg-poor. Normal Group 1 grains (∼60% of Group 1 grains) formed in the winds of low-mass asymptotic giant branch (AGB) stars, with Mg and Si defining linear arrays with slopes of ∼0.9 and 1.37, respectively, in three-isotope representations, most likely representing Galactic chemical evolution (GCE). The 25Mg-rich grains (∼25%) show enrichments in 25Mg of up to a factor 2.4 relative to solar composition and most likely formed in supernova (SN) ejecta or the winds of intermediate-mass AGB stars. The 26Mg-rich and 25Mg-poor Group 1 grains lie below the Mg GCE line and their isotopic compositions favor origins from supergiants or SNe. The O isotope Group 2 grains show a wide range of Mg-isotopic compositions, similar to Group 1 grains, with likely origins from massive AGB stars, super-AGB stars, supergiants, and SNe. The Mg- and Si-isotopic compositions of Group 4 grains are compatible with previously proposed SN origins. Our results suggest that >30% of presolar silicates formed in the winds of supergiants and in SN ejecta, and that low-mass AGB stars appear to have contributed only some 50% to presolar silicates, less than previously thought.

Keywords: meteorites; circumstellar matter; stellar nucleosynthesis; interstellar dust
The Wave Growth, Saturation, and Electron Heating of Lower Hybrid Waves in the Magnetic Reconnection Exhaust

Lower hybrid waves are commonly observed in magnetic reconnection. Based on in situ measurements and the application of an extended quasi-linear model, we investigate the occurrence, saturation, and electron heating of lower hybrid waves in the region of magnetopause reconnection outflows. Lower hybrid waves are statistically favored when the density gradient length scale (L n ) normalized by the ion gyroradius (ρ i ) is small. The occurrence of lower hybrid waves is significantly higher in the regime of L n /ρ i < 1 and plasma beta β < 1. These features of wave occurrence are consistent with the linear theory of the wave growth rate. Evidence indicates that the saturation level and the parallel electron heating of waves both increase as the normalized gradient scale L n /ρ i decreases. The parallel electron temperature increases ~30%-70% as L n /ρ i < 1. We show that the observation of saturation and electron heating is consistent with an extended quasi-linear model. In this scenario, lower hybrid waves are driven by density gradients and then quickly saturate in tens of ion gyroperiods. The parallel electron heating from lower hybrid waves is achieved through Landau damping before the nonlinear saturation. Our results provide comprehensive evidence for an end-to-end process of electron heating through lower hybrid waves in reconnection exhausts. L n /ρ i is the key parameter that determines the extent of the wave growth, saturation energy, and electron heating in this wave-particle interaction process.

Keywords: space plasmas; planetary magnetospheres
ASASSN-14ms: The Most Energetic Known Explosion of a Type Ibn Supernova and Its Physical Origin

ASASSN-14ms may represent the most luminous Type Ibn supernova (SN Ibn) ever detected, with an absolute U-band magnitude brighter than -22.0 mag and a total bolometric luminosity >1.0 × 1044 erg s-1 near maximum light. The early-time spectra of this SN are characterized by a blue continuum on which are superimposed narrow P Cygni profile lines of He I, suggesting the presence of slowly moving (~1000 km s-1), He-rich circumstellar material (CSM). At 1-2 months after maximum brightness, the He I line profiles become only slightly broader, with blueshifted velocities of 2000-3000 km s-1, consistent with the CSM shell being continuously accelerated by the SN light and ejecta. Like most SNe Ibn, the light curves of ASASSN-14ms show rapid post-peak evolution, dropping by ~7 mag in the V band over three months. Such a rapid post-peak decline and high luminosity can be explained by interaction between SN ejecta and helium-rich CSM of 0.9 M⊙ at a distance of ~1015 cm. The CSM around ASASSN-14ms is estimated to originate from a pre-explosion event with a mass-loss rate of 6.7 M⊙ yr-1 (assuming a velocity of ~1000 km s-1), which is consistent with abundant He-rich material violently ejected during the late Wolf-Rayet (WN9-11 or Opfe) stage. After examining the light curves for a sample of SNe Ibn, we find that the more luminous ones tend to have slower post-peak decline rates, reflecting that the observed differences may arise primarily from discrepancies in the CSM distribution around the massive progenitors.

Keywords: circumstellar dust; stellar mass loss
Line Profiles of Forbidden Emission Lines and What They Can Tell Us About Protoplanetary Disk Winds

Emission in forbidden lines of oxygen, neon, and other species are commonly used to trace winds from protoplanetary disks. Using Cloudy, we calculate such emission for parametrized wind models of the magnetothermal type, following Bai et al. These models share characteristics with both photoevaporative and magnetocentrifugal winds, which can be regarded as end members, and are favored by recent theoretical research. Both broad and narrow low-velocity components of the lines can be produced with plausible wind parameters, something that traditional wind models have difficulty with. Line luminosities, blueshifts, and widths, as well as trends of these with accretion luminosity and disk inclination, are in general accordance with observations.

Keywords: protoplanetary disks; atomic spectroscopy