adsabs/SciX_UAT_keywords huggingface dataset:
Stellar X-Ray Activity and Habitability Revealed by the ROSAT Sky Survey

Using the homogeneous X-ray catalog from ROSAT observations, we conducted a comprehensive investigation into stellar X-ray activity–rotation relations for both single and binary stars. Generally, the relation for single stars consists of two distinct regions: a weak decay region, indicating a continued dependence of the magnetic dynamo on stellar rotation rather than a saturation regime with constant activity, and a rapid decay region, where X-ray activity is strongly correlated with the Rossby number. Detailed analysis reveals more fine structures within the relation: in the extremely fast-rotating regime, a decrease in X-ray activity was observed with increasing rotation rate, referred to as supersaturation, while in the extremely slow-rotating region, the relation flattens, mainly due to the scattering of F stars. This scattering may result from intrinsic variability in stellar activities over one stellar cycle or the presence of different dynamo mechanisms. Binaries exhibit a similar relation to that of single stars while the limited sample size prevented the identification of fine structures in the relation for binaries. We calculated the mass-loss rates of planetary atmospheres triggered by X-ray emissions from host stars. Our findings indicate that for an Earthlike planet within the stellar habitable zone, it would easily lose its entire primordial H/He envelope (equating to about 1% of the planetary mass).

Keywords: habitable zone; late-type stars; stellar activity; stellar rotation; x-ray stars
Re-examining the Radial Distributions of M13 Multiple Populations

We seek to resolve the tension in the literature regarding the presence of radially segregated multiple populations in the Galactic globular cluster M13. Previous studies of this nearby cluster have presented discordant results about the degree of dynamical mixing in M13's inner region. Using ground-based (UBVI) photometry, we show that cumulative radial distributions of stars on the blue and red sides of the red giant branch are statistically identical. Interestingly, these results are obtained using data from large-aperture, ground-based telescopes as well as a more modestly sized instrument, and both are in agreement with previous work done using Hubble Space Telescope and Strömgren photometry. Results are derived using the CU,B,I index, shown to be sensitive to compositional differences. We discuss our conclusions that the chemically distinct populations within M13 may be dynamically mixed in the context of published results from simulations.

Keywords: globular star clusters; red giant branch; hertzsprung russell diagram; broad band photometry; dynamical evolution
Unexpected Dancing Partners: Tracing the Coherence between the Spin and Motion of Dark Matter Halos

A recent study conducted using CALIFA survey data has found that the orbital motions of neighbor galaxies are coherent with the spin direction of a target galaxy on scales of many megaparsecs. We study this so-called "large-scale coherence" phenomenon using N-body cosmological simulations. We confirm a strong coherence signal within 1 Mpc h -1 of a target galaxy, reaching out to 6 Mpc h -1. We divide the simulation halos into subsamples based on mass, spin, merger history, and local halo number density for both target and neighbor halos. We find a clear dependency on the mass of the target halo only. Another key parameter is the local number density of both target and neighbor halos, with high-density regions such as clusters and groups providing the strongest coherence signals, rather than filaments or lower-density regions. However we do not find a clear dependency on halo spin or time since last major merger. The most striking result we find is that the signal can be detected up to 15 Mpc h -1 from massive halos. These results provide valuable lessons on how observational studies could more clearly detect coherence, and we discuss the implications of our results for the origins of large-scale coherence.

Keywords: large-scale structure of the universe; galaxy dynamics; galaxy evolution; galaxy kinematics; n-body simulations
Forward Modeling Populations of Flares from Tidal Disruptions of Stars by Supermassive Black Holes

Detections of the tidal disruption flares (TDFs) of stars by supermassive black holes (SMBHs) are rapidly accumulating as optical surveys improve. These detections may provide constraints on SMBH demographics, stellar dynamics, and stellar evolution in galaxies. To maximize this scientific impact, we require a better understanding of how astrophysical parameters interact with survey selection effects in setting the properties of detected flares. We develop a framework for modeling the distributions of optical TDF detections in surveys across attributes of the host galaxies and the flares themselves. This model folds in effects of the stellar disruption rate in each galaxy, the flare luminosity and temperature distributions, the effects of obscuration and reddening by dust in the host galaxy, and survey selection criteria. We directly apply this model to the sample of TDFs detected by the Zwicky Transient Facility, and find that the overall flare detection rate is in line with simple theoretical expectation. The model can also reproduce the distribution of total stellar mass and redshift of the host galaxies, but fails to match all details of the detected flares, such as their luminosity and temperature distributions. We also find that dust obscuration likely plays an important role in suppressing the TDF detection rate in star-forming galaxies. While we do not find that the unusual preference of TDFs to have hosts in post-starburst galaxies in the "green valley" can be entirely explained by selection effects, our model can help to quantify the true rate enhancement in those galaxies.

Keywords: black holes; black hole physics; accretion; tidal disruption; surveys; sky surveys; extragalactic astronomy; wide-field telescopes; astronomy data modeling; galaxy dynamics; galaxy evolution
Wide-spectral-band Nuller Insensitive to Finite Stellar Angular Diameter with a One-dimensional Diffraction-limited Coronagraph

Potentially habitable planets around nearby stars less massive than solar-type stars could join targets of the spectroscopy of the planetary reflected light with future space telescopes. However, the orbits of most of these planets occur near the diffraction limit for 6 m diameter telescopes. Thus, while securing contrast-mitigation ability under a broad spectral bandwidth and a finite stellar angular diameter, we must maintain planetary throughput even at the diffraction-limited angles to be able to reduce the effect of the photon noise within a reasonable observation time. A one-dimensional diffraction-limited coronagraph (1DDLC) observes planets near the diffraction limit with undistorted point spread functions but has a finite-stellar diameter problem in wideband use. This study presents a method for wide-spectral-band nulling insensitive to stellar-angular-diameter by adding a fiber nulling with a Lyot-plane phase mask to the 1DDLC. Designing the pattern of the Lyot-plane mask function focuses on the parity of the amplitude spread function of light. Our numerical simulation shows that the planetary throughput (including the fiber-coupling efficiency) can reach about 11% for about 1.35-λ/D planetary separation almost independently of the spectral bandwidth. The simulation also shows the raw contrast of about 4 × 10‑8 (the spectral bandwidth of 25%) and 5 × 10‑10 (the spectral bandwidth of 10%) for 3 × 10‑2 λ/D stellar angular diameter. The planetary throughput depends on the planetary azimuthal angle, which may degrade the exploration efficiency compared to an isotropic throughput but is partially offset the wide spectral band.

Keywords: astrobiology; astronomical optics; direct imaging; high contrast techniques; coronagraphic imaging
Extreme Solar Flare-driven Short-wave Fadeout Observed by SuperDARN ZHO Radar

Based on the observations from the Super Dual Auroral Radar Network at the Zhongshan Station (-74.9 MLAT, 97.2 MLON) and GOES satellites X-ray sensor, we present the first statistical study of the dayside ionospheric short-wave fadeout (SWF) events on the Southern Hemispheric high latitude from the years 2010-2019 and provide a normal characteristic of SWF with onset of 6 minutes 54 s, blackout of 20 minutes 24 s, and recovery of 39 minutes 36 s, respectively. All the SWF events in this work are selected to be caused by extreme flares. The statistical analysis shows both short-type and long-type SWF onset phases. Onset/blackout phase duration of long events is highly correlated with flare duration (0.79, 0.60), the SWF is mainly driven by the flare radiation profile, and the soft X-ray flux rise rate is higher for short-onset events than for most long-onset events, which is the main reason for the difference between the two types of events. In addition, the effect of ionospheric sluggishness on long-onset events also needs to be considered. The relationship between each phase's durations of long SWFs and the effective peak X-ray flux is not obvious. However, the correlation between the integrated effective X-ray flux and the onset/blackout phase duration of long events is significant.

Keywords: solar x-ray flares; photoionization; earth ionosphere
Three-day Forecasting of Solar Wind Speed Using SDO/AIA Extreme-ultraviolet Images by a Deep-learning Model

In this study, we forecast solar wind speed for the next 3 days with a 6 hr cadence using a deep-learning model. For this we use Solar Dynamics Observatory/Atmospheric Imaging Assembly 211 and 193 Å images together with solar wind speeds for the last 5 days as input data. The total period of the data is from 2010 May to 2020 December. We divide them into a training set (January-August), validation set (September), and test set (October-December), to consider the solar cycle effect. The deep-learning model consists of two networks: a convolutional layer-based network for images and a dense layer-based network for solar wind speeds. Our main results are as follows. First, our model successfully predicts the solar wind speed for the next 3 days. The rms error (RMSE) of our model is from 37.4 km s-1 (for the 6 hr prediction) to 68.2 km s-1 (for the 72 hr prediction), and the correlation coefficient is from 0.92 to 0.67. These results are much better than those of previous studies. Second, the model can predict sudden increase of solar wind speeds caused by large equatorial coronal holes. Third, solar wind speeds predicted by our model are more consistent with observations than those by the Wang-Sheely-Arge-ENLIL model, especially in high-speed-stream regions. It is also noted that our model cannot predict solar wind speed enhancement by coronal mass ejections. Our study demonstrates the effectiveness of deep learning for solar wind speed prediction, with potential applications in space weather forecasting.

Keywords: the sun; convolutional neural networks; solar wind
Orbital Migration of Interacting Stellar Mass Black Holes in Disks around Supermassive Black Holes. II. Spins and Incoming Objects

The masses, rates, and spins of merging stellar mass binary black holes (BBHs) detected by aLIGO and Virgo provide challenges to traditional BBH formation and merger scenarios. An active galactic nucleus (AGN) disk provides a promising additional merger channel because of the powerful influence of the gas that drives orbital evolution, makes encounters dissipative, and leads to migration. Previous work showed that stellar mass black holes (sBHs) in an AGN disk migrate to regions of the disk, known as migration traps, where positive and negative gas torques cancel out, leading to frequent BBH formation. Here we build on that work by simulating the evolution of additional sBHs that enter the inner disk by either migration or inclination reduction. We also examine whether the BBHs formed in our models have retrograde or prograde orbits around their centers of mass with respect to the disk, determining the orientation of the spin of the merged BBHs relative to the disk. Orbiters entering the inner disk form BBHs with sBHs on resonant orbits near the migration trap. When these sBHs reach ≳80 M⊙, they form BBHs with sBHs in the migration trap, which reach ∼1000 M⊙ over 10 Myr. We find 68% of the BBHs in our simulation orbit in the retrograde direction, which implies that BBHs in our merger channel will have small dimensionless aligned spins, χeff. Overall, our models produce BBHs that resemble both the majority of BBH mergers detected thus far (0.66-120 Gpc-3 yr-1) and two recent unusual detections, GW190412 (∼0.3 Gpc-3 yr-1) and GW190521 (∼0.1 Gpc-3 yr-1).

Keywords: black hole physics; active galactic nuclei; ligo; intermediate-mass black holes; supermassive black holes
Faint Comet Detection with Unistellar eVscopes

We present eVscope observations of comets 12P/Pons-Brooks and C/2023 A3 (Tsuchinshan-ATLAS) when their magnitudes were greater than 16th magnitude. From a set of two observations of 12P taken on 2023 June 19 and 20, we measure an apparent magnitude of G = 16.59 ± 0.31. From four sets of observations of C/2023 A3 taken on 2023 April 14, 25, 26, and May 9, we measure apparent magnitudes of G = 16.78 ± 0.41, 16.55 ± 0.29, 16.71 ± 0.28, 16.59 ± 0.18 respectively. These images were taken from Unistellar telescope models: eVscope 1 and 2. We find an average background value of G = 17.35 ± 0.21.

Keywords: telescopes; automated telescopes; ground telescopes; comets
A General Formulation for Computing Spherical Helioseismic Sensitivity Kernels while Incorporating Systematical Effects

As helioseismology matures and turns into a precision science, modeling finite-frequency, geometric, and systematical effects is becoming increasingly important. Here we introduce a general formulation for treating perturbations of arbitrary tensor rank in spherical geometry using fundamental ideas of quantum mechanics and their extensions in geophysics. We include line-of-sight projections and center-to-limb differences in line formation heights in our analysis. We demonstrate the technique by computing a travel-time sensitivity kernel for sound-speed perturbations. The analysis produces the spherical harmonic coefficients of the sensitivity kernels, which leads to better-posed and computationally efficient inverse problems.

Keywords: helioseismology; helioseismic pulsations; analytical mathematics; perturbation methods; computational astronomy
JWST Reveals CO Ice, Concentrated CO2 Deposits, and Evidence for Carbonates Potentially Sourced from Ariel's Interior

The Uranian moon Ariel exhibits a diversity of geologically young landforms, with a surface composition rich in CO2 ice. The origin of CO2 and other species, however, remains uncertain. We report observations of Ariel's leading and trailing hemispheres, collected with NIRSpec (2.87–5.10 μm) on the James Webb Space Telescope. These data shed new light on Ariel's spectral properties, revealing a double-lobed CO2 ice scattering peak centered near 4.20 and 4.25 μm, with the 4.25 μm lobe possibly representing the largest CO2 Fresnel peak yet observed in the solar system. A prominent 4.38 μm 13CO2 ice feature is also present, as is a 4.90 μm band that results from 12CO2 ice. The spectra reveal a 4.67 μm 12CO ice band and a broad 4.02 μm band that might result from carbonate minerals. The data confirm that features associated with CO2 and CO are notably stronger on Ariel's trailing hemisphere compared to its leading hemisphere. We compared the detected CO2 features to synthetic spectra of CO2 ice and mixtures of CO2 with CO, H2O, and amorphous carbon, finding that CO2 could be concentrated in deposits thicker than ∼10 mm on Ariel's trailing hemisphere. Comparison to laboratory data indicates that CO is likely mixed with CO2. The evidence for thick CO2 ice deposits and the possible presence of carbonates on both hemispheres suggests that some carbon oxides could be sourced from Ariel's interior, with their surface distributions modified by charged particle bombardment, sublimation, and seasonal migration of CO and CO2 from high to low latitudes.

Keywords: carbon dioxide; ice spectroscopy; surface ices; surface processes; surface composition; james webb space telescope; uranian satellites
Dark Matter Halo Masses from Abundance Matching and Kinematics: Tensions for the Milky Way and M31

The dark matter halo masses of galaxies can be estimated from their stellar masses via abundance matching (AM). For both the Milky Way and M31, the AM mass is higher than the mass inferred from kinematics. The higher AM masses exacerbate the missing satellite problem. The difference is especially pronounced for M31, for which ${M}_{200}^{\mathrm{AM}}\gtrsim {10}^{13}\,{M}_{\odot }$ but ${M}_{200}^{\mathrm{kin}}\lt 2\times {10}^{12}\,{M}_{\odot }$ . This is more than expected from scatter in the AM relation, and may suggest the need for separate AM relations for early and late type galaxies.

Keywords: galaxy dark matter halos; milky way dark matter halo
CAMEMBERT: A Mini-Neptunes General Circulation Model Intercomparison, Protocol Version 1.0.A CUISINES Model Intercomparison Project

With an increased focus on the observing and modeling of mini-Neptunes, there comes a need to better understand the tools we use to model their atmospheres. In this Paper, we present the protocol for the Comparing Atmospheric Models of Extrasolar Mini-Neptunes Building and Envisioning Retrievals and Transits, CAMEMBERT, project, an intercomparison of general circulation models (GCMs) used by the exoplanetary science community to simulate the atmospheres of mini-Neptunes. We focus on two targets well studied both observationally and theoretically with planned JWST cycle 1 observations: the warm GJ 1214b and the cooler K2-18b. For each target, we consider a temperature-forced case, a clear sky dual-gray radiative transfer case, and a clear sky multiband radiative transfer case, covering a range of complexities and configurations where we know differences exist between GCMs in the literature. This Paper presents all the details necessary to participate in the intercomparison, with the intention of presenting the results in future papers. Currently, there are eight GCMs participating (EXOCAM, EXO-FMS, FMS PCM, GENERIC PCM, MITGCM, RM-GCM, THOR, and the Unified Model), and membership in the project remains open. Those interested in participating are invited to contact the authors.

Keywords: mini neptunes; exoplanet atmospheres
Continuous Gravitational Waves from Galactic Neutron Stars: Demography, Detectability, and Prospects

We study the prospects for the detection of continuous gravitational signals from normal Galactic neutron stars, i.e., nonrecycled stars. We use a synthetic population generated by evolving stellar remnants in time, according to several models. We consider the most recent constraints set by all-sky searches for continuous gravitational waves and use them for our detectability criteria. We discuss the detection prospects for the current and the next generation of gravitational-wave detectors. We find that neutron stars whose ellipticity is solely caused by magnetic deformations cannot produce any detectable signal, not even by third-generation detectors. The currently detectable sources all have B ≲ 1012 G and deformations that are not solely due to the magnetic field. For these, we find in fact that the larger the magnetic field, the higher the ellipticity required for the signal to be detectable, and this ellipticity is well above the value induced by the magnetic field. Third-generation detectors such as the Einstein Telescope and Cosmic Explorer will be able to detect up to ≈250 more sources than current detectors. We briefly treat the case of recycled neutron stars with a simplified model. We find that continuous gravitational waves from these objects will likely remain elusive to detection by current detectors, but should be detectable with the next generation of detectors.

Keywords: gravitational wave astronomy; gravitational wave sources; gravitational wave detectors; neutron stars; pulsars; stellar populations
A 4-8 GHz Galactic Center Search for Periodic Technosignatures

Radio searches for extraterrestrial intelligence have mainly targeted the discovery of narrowband continuous-wave beacons and artificially dispersed broadband bursts. Periodic pulse trains, in comparison to the above technosignature morphologies, offer an energetically efficient means of interstellar transmission. A rotating beacon at the Galactic Center (GC), in particular, would be highly advantageous for galaxy-wide communications. Here, we present blipss, a CPU-based open-source software that uses a fast folding algorithm (FFA) to uncover channel-wide periodic signals in radio dynamic spectra. Running blipss on 4.5 hr of 4-8 GHz data gathered with the Robert C. Byrd Green Bank Telescope, we searched the central $6^{\prime} $ of our galaxy for kHz-wide signals with periods between 11 and 100 s and duty cycles (δ) between 10% and 50%. Our searches, to our knowledge, constitute the first FFA exploration for periodic alien technosignatures. We report a nondetection of channel-wide periodic signals in our data. Thus, we constrain the abundance of 4-8 GHz extraterrestrial transmitters of kHz-wide periodic pulsed signals to fewer than one in about 600,000 stars at the GC above a 7σ equivalent isotropic radiated power of ≈2 × 1018 W at δ ≃ 10%. From an astrophysics standpoint, blipss, with its utilization of a per-channel FFA, can enable the discovery of signals with exotic radio frequency sweeps departing from the standard cold plasma dispersion law.

Keywords: galactic center; period search; search for extraterrestrial intelligence; technosignatures
Exploring the Jet Formation in Binary Systems Applying 3D MHD Simulations

We investigate the formation of an ideal magnetized jet that originates from a disk acting as a boundary by conducting axisymmetric MHD simulations. Our simulations demonstrate that the magnetized jet is consistently launched and reaches a stable state. To further advance our study, we extended the model setup to three dimensions and performed 3D MHD simulations of the jet launched from a disk surface, achieving a stable and appropriate model setup. Additionally, we expanded our study by incorporating the companion star and examining the influence of the Roche potential on the jet material. Specifically, we investigate whether including the companion star in the model significantly affects the dynamical evolution of the jet. Our findings reveal the formation of an arc-like structure in the density map of the jet cross section, which is attributed to the direct tidal effects. This implies that while the primary physical effects and characteristics of the outflow on a larger scale are attributed to the host accretion disk, the direct tidal effects on the jet dynamics have a substantial impact, particularly in the vicinity of the Roche lobe and toward the secondary star.

Keywords: stellar jets; binary stars; magnetohydrodynamics; magnetohydrodynamical simulations