adsabs/SciX_UAT_keywords huggingface dataset:
Signature of High-amplitude Pulsations in Seven δ Sct Stars via TESS Observations

The regular behavior of the pulsations of high-amplitude δ Sct (HADS) stars gives a greater chance to investigate the interiors of stars. We analyzed seven HADS stars showing peak-to-peak amplitudes of more than 0.3 mag that were newly observed by TESS. We obtained that TIC 374753270, TIC 710783, and TIC 187386415 pulsate in fundamental radial mode; also, TIC 130474019 and TIC 160120432 show double radial modes. On the other hand, TIC 148357344 and TIC 278119167 demonstrate triple-mode behavior. Our analysis shows that these seven stars are close to the red edge of the (inside) instability strip in the Hertzsprung–Russell diagram. The fundamental mode of these seven targets follows the period–luminosity (PL) relation for δ Sct stars. However, TIC 278119167 deviates slightly from the fundamental PL relation. The double-mode and triple-mode HADS stars (TIC 130474019, TIC 160120432, TIC 148357344, and TIC 278119167) are in agreement with the period ratio ranges (fundamental to first and second overtones). Using the information of 176 HADS stars (Netzel and Smolec), we find a scaling relation ( )) between the metallicity ([Fe/H]) and mass (M), luminosity (L), effective temperature (T eff), and the fundamental period (P0). We estimate the metallicity of the seven newly identified HADS stars ranging from ‑0.62 to 0.37 dex.

Keywords: asteroseismology; stellar oscillations; delta scuti variable stars
Stellar Inclination Angles from Be-star Hα Emission Line Profiles

We demonstrate that the angle between a star's rotation axis and the observer's line of sight, usually called the inclination angle, can be reliably determined for Be stars via Hα emission line profile fitting. We test our method on a sample of 11 Be stars with available long-baseline interferometric data from the Navy Precision Optical Interferometer. We fit the Hα emission line profile of each star to obtain a spectroscopic inclination angle IHα. We then obtain an independent inclination angle estimate, ${I}_{{{\rm{V}}}^{2}}$ , by fitting the observed interferometric visibilities with model visibilities based on a purely geometric representation of the light distribution on the sky. The sample differences, ${\rm{\Delta }}I\equiv {I}_{{\rm{H}}\alpha }-{I}_{{{\rm{V}}}^{2}}$ , are normally distributed with a mean of zero and a standard deviation of 6°7, and the linear correlation coefficient between IHα and ${I}_{{{\rm{V}}}^{2}}$ is r = 0.93. As Be stars comprise upwards of one-fifth of all main-sequence B-type stars, this Hα line profile fitting technique has the potential to provide an efficient method for detecting correlated stellar spin axes in young open clusters. Furthermore, if the orientation of the Be star's circumstellar disk on the plane of the sky can be constrained by polarization measurements, it is possible to determine the full 3D stellar rotation vector of each Be star.

Keywords: early-type emission stars; be stars; circumstellar disks; fundamental parameters of stars
Upper Limits on the Escape of Volatiles from (486958) Arrokoth Using New Horizons Alice Ultraviolet Spectrograph Observations

During the New Horizons flyby of Kuiper Belt object (486958) Arrokoth on 2019 January 1, a search was made for escaping volatiles. Using the Alice spectrograph, appulse observations of both the Sun and the star HD42954 were performed to look for signatures of far-ultraviolet absorption by various species. No escaping volatiles were detected, and in this article we present upper limits to the escape rates for several species using a Haser model for the maximum line-of-sight column densities that would be undetected at 3σ. These results are useful for models for the formation and evolution of Kuiper Belt objects.

Keywords: classical kuiper belt objects; neutral coma gases
The Formation Process of the First Halo Coronal Mass Ejection in Solar Cycle 25: Magnetic Cancellation, Bidirectional Jet, and Hot Channel

To better understand the trigger mechanism of a coronal mass ejection (CME), we present the evolution of a CME source region (active region NOAA 12790) and the formation of a hot channel before the occurrence of the first halo CME in solar cycle 25. Through analyzing the evolution of Solar Dynamics Observatory/Helioseismic and Magnetic Imager line-of-sight magnetograms, it is found that continuous magnetic cancellation occurs at the polarity inversion line (PIL) in this active region. With ongoing magnetic cancellation, several bidirectional jets and unidirectional jets occur along the large-scale arched magnetic loops. A hot channel forms during the first bidirectional jet. After the occurrence of the fourth bidirectional jet, the hot channel immediately erupts and produces a C-class flare, a cusp structure, and a halo CME. It is worth pointing out that the cusp structure only appears in the 131 Å and 94 Å observations (temperature about 10 MK). The obvious contraction of the newly formed loops is observed at the top of the cusp structure. The observations reveal a clear physics process: magnetic cancellation of a bipolar magnetic field at the PIL results in the occurrence of the bidirectional/unidirectional jets and the formation of the hot channel. The axial magnetic flux feeding for the hot channel through the continued magnetic cancellation leads to the hot channel eruption, which results in the formation of the hot cusp structure and the occurrence of the C-class flare and the halo CME.

Keywords: solar activity; solar coronal mass ejections; jets; magnetic fields; solar magnetic reconnection; solar filament eruptions; solar photosphere
Insight-HXMT Observations of a Possible Fast Transition from the Jet- to Wind-dominated State during a Huge Flare of GRS 1915+105

We present the analysis of the brightest flare that was recorded in the Insight-HMXT data set in a broad energy range (2-200 keV) from the microquasar GRS 1915+105 during an unusual low-luminosity state. This flare was detected by Insight-HXMT among a series of flares during 2019 June 2 UTC 16:37:06-20:11:36 with a 2-200 keV luminosity of 3.4-7.27 × 1038 erg s-1. Basing on the broadband spectral analysis, we find that the flare spectrum shows different behaviors during bright and faint epochs. The spectrum of the flare can be fitted with a model dominated by a power-law component. Additional components show up in the bright epoch with a hard tail and in the faint epoch with an absorption line of ∼6.78 keV. The reflection component of the latter is consistent with an inner disk radius ∼five times larger than that of the former. These results on the giant flare during the "unusual" low-luminosity state of GRS 1915+105 may suggest that the source experiences a possible fast transition from a jet-dominated state to a wind-dominated state. We speculate that the evolving accretion disk and the large-scale magnetic field may play important roles in this peculiar huge flare.

Keywords: black holes; x-ray binary stars; relativistic jets; accretion; magnetic fields
Modeling the Spectral Energy Distribution of the Active Galactic Nucleus inside NGC 4395

We study the broadband spectral energy distribution (SED) of the prototypical low-mass active galactic nucleus (AGN) in NGC 4395. We jointly model the optical through mid-IR SED with a combination of galaxy and AGN light, and find that on arcsecond scales the AGN dominates at most wavelengths. However, there is still some ambiguity about emission from the galaxy, owing partially to the strong short-term variability of the black hole. We investigate the use of smooth- and clumpy-torus models in order to disentangle the nuclear IR emission, as well as exploring the use of poloidal wind emission to account for the blue spectral slope observed in the near-IR. Even when simultaneously fitting the full optical-IR spectral range, we find that degeneracies still remain in the best-fit models. We conclude that high-spatial-resolution and wider-wavelength coverage with the JWST is needed to understand the mid-IR emission in this complex, highly variable object, which is the best nearby example to provide a blueprint to finding other low-mass AGNs via their mid-IR emission in the future.

Keywords: active galactic nuclei; intermediate-mass black holes; spectral energy distribution
Stellar Mass-to-light Ratios: Composite Bulge+Disk Models and the Baryonic Tully-Fisher Relation

We present stellar population models to calculate the mass-to-light ratio (ϒ*) based on galaxies' colors ranging from GALEX far-UV to Spitzer IRAC1 at 3.6 μm. We present a new composite bulge+disk ϒ* model that considers the varying contribution from bulges and disks based on their optical and near-IR colors. Using these colors, we build plausible star formation histories and chemical enrichment scenarios based on the star formation rate-stellar mass and mass-metallicity correlations for star-forming galaxies. The most accurate prescription is to use the actual colors for the bulge and disk components to constrain ϒ*; however, a reasonable bulge+disk model plus total color only introduces 5% more uncertainty. Full bulge+disk ϒ* prescriptions applied to the baryonic Tully-Fisher relation improve the linearity of the correlation, increase the slope, and reduce the total scatter by 4%.

Keywords: galaxy stellar content; galaxy kinematics
Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

In order to constrain the size of the optical continuum emission region in the dwarf Seyfert 1 galaxy NGC 4395 through reverberation mapping, we carried out high-cadence photometric monitoring in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at Haleakalā Observatory. Correlated variability across the griz bands is clearly detected, and the r-, i-, and z-band light curves show lags of ${7.72}_{-1.09}^{+1.01}$ , ${14.16}_{-1.25}^{+1.22}$ , and ${20.78}_{-2.09}^{+1.99}$ minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lag-wavelength relationship is consistent with the τ ∝ λ 4/3 dependence found for more luminous active galactic nuclei. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as τ gz ∝ L 0.56±0.05, similar to the scaling of broad-line region size with luminosity, reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.

Keywords: reverberation mapping; seyfert galaxies
Investigating the Physical Conditions in Extended System Hosting Mid-infrared Bubble N14

To observationally explore physical processes, we present a multiwavelength study of a wide-scale environment toward l = 13°7-14°9 containing a mid-infrared bubble N14. The analysis of 12CO, 13CO, and C18O gas at [31.6, 46] km s-1 reveals an extended physical system (extension ∼59 pc × 29 pc), which hosts at least five groups of the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) 870 μm dust clumps at d ∼3.1 kpc. These spatially distinct groups/subregions contain unstable molecular clumps and are associated with several Class I young stellar objects (mean age ∼0.44 Myr). At least three groups of ATLASGAL clumps associated with the expanding H II regions (including the bubble N14) and embedded infrared dark clouds, devoid of the ionized gas, are found in the system. The observed spectral indices derived using the Giant Metrewave Radio Telescope (GMRT) and THOR radio continuum data suggest the presence of nonthermal emission with the H II regions. The high-resolution GMRT radio continuum map at 1280 MHz traces several ionized clumps powered by massive B-type stars toward N14, which are considerably young (age ∼103-104 yr). Locally, the early stage of star formation is evident toward all the groups of clumps. The position-velocity maps of 12CO, 13CO, and C18O exhibit an oscillatory-like velocity pattern toward the selected longitude range. Considering the presence of different groups/subregions in the system, the oscillatory pattern in velocity is indicative of the fragmentation process. All these observed findings favor the applicability of the global collapse scenario in the extended physical system, which also seems to explain the observed hierarchy.

Keywords: h ii regions; interstellar medium; star formation; pre-main sequence stars
Figuring Out Gas & Galaxies in Enzo (FOGGIE). IV. The Stochasticity of Ram Pressure Stripping in Galactic Halos

We study ram pressure stripping in simulated Milky Way-like halos at $z\geqslant 2$ from the Figuring Out Gas & Galaxies in Enzo (FOGGIE) project. These simulations reach subkiloparsec resolution throughout the gas in their circumgalactic medium (CGM) owing to FOGGIE's novel refinement scheme. The CGM of each halo spans a wide dynamic range in density and velocity over its volume—roughly 6 dex and 1000 km s-1, respectively—translating into a 5 dex range in ram pressure imparted to interacting satellites. The local ram pressure of the simulated CGM at z = 2 is highly stochastic, owing to kiloparsec-scale variations of the density and velocity fields of the CGM gas. As a result, the efficacy of ram pressure stripping depends strongly on the specific path a satellite takes through the CGM. The ram pressure history of a single satellite is generally unpredictable and not well correlated with its approach vector with respect to the host galaxy. The cumulative impact of ram pressure on the simulated satellites is dominated by only a few short, strong impulses—on average, 90% of the total surface momentum gained through ram pressure is imparted in 20% or less of the total orbital time. These results reveal an erratic mode of ram pressure stripping in Milky Way-like halos at high redshift—one that is not captured by a smooth, spherically averaged hydrostatic model of the circumgalactic medium.

Keywords: galaxies; high-redshift galaxies; galaxy environments
The Effect of Molecular Cloud Properties on the Kinematics of Stars Formed in the Trifid Region

The dynamical states of molecular clouds may affect the properties of the stars they form. In the vicinity of the Trifid Nebula (d = 1180 ± 25 pc), the main star cluster (Trifid Main) lies within an expanding section of the molecular cloud; however, ~0.°3 to the north (Trifid North), the cloud's velocity structure is more tranquil. We acquired a Chandra X-ray observation to identify pre-main-sequence stars in Trifid North, complementing a previous observation of Trifid Main. In Trifid North, we identified 51 candidate pre-main-sequence stars, of which 13 are high-confidence Trifid members based on Gaia EDR3 parallaxes and proper motions. We also reanalyzed the membership of Trifid Main and separated out multiple background stellar associations. Trifid North represents a stellar population ~10% as rich as Trifid Main that formed in a separate part of the cloud. The 1D stellar velocity dispersion in Trifid North (0.6 ± 0.2 km s-1) is 3 times lower than that in Trifid Main (1.9 ± 0.2 km s-1). Furthermore, in Trifid Main, proper motions indicate that the portion of the star cluster superimposed on the optical nebula is expanding. Expansion of the H II region around the O-star HD 164492A, and the resulting gas expulsion, can explain both the motions of the stars and gas in Trifid Main. Contrary to previous studies, we find no evidence that a cloud-cloud collision triggered star formation in the region.

Keywords: astrometry; giant molecular clouds; star formation; stellar kinematics; x-ray astronomy
The Main Sequence View of Quasars Accreting at High Rates: Influence of Star Formation

Highly accreting quasars show fairly distinctive properties in their optical, UV, and X spectra, and are easy to recognize because of their specific location in the quasar main sequence: they are the strongest optical FeII emitters. They show a surprisingly high rate of radio detections and, at variance with the classical radio-loud (jetted) sources, the origin of their radio emission is probably "thermal." The chemical composition of the broad line emitting gas implies high metallicity values, above 10 times solar. A fraction of highly accreting quasars at intermediate and high redshift might therefore be in a particular evolutionary stage that is unobscured albeit still involving a contribution of nuclear and circum-nuclear star formation in their multifrequency properties. * Contribution presented at the 237th meeting of the AAS.

Keywords: active galactic nuclei
Outer Solar System Perihelion Gap Formation through Interactions with a Hypothetical Distant Giant Planet

Among the outer solar system minor planet orbits there is an observed gap in perihelion between roughly 50 and 65 au at eccentricities e ≳ 0.65. Through a suite of observational simulations, we show that the gap arises from two separate populations, the Extreme Trans-Neptunian Objects (ETNOs; perihelia q ≳ 40 au and semimajor axes a ≳ 150 au) and the Inner Oort Cloud objects (IOCs; q ≳ 65 au and a ≳ 250 au), and is very unlikely to result from a realistic single, continuous distribution of objects. We also explore the connection between the perihelion gap and a hypothetical distant giant planet, often referred to as Planet 9 or Planet X, using dynamical simulations. Some simulations containing Planet X produce the ETNOs, the IOCs, and the perihelion gap from a simple Kuiper-Belt-like initial particle distribution over the age of the solar system. The gap forms as particles scattered to high eccentricity by Neptune are captured into secular resonances with Planet X where they cross the gap and oscillate in perihelion and eccentricity over hundreds of kiloyears. Many of these objects reach a minimum perihelia in their oscillation cycle within the IOC region increasing the mean residence time of the IOC region by a factor of approximately five over the gap region. Our findings imply that, in the presence of a massive external perturber, objects within the perihelion gap will be discovered, but that they will be only ~20% as numerous as the nearby IOC population (65 au ≲ q ≲ 100 au).

Keywords: trans-neptunian objects; planetary theory; detached objects; oort cloud objects; celestial mechanics; solar system astronomy
X-Ray Polarization Observations of BL Lacertae

Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus that the synchrotron emission is responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae (BL Lac) performed with the Imaging X-ray Polarimetry Explorer, from which an upper limit to the polarization degree Π X < 12.6% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton-synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac.

Keywords: relativistic jets; x-ray active galactic nuclei; active galactic nuclei; blazars; spectropolarimetry
Two-moment Neutrino Flavor Transformation with Applications to the Fast Flavor Instability in Neutron Star Mergers

Multi-messenger astrophysics has produced a wealth of data with much more to come in the future. This enormous data set will reveal new insights into the physics of core-collapse supernovae, neutron star mergers, and many other objects where it is actually possible, if not probable, that new physics is in operation. To tease out different possibilities, we will need to analyze signals from photons, neutrinos, gravitational waves, and chemical elements. This task is made all the more difficult when it is necessary to evolve the neutrino component of the radiation field and associated quantum-mechanical property of flavor in order to model the astrophysical system of interest—a numerical challenge that has not been addressed to this day. In this work, we take a step in this direction by adopting the technique of angular-integrated moments with a truncated tower of dynamical equations and a closure, convolving the flavor-transformation with spatial transport to evolve the neutrino radiation quantum field. We show that moments capture the dynamical features of fast flavor instabilities in a variety of systems, although our technique is by no means a universal blueprint for solving fast flavor transformation. To evaluate the effectiveness of our moment results, we compare to a more precise particle-in-cell method. Based on our results, we propose areas for improvement and application to complementary techniques in the future.

Keywords: neutrino decoupling; supernova neutrinos; neutron stars
Time-lag Between Disk and Corona Radiation Leads to Hysteresis Effect Observed in Black hole X-Ray Binary MAXI J1348-630

Accretion is an essential physical process in black hole X-ray binaries (BHXRBs) and active galactic nuclei. The properties of accretion flows and their radiation were originally considered to be uniquely determined by the mass accretion rate of the disk; however, the "hysteresis effect" observed during outbursts of nearly all BHXRBs seriously challenges this paradigm. The hysteresis effect referred to is that the hard-to-soft state transition in the fast-rise stage occurs at much higher luminosity than the soft-to-hard state transition in the slow-decay stage. That is, the same source can show different spectral/temporal properties at the same luminosity. Phenomenologically, this effect is also represented as the so-called "q"-shaped hardness-intensity diagram, which has been proposed as a unified scene for BHXRBs. However, there is still a lack of quantitative theoretical interpretation and observational understanding of the "q"-diagram. Here, we present a detailed time-lag analysis of a recently found BHXRB, MAXI J1348-630, intensively monitored by Insight-HXMT over a broad energy band (1-150 keV). We find the first observational evidence that the observed time-lag between radiations of the accretion disk and the corona leads naturally to the hysteresis effect and the "q"-diagram. Moreover, complemented by the quasi-simultaneous Swift data, we achieve a panorama of the accretion flow: the hard X-ray outburst from the corona heats and subsequently induces the optical brightening in the outer disk with nearly no lag; thereafter, the enhanced accretion in the outer disk propagates inward, generating the delayed soft X-ray outburst at the viscous timescale of ~8-12 days.

Keywords: accretion; low-mass x-ray binary stars; black hole physics