adsabs/SciX_UAT_keywords huggingface dataset:
Supporting Evidence for a Galactic Lyα Background from Cassini UVIS Data

Cassini UVIS interplanetary hydrogen Lyα measurements from 2003 to 2004, obtained from a heliospheric downwind to sidewind location on approach to Saturn and during the first Saturn orbit, are presented and fit by a heliospheric hot density model with solar illumination. Adding the recently proposed 43 ± 3 Rayleigh (R) isotropic galactic hydrogen Lyα signal derived from New Horizons data improves our model's ability to fit the observed Cassini "27 day" signal modulations from both upwind and downwind directions. Our modeling of the UVIS data favors a galactic Lyα background of ~40-100R over a model with no significant galactic background.

Keywords: interstellar medium wind
Breaching the Limit: Formation of GW190521-like and IMBH Mergers in Young Massive Clusters

The LIGO-Virgo-Kagra Collaboration (LVC) discovered recently GW190521, a gravitational wave (GW) source associated with the merger between two black holes (BHs) with mass 66 and >85 M⊙. GW190521 represents the first BH binary merger with a primary mass falling in the upper-mass gap and the first leaving behind an ~150 M⊙ remnant. So far, the LVC has reported the discovery of four further mergers having a total mass >100 M⊙, i.e., in the intermediate-mass black hole (IMBH) mass range. Here, we discuss results from a series of 80 N-body simulations of young massive clusters that implement relativistic corrections to follow compact object mergers. We discover the development of a GW190521-like system as the result of a third-generation merger, and four IMBH-BH mergers with total mass (300-350)M⊙. We show that these IMBH-BH mergers are low-frequency GW sources detectable with LISA and Deci-hertz Interferometer Gravitational wave Observatory (DECIGO) out to redshift z = 0.01-0.1 and z > 100, and we discuss how their detection could help unraveling IMBH natal spins. For the GW190521 test case, we show that the third-generation merger remnant has a spin and effective spin parameter that matches the 90% credible interval measured for GW190521 better than a simpler double merger and comparable to a single merger. Due to GW recoil kicks, we show that retaining the products of these mergers require birth sites with escape velocities ≳50-100 km s-1, values typically attained in galactic nuclei and massive clusters with steep density profiles.

Keywords: astrophysical black holes; black holes; intermediate-mass black holes; stellar mass black holes; young star clusters; globular star clusters; galaxy nuclei; gravitational wave astronomy; gravitational wave detectors; gravitational wave sources
Perfecting Our Set of Spectrophotometric Standard DA White Dwarfs

We verified for photometric stability a set of DA white dwarfs with Hubble Space Telescope magnitudes from the near-ultraviolet to the near-infrared and ground-based spectroscopy by using time-spaced observations from the Las Cumbres Observatory network of telescopes. The initial list of 38 stars was whittled to 32 final ones, which comprise a high-quality set of spectrophotometric standards. These stars are homogeneously distributed around the sky and are all fainter than r ~ 16.5 mag. Their distribution is such that at least two of them would be available to be observed from any observatory on the ground at any time at airmass less than 2. Light curves and different variability indices from the Las Cumbres Observatory data were used to determine the stability of the candidate standards. When available, Pan-STARRS1, Zwicky Transient Facility, and TESS data were also used to confirm the star classification. Our analysis showed that four DA white dwarfs may exhibit evidence of photometric variability, while a fifth is cooler than our established lower temperature limit, and a sixth star might be a binary. In some instances, due to the presence of faint nearby red sources, care should be used when observing a few of the spectrophotometric standards with ground-based telescopes. Light curves and finding charts for all the stars are provided.

Keywords: flux calibration; photometric standard stars; spectrophotometric standards; variable stars; da stars; white dwarf stars; time series analysis
Properties of Flare-imminent versus Flare-quiet Active Regions from the Chromosphere through the Corona. I. Introduction of the AIA Active Region Patches (AARPs)

We begin here a series of papers examining the chromospheric and coronal properties of solar active regions. This first paper describes an extensive data set of images from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory curated for large-sample analysis of this topic. Based on (and constructed to coordinate with) the "Active Region Patches" as identified by the pipeline data analysis system for the Helioseismic and Magnetic Imager on the same mission (the "HARPs"), the "AIA Active Region Patches" (AARPs), described herein, comprise an unbiased multiwavelength set of FITS files downsampled spatially only by way of HARP-centered patch extractions (full spatial sampling is retained), and downsampled in the temporal domain but still able to describe both short-lived kinematics and longer-term trends. The AARPs database enables physics-informed parameterization and analysis using nonparametric discriminant analysis in Paper II of this series, and is validated for analysis using differential emission measure techniques. The AARP data set presently covers mid-2010 through 2018 December, is ≈9 TB in size, and is available through the Solar Data Analysis Center.

Keywords: solar atmosphere; solar corona; solar active regions
Unveiling the Temporal Properties of MAXI J1820+070 through AstroSat Observations

We present here the results of the first broadband simultaneous spectral and temporal studies of the newly detected black hole binary MAXI J1820+070 as seen by Soft X-ray Telescope and Large Area X-ray Proportional Counter (LAXPC) on board AstroSat. The observed combined spectra in the energy range 0.7-80 keV were well modeled using disk blackbody emission, thermal Comptonization, and a reflection component. The spectral analysis revealed that the source was in its hard spectral state (Γ = 1.61) with a cool disk (kTin = 0.22 keV). We report the energy dependent time-lag and root mean squared (rms) variability at different frequencies in the energy range 3-80 keV using LAXPC data. We also modeled the flux variability using a single-zone stochastic propagation model to quantify the observed energy dependence of time lag and fractional rms variability, and then compared the results with that of Cygnus X-1. Additionally, we confirm the detection of a quasi-periodic oscillation with the centroid frequency at 47.7 mHz.

Keywords: black hole physics; stellar accretion disks; low-mass x-ray binary stars; x-ray transient sources; stellar accretion; x-ray astronomy; stellar mass black holes; black holes
Lyα Halos around [O III]-selected Galaxies in HETDEX

We present extended Lyα emission out to 800 kpc of 1034 [O III]-selected galaxies at redshifts 1.9 < z < 2.35 using the Hobby-Eberly Telescope Dark Energy Experiment. The locations and redshifts of the galaxies are taken from the 3D-HST survey. The median-stacked surface brightness profile of the Lyα emission of the [O III]-selected galaxies agrees well with that of 968 bright Lyα-emitting galaxies (LAEs) at r > 40 kpc from the galaxy centers. The surface brightness in the inner parts (r < 10 kpc) around the [O III]-selected galaxies, however, is 10 times fainter than that of the LAEs. Our results are consistent with the notion that photons dominating the outer regions of the Lyα halos are not produced in the central galaxies but originate outside of them.

Keywords: high-redshift galaxies; circumgalactic medium; intergalactic medium; galaxy environments
H I HOD. I. The Halo Occupation Distribution of H I Galaxies

The next generation of galaxy surveys will provide more precise measurements of galaxy clustering than have previously been possible. The 21 cm radio signals that are emitted from neutral atomic hydrogen (H I) gas will be detected by large-area radio surveys such as the Widefield Australian Square Kilometre Array (SKA) Pathfinder L-band Legacy All-sky Blind Survey and SKA, and deliver galaxy positions and velocities that can be used to measure galaxy clustering statistics. However, to harness this information to improve our cosmological understanding and learn about the physics of dark matter and dark energy, we need to accurately model the manner in which galaxies detected in H I trace the underlying matter distribution of the universe. For this purpose, we develop a new H I-based halo occupation distribution (HOD) model, which makes predictions for the number of galaxies present in dark matter halos conditional on their H I mass. The parameterized HOD model is fit and validated using the DARK SAGE semi-analytic model, where we show that the HOD parameters can be modeled by simple linear and quadratic functions of the H I mass. However, we also find that the clustering predicted by the HOD depends sensitively on the radial distributions of the H I galaxies within their host dark matter halos, which does not follow the Navarro-Frenk-White profile in the DARK SAGE simulation. As such, this work enables-for the first time-a simple prescription for placing galaxies of different H I masses within dark matter halos in a way that is able to reproduce the H I mass-dependent galaxy clustering and H I mass function simultaneously and without requiring knowledge of the optical properties of the galaxies. Further efforts are required to demonstrate that this model can be used to produce large ensembles of mock galaxy catalogs for upcoming surveys.

Keywords: cosmology; large-scale structure of the universe; galaxy dark matter halos
Energetic Electron Acceleration by Ion-scale Magnetic Islands in Turbulent Magnetic Reconnection: Particle-in-cell Simulations and ARTEMIS Observations

Particle-in-cell simulations show that numerous ion-scale magnetic islands can be formed in a turbulent magnetic reconnection region. These islands can confine and accelerate electrons to high energies effectively, causing the energetic electron energy flux to peak at the center of each island. ARTEMIS spacecraft observations of turbulent reconnection outflows in Earth's magnetotail reveal that peaks in the energetic electron energy flux are well correlated with bipolar signatures of reconnected magnetic field, which are indicative of ion-scale magnetic islands, providing observational evidence for this acceleration process.

Keywords: heliosphere; interplanetary particle acceleration; solar magnetic reconnection
Circumstellar Medium Interaction in SN 2018lab, A Low-luminosity Type IIP Supernova Observed with TESS

We present photometric and spectroscopic data of SN 2018lab, a low-luminosity Type IIP supernova (LLSN) with a V-band peak luminosity of -15.1 ± 0.1 mag. SN 2018lab was discovered by the Distance Less Than 40 Mpc (DLT40) SN survey only 0.73 days post-explosion, as determined by observations from the Transiting Exoplanet Survey Satellite (TESS). TESS observations of SN 2018lab yield a densely sampled, fast-rising, early-time light curve likely powered by ejecta-circumstellar medium (CSM) interaction. The blueshifted, broadened flash feature in the earliest spectra (<2 days) of SN 2018lab provides further evidence for ejecta-CSM interaction. The early emission features in the spectra of SN 2018lab are well described by models of a red supergiant progenitor with an extended envelope and a close-in CSM. As one of the few LLSNe with observed flash features, SN 2018lab highlights the need for more early spectra to explain the diversity of the flash feature morphology of Type II SNe.

Keywords: supernovae; core-collapse supernovae; type ii supernovae; circumstellar matter
A Case Study of the Induced Magnetosphere Boundary at the Martian Subsolar Region

One Martian induced magnetosphere boundary (IMB) crossing at the subsolar region is analyzed here with multiple instruments on board MAVEN. Properties of the magnetic field and particles around the IMB are evaluated. We find different trends of variation in magnetic field components at the two sides of an interface coincident with the previously defined ion composition boundary. This case shows the IMB at the Martian dayside could be divided into three parts: two regions (denoted as R1 and R2), with different field and plasma properties, and an interface between them. Currents found in R1 and R2 are flowing in antiparallel, and the current density in R2 (at lower altitude) is significantly larger than that in R1 (at higher altitude). Results indicate the interaction between Mars and the solar wind could induce strong currents in the IMB, which are with antiparallel current directions and separated by an interface where the ion composition changes. This could be a typical feature that occurred during the interaction between the solar wind and the nonmagnetized planets.

Keywords: mars; planetary boundary layers
CAHA/PPAK Integral-field Spectroscopic Observations of M81. II. Testing Photoionization Models in a Spatially Resolved LINER

The origin of the low-ionization nuclear emission-line region (LINER) prevalent in local galaxies and its relationship with supermassive black holes have been debated for decades. We perform a comprehensive evaluation of traditional photoionization models against the circumnuclear ionized gas in M81, for which recent CAHA/PPAK integral-field spectroscopic observations reveal a LINER characteristic out to a galactocentric radius of ~1 kpc. Constructed with the photoionization code CLOUDY, the models have the novel aspect of their primary parameters being well constrained by extensive observations of a prototypical low-luminosity active galactic nucleus (LLAGN) and an old stellar bulge in M81. Additionally, these models incorporate a reasonably broad range of uncertain nebular properties. It is found that the integrated photoionization by the LLAGN and hot, low-mass stars distributed in the bulge can roughly reproduce the observed radial intensity distributions of the Hα, Hβ, and [N II] lines, with the bulge stars dominating the ionizing flux at radii ≳200 pc. However, the models generally fail to reproduce a similarly declining profile of the [O III] line or an accordingly flat profile of the [O III]/Hβ ratio. This clearly points to a deficiency of ionizing photons in the outer regions despite an extended photoionization source. The discrepancy might be alleviated if much of the observed [O III] line arose from a bulge-filling, low-density gas surrounding a denser, Hα-emitting disk, or by a higher AGN luminosity in the recent past. The case of M81 has important implications for the ionization mechanism of LINERs and low-ionization emission-line regions in general.

Keywords: active galactic nuclei; photoionization; galaxy nuclei; galaxy spectroscopy
High-resolution Spectra for a Wide Range of Habitable Zone Planets around Sun-like Stars

The search for life in the universe is currently focused on Earth-analog planets. However, we should be prepared to find a diversity of terrestrial exoplanets not only in terms of host star but also in terms of surface environment. Simulated high-resolution spectra of habitable planets covering a wide parameter space are essential in training retrieval tools, optimizing observing strategies, and interpreting upcoming observations. Ground-based extremely large telescopes like ELT, GMT, and TMT and future space-based mission concepts like Origins, HabEx, and LUVOIR are designed to have the capability of characterizing a variety of potentially habitable worlds. Some of these telescopes will use high-precision radial velocity techniques to obtain the required high-resolution spectra (R ≈ 100,000) needed to characterize potentially habitable exoplanets. Here we present a database of high-resolution (0.01 cm-1) reflection and emission spectra for simulated exoplanets with a wide range of surfaces, receiving similar irradiation as Earth around 12 different host stars from F0 to K7. Depending on surface type and host star, we show differences in spectral feature strength as well as overall reflectance, emission, and star-to-planet contrast ratio of terrestrial planets in the habitable zone of their host stars. Accounting for the wavelength-dependent interaction of the stellar flux and the surface will help identify the best targets for upcoming spectral observations in the visible and infrared. All of our spectra and model profiles are available online.

Keywords: exoplanet atmospheres; habitable planets; exoplanet surface composition; exoplanet catalogs; exoplanet astronomy
Observations of the 2022 September 5 Solar Energetic Particle Event at 15 Solar Radii

On 2022 September 5, Parker Solar Probe (Parker) observed a large solar energetic particle (SEP) event at the unprecedented distance of only 15 R S from the Sun. The observations from the Integrated Science Investigation of the Sun (IS⊙IS) obtained over the course of this event are remarkably rich, and an overview is presented here. IS⊙IS is capable of measuring ions from 20 keV to over 100 MeV nuc‑1 and electrons from 30 keV to 6 MeV; here, we primarily focus on the proton and helium measurements above 80 keV. Among the surprising results are evidence of inverse velocity dispersion at energies above 1 MeV during the onset of the event, a sharp decrease in the energetic particle intensities at all energies at the interplanetary shock crossing, and repeated short durations of highly anisotropic sunward flow. Many changes in the SEP intensities, anisotropy, and spectral steepness are coincident with solar wind structure boundaries identified using the Parker solar wind magnetic field and plasma data. However, there are significant changes that are not correlated with any clearly visible solar wind variation. The observations presented here serve as an introduction to a complex event with numerous opportunities for future, more in-depth studies.

Keywords: solar energetic particles; solar coronal mass ejection shocks; heliosphere
Impact of the Collision Model on the Multi-messenger Emission from Gamma-Ray Burst Internal Shocks

We discuss the production of multiple astrophysical messengers (neutrinos, cosmic rays, gamma-rays) in the Gamma-Ray Burst (GRB) internal shock scenario, focusing on the impact of the collision dynamics between two shells on the fireball evolution. In addition to the inelastic case, in which plasma shells merge when they collide, we study the Ultra Efficient Shock scenario, in which a fraction of the internal energy is re-converted into kinetic energy and, consequently, the two shells survive and remain in the system. We find that in all cases, a quasi-diffuse neutrino flux from GRBs at the level of 10-11- ${10}^{-10}\,\mathrm{GeV}\,{\mathrm{cm}}^{-2}\,{{\rm{s}}}^{-1}\,{\mathrm{sr}}^{-1}$ (per flavor) is expected for protons and a baryonic loading of 10, which is potentially within the reach of IceCube-Gen2. The highest impact of the collision model for multi-messenger production is observed for the Ultra Efficient Shock scenario, that promises high conversion efficiencies from kinetic to radiated energy. However, the assumption that the plasma shells separate after a collision and survive as separate shells within the fireball is found to be justified too rarely in a multicollision model that uses hydrodynamical simulations with the PLUTO code for individual shell collisions.

Keywords: gamma-ray bursts; cosmic ray sources; ultra-high-energy cosmic radiation; high energy astrophysics
TESS Observations of Outbursts on Polars—Superflares

Flare events are magnetic activities on the stellar surface, which can provide us with information about the accretion behavior and evolution of polars. In this paper, we search for flare events on polars from all the available 2 minute cadence TESS data through visual inspection, and identify six flare events on five flaring stars from 185 polars. All the flares have bolometric energies above 1034 erg, with a median of ∼1035 erg, so they are superflares. Among them, two flares are followed by a brightness enhancement, which may suggest an accretion burst on the white dwarf caused by a coronal mass ejection. A completeness analysis of the detections demonstrates that the flare activities on the low-mass red dwarfs of polars are very similar to those on M dwarfs, which indicates that the highly magnetic fields of the white dwarfs have no significant effect on the magnetic activities on polars. We estimate that another ∼20–30 polars include a magnetically active secondary star, and more intensive searching for flares on polars is encouraged in further work.

Keywords: am herculis stars; m dwarf stars; magnetic stars
First JWST Observations of JAGB Stars in the SN Ia Host Galaxies: NGC 7250, NGC 4536, NGC 3972

The J-region Asymptotic Giant Branch (JAGB) method is a standard candle that leverages the constant luminosities of color-selected, carbon-rich AGB stars, measured in the near-infrared at 1.2 μm. The Chicago-Carnegie Hubble Program has obtained JWST imaging of the SN Ia host galaxies NGC 7250, NGC 4536, and NGC 3972. With these observations, the JAGB method can be studied for the first time using JWST. Lee et al. demonstrated the JAGB magnitude is optimally measured in the outer disks of galaxies, because in the inner regions the JAGB magnitude can vary significantly due to a confluence of reddening, blending, and crowding effects. However, determining where the "outer disk" lies can be subjective. Therefore, we introduce a novel method for systematically selecting the outer disk. In a given galaxy, the JAGB magnitude is first separately measured in concentric regions, and the "outer disk" is then defined as the first radial bin where the JAGB magnitude stabilizes to a few hundredths of a magnitude. After successfully employing this method in our JWST galaxy sample, we find the JAGB stars are well segregated from other stellar populations in color-magnitude space, and have observed dispersions about their individual F115W modes of σ N7250 = 0.32 mag, σ N4536 = 0.34 mag, and σ N3972 = 0.35 mag. These measured dispersions are similar to the scatter measured for the JAGB stars in the LMC using 2MASS data (σ = 0.33 mag). In conclusion, the JAGB stars as observed with JWST clearly demonstrate their considerable power both as high-precision extragalactic distance indicators and as SN Ia supernova calibrators.

Keywords: observational cosmology; distance indicators; asymptotic giant branch stars; carbon stars; galaxy distances; james webb space telescope
Searching for Cataclysmic Variable Stars in Unidentified X-Ray Sources

We carry out a photometric search for new cataclysmic variable stars (CVs), with the goal of identification for candidates of AR Scorpii-type binary systems. We select GAIA sources that are likely associated with unidentified X-ray sources, and analyze the light curves taken by the Zwicky Transient Facility, Transiting Exoplanet Survey Satellite, and Lulin One-meter Telescope in Taiwan. We investigate eight sources as candidates for CVs, among which six sources are new identifications. Another two sources have been recognized as CVs in previous studies, but no detailed investigations have been done. We identify two eclipsing systems that are associated with an unidentified XMM-Newton or Swift source, and one promising candidate for polar associated with an unidentified ASKA source. Two polar candidates may locate in the so-called period gap of a CV, and the other six candidates have an orbital period shorter than that of the period gap. Although we do not identify a promising candidate for AR Scorpii-type binary systems, our study suggests that CV systems that have X-ray emission and do not show frequent outbursts may have been missed in previous surveys.

Keywords: white dwarf stars; binary stars; cataclysmic variable stars; observatories