adsabs/SciX_UAT_keywords huggingface dataset:
Investigating Period Variability Mechanisms in Eclipsing Binary Stars through Eclipsing Time Variation Analysis: A Case Study of TZ Bootis

We present an effective strategy for extensive analysis of eclipsing time variations (ETVs) using modern and sophisticated optimization methods that comprise a set of tools to investigate period variability mechanisms in eclipsing binary stars such as the light-time effect, the Applegate mechanism, and mass transfer. We implement these methods for the first time assuming that the above mechanisms can act simultaneously in the puzzling W UMa-type binary star TZ Bootis by using archival and new TESS data spanning 75 yr and reexamining the up-to-date ETVs. Preliminary analysis of the TESS data revealed for the first time the presence of a second binary in agreement with previous spectroscopic data and astrometric results from Gaia DR3. We consider the most credible scenario for the ETV: two stellar circumbinary companions of minimum masses M 3 = 0.5 M ☉ and M 4 = 0.14 M ☉ in highly eccentric orbits e 3 = 0.70 and e 4 = 0.82 with periods P 3 = 38 yr and P 4 = 20 yr along with a 24 yr magnetic activity of the secondary component and a long-term period increase (dP/dt = 1.2 × 10-8 days yr-1), interpreted as a conservative mass transfer from the secondary to the primary component at a rate of dM 1/dt = 3.7 × 10-9 days yr-1. Further spectroscopic observations, analytical modeling of the second pair, and ETV analysis of both pairs are needed to investigate the quadruple nature of the system.

Keywords: eclipsing binary minima timing method; eclipsing binary stars; w ursae majoris variable stars; computational methods; contact binary stars
Confronting the Magnetar Interpretation of Fast Radio Bursts through Their Host Galaxy Demographics

We explore the millisecond magnetar progenitor scenario in the context of fast radio burst (FRB) host galaxies demographics and offset distributions. Magnetars are neutron stars with strong magnetic fields on the order of 1015 G with a short decay lifetime of less than 104 yr. Due to their extremely short lifetimes, magnetars should follow the demographics of galaxies according to their current star formation rate (SFR). Moreover, we hypothesize that magnetars should follow the SFR profile within galaxies, which we assume to follow an exponential profile. We construct a simple model for the host galaxies of magnetars assuming these events track SFR in all galaxies and compare it to observed properties from a sample of 10 secure FRB hosts. We find the distribution of observed SFRs is inconsistent with the model at >95% c.l. The offset distribution is consistent with this scenario; however, this could be due to the limited sample size and the seeing-limited estimates for the effective radii of the FRB host galaxies. Despite the recent association of an FRB with a magnetar in the Milky Way, magnetars may not be the only source of FRBs in the universe, yet any other successful model must account for the demographics of the FRB host in SFR and their observed galactocentric offsets.

Keywords: radio transient sources; magnetars; transient detection; transient sources; neutron stars
Metallicities of Five z > 5 Emission-line Galaxies in SMACS 0723 Revealed by JWST

JWST's Early Release Observations of the lensing cluster SMACS J0723.3-7327 have given an unprecedented spectroscopic look into the high-redshift universe. These observations reveal five galaxies at z > 5. All five have detectable [O III]λ4363 line emission, indicating that these galaxies have high temperatures and low metallicities and that they are highly star-forming. In recent work, the metallicities of these five galaxies have been studied using various techniques. Here we summarize and compare these previous results, as well as perform our own measurements of the metallicities using improved methodologies that optimize the extraction of the emission lines. In particular, we use simultaneous line fitting and a fixed Balmer decrement correction, as well as a novel footprint measurement of the emission lines in the 2D spectra, to produce higher-fidelity line ratios that are less sensitive to calibration and systematic effects. We then compare our metallicities to those of z ≲ 1 galaxies with high rest-frame equivalent widths of Hβ, finding that they may be good analogs. Finally, we estimate that the JWST galaxies out to z ~ 8 are young compared to the age of the universe.

Keywords: high-redshift galaxies; emission line galaxies; galaxy spectroscopy; metallicity
EMPRESS. XI. SDSS and JWST Search for Local and z 4-5 Extremely Metal-poor Galaxies (EMPGs): Clustering and Chemical Properties of Local EMPGs

We search for local extremely metal-poor galaxies (EMPGs), selecting photometric candidates by broadband color excess and machine-learning techniques with the SDSS photometric data. After removing stellar contaminants by shallow spectroscopy with Seimei and Nayuta telescopes, we confirm that three candidates are EMPGs with 0.05-0.1 Z ⊙ by deep Magellan/MagE spectroscopy for faint [OIII] λ4363 lines. Using a statistical sample consisting of 105 spectroscopically confirmed EMPGs taken from our study and the literature, we calculate the cross-correlation function (CCF) of the EMPGs and all SDSS galaxies to quantify environments of EMPGs. Comparing another CCF of all SDSS galaxies and comparison of SDSS galaxies in the same stellar-mass range (107.0-108.4 M ⊙), we find no significant (>1σ) difference between these two CCFs. We also compare mass-metallicity relations (MZRs) of the EMPGs and those of galaxies at z ~ 0-4 with a steady chemical evolution model and find that the EMPG MZR is comparable with the model prediction on average. These clustering and chemical properties of EMPGs are explained by a scenario of stochastic metal-poor gas accretion on metal-rich galaxies showing metal-poor star formation. Extending the broadband color excess technique to a high-z EMPG search, we select 17 candidates of z ~ 4-5 EMPGs with the deep (≃30 mag) near-infrared JWST/NIRCam images obtained by ERO and ERS programs. We find galaxy candidates with negligible [OIII] λ λ 4959,5007 emission weaker than the local EMPGs and known high-z galaxies, suggesting that some of these candidates may fall in the range of 0-0.01 Z ⊙, which potentially breaks the lowest metallicity limit known to date.

Keywords: galaxy evolution; galaxy chemical evolution; chemical abundances; dwarf galaxies
Detection of GeV Gamma-ray Emission of Kepler's SNR With Fermi-LAT

A likely detection of γ-ray emission from the region of Kepler's Supernova Remnant (SNR) is reported by analyzing ∼12 yr of Pass 8 data of the Fermi Large Area Telescope. Its photon flux is (4.85 ± 0.60) × 10-10 ph cm-2 s-1 with ∼4σ significance in 0.2-500 GeV. Moreover, our results show that there is no significant variability in the light curve of ∼12 yr, and its position can well overlap with the observation result of Chandra in hard X-ray band with a good spatial resolution of 0"5, so the source is likely to be the GeV γ-ray counterpart of Kepler's SNR. The spectral energy distribution of γ-rays from Kepler's SNR favors a hadronic origin in GeV band. Through analyzing multi-band data from radio to γ-ray and surveying the distribution from the surrounding CO molecules cloud, we found that if this γ-ray emission is from Kepler's SNR, then it may originate from interactions between the relativistic protons escaping from the shock of Kepler's SNR and surrounding CO gas molecules. However, more observation data are necessary to firmly confirm the association between the γ-ray source and Kepler's SNR in the future.

Keywords: gamma-rays; non-thermal radiation sources; cosmic rays; supernova remnants; molecular clouds; cosmic ray astronomy; astronomical radiation sources
Radiative Driving of the AGN Outflows in the Narrow-line Seyfert 1 Galaxy NGC 4051

We explore the properties of ionized gas in the nuclear and circumnuclear environment of the narrow-line Seyfert 1 galaxy NGC 4051 using spectroscopic and imaging observations from the Hubble Space Telescope (HST) and Apache Point Observatory's ARC 3.5 m Telescope. We identify an unresolved moderate-density intermediate-width component and a high-density broad component in the optical emission lines from the active nucleus, as well as spatially resolved emission extending up to ~1 kpc in the active galactic nucleus (AGN) ionized narrow-line region (NLR) and ~8 kpc in the stellar ionized host galaxy. The HST narrowband image reveals a distinct conical structure in [O III] emission toward the NE, and the ionized gas kinematics shows up to two blueshifted velocity components, indicating outflows along the edges of a cone. We introduce an improved model of biconical outflow, with our line of sight passing through the wall of the cone, which suggests that the large number of outflowing UV absorbers seen in NGC 4051 are NLR clouds in absorption. Using the deprojection factors from the biconical geometry, we measure true outflow velocities up to 680 km s-1 at a distance of ~350 pc; however, we do not find any rotational signature inside a projected distance of $\leqslant $ 10″ (~800 pc) from the nucleus. We compare the gas kinematics with analytical models based on a radiation-gravity formalism, which show that most of the observed NLR outflows are launched within ~0.5 pc of the nucleus and can travel up to ~1 kpc from this low-luminosity AGN. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program Nos. 8253, 12212. † Based in part on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.

Keywords: active galactic nuclei; seyfert galaxies; galaxy winds; agn host galaxies; active galaxies; supermassive black holes; galaxy kinematics; emission line galaxies
Coronal Mini-jets in an Activated Solar Tornado-like Prominence

High-resolution observations from the Interface Region Imaging Spectrometer reveal the existence of a particular type of small solar jet, which arose singly or in clusters from a tornado-like prominence suspended in the corona. In this study, we perform a detailed statistical analysis of 43 selected mini-jets in the tornado event. Our results show that the mini-jets typically have (1) a projected length of 1.0-6.0 Mm, (2) a width of 0.2-1.0 Mm, (3) a lifetime of 10-50 s, (4) a velocity of 100-350 km s-1, and (5) an acceleration of 3-20 km s-2. Based on spectral diagnostics and EM-Loci analysis, these jets seem to be multithermal small-scale plasma ejections with an estimated average electron density of ∼2.4 × 1010 cm-3 and an approximate mean temperature of ∼2.6 × 105 K. Their mean kinetic energy density, thermal energy density, and dissipated magnetic field strength are roughly estimated to be ∼9 erg cm-3, 3 erg cm-3, and 16 G, respectively. The accelerations of the mini-jets, the UV and EUV brightenings at the footpoints of some mini-jets, and the activation of the host prominence suggest that the tornado mini-jets are probably created by fine-scale external or internal magnetic reconnections (a) between the prominence field and the enveloping or background field or (b) between twisted or braided flux tubes within the prominence. The observations provide insight into the geometry of such reconnection events in the corona and have implications for the structure of the prominence magnetic field and the instability that is responsible for the eruption of prominences and coronal mass ejections.

Keywords: the sun; solar activity; solar prominences
Anticorrelation between the Bulk Speed and the Electron Temperature in the Pristine Solar Wind: First Results from the Parker Solar Probe and Comparison with Helios

We discuss the solar wind electron temperatures Te as measured in the nascent solar wind by Parker Solar Probe during its first perihelion pass. The measurements have been obtained by fitting the high-frequency part of quasi-thermal noise spectra recorded by the Radio Frequency Spectrometer. In addition we compare these measurements with those obtained by the electrostatic analyzer discussed in Halekas et al. These first electron observations show an anticorrelation between Te and the wind bulk speed V: this anticorrelation is most likely the remnant of the well-known mapping observed at 1 au and beyond between the fast wind and its coronal hole sources, where electrons are observed to be cooler than in the quiet corona. We also revisit Helios electron temperature measurements and show, for the first time, that an in situ ( ${T}_{e},V$ ) anticorrelation is well observed at 0.3 au but disappears as the wind expands, evolves, and mixes with different electron temperature gradients for different wind speeds.

Keywords: solar wind
Circular Polarization from Inhomogeneous Synchrotron Sources

Inhomogeneities can influence the polarization emerging from a synchrotron source. However, it is shown that the frequency distribution of circular polarization is only marginally affected, although its magnitude may change substantially. This is used to argue that the observed properties of compact radio sources imply a radiating plasma in which the characteristic waves are nearly circular. As a result, restrictions can be put on the low-energy part of the energy distribution of the relativistic electrons as well as the presence of electron-positron pairs. It is emphasized that this constrains theoretical modeling of the acceleration process for the relativistic electrons; for example, some of the currently popular scenarios seem to need modifications to become consistent with observations.

Keywords: non-thermal radiation sources; radio continuum emission; radio active galactic nuclei; extragalactic radio sources; radiative transfer; radiative transfer equation; radiative processes; active galaxies; radio galaxies; magnetic fields; radio jets; relativistic jets
The Accretion Flow Geometry of MAXI J1820+070 through Broadband Noise Research with Insight Hard X-ray Modulation Telescope

Here we present a detailed study of the broadband noise in the power density spectra of the black hole X-ray binary MAXI J1820+070 during the hard state of its 2018 outburst, using Hard X-ray Modulation Telescope observations. The broadband noise shows two main humps, which might separately correspond to variability from a variable disk and two Comptonization regions. We fitted the two humps with multiple Lorentzian functions and studied the energy-dependent properties of each component up to 90-150 keV and their evolution with spectral changes. The lowest-frequency component is considered as the subharmonic of the quasiperiodic oscillation component and shows a different energy dependence compared with other broadband noise components. We found that although the fractional rms of all the broadband noise components mainly decreases with the energy, their rms spectra are different in shape. Above ~20-30 keV, the characteristic frequencies of these components increase sharply with the energy, meaning that the high-energy component is more variable on short timescales. Our results suggest that the hot inner flow in MAXI J1820+070 is likely to be inhomogeneous. We propose a geometry with a truncated accretion disk and two Comptonization regions.

Keywords: accretion; astrophysical black holes; stellar mass black holes; low-mass x-ray binary stars
Mapping the Complex Kinematic Substructure in the TW Hya Disk

We present ALMA observations of CO J = 2 - 1 and CS J = 5 - 4 emission from the disk around TW Hydrae. Both molecules trace a predominantly Keplerian velocity structure, although a slowing of the rotation velocity is detected at the outer edge of the disk beyond ≈140 au in CO emission. This was attributed to the enhanced pressure support from the gas density taper near the outer edge of the disk. Subtraction of an azimuthally symmetric background velocity structure reveals localized deviations in the gas kinematics traced by each of the molecules. Both CO and CS exhibit a "Doppler flip" feature, centered nearly along the minor axis of the disk (PA ~ 60°) at a radius of 1.″35, coinciding with the large gap observed in scattered light and mm continuum. In addition, the CO emission, both through changes in intensity and its kinematics, traces a tightly wound spiral, previously seen with higher-frequency CO J = 3 - 2 observations. Through comparison with linear models of the spiral wakes generated by embedded planets, we interpret these features in the context of interactions with a Saturn-mass planet within the gap at a position angle of PA = 60°, consistent with the theoretical predictions of Mentiplay et al. The lack of a corresponding spiral in the CS emission is attributed to the strong vertical dependence on the buoyancy spirals, which are believed to only grow in the atmospheric of the disk, rather than those traced by CS emission.

Keywords: protoplanetary disks; exoplanet formation; radio interferometry
On the Capture of Interstellar Objects by Our Solar System

Motivated by recent visits from interstellar comets, along with continuing discoveries of minor bodies in orbit of the Sun, this paper studies the capture of objects on initially hyperbolic orbits by our solar system. Using an ensemble of ∼500 million numerical experiments, this work generalizes previous treatments by calculating the capture cross section as a function of asymptotic speed. The resulting velocity-dependent cross section can then be convolved with any distribution of relative speeds to determine the capture rate for incoming bodies. This convolution is carried out for the usual Maxwellian distribution, as well as the velocity distribution expected for rocky debris ejected from planetary systems. We also construct an analytic description of the capture process that provides an explanation for the functional form of the capture cross section in both the high- and low-velocity limits.

Keywords: dynamical evolution; solar system; small solar system bodies; kuiper belt; oort cloud
Mixed Modes and Asteroseismic Surface Effects. I. Analytic Treatment

Normal-mode oscillation frequencies computed from stellar models differ from those that would be measured from stars with identical interior structures because of modeling errors in the near-surface layers. These frequency differences are referred to as the asteroseismic "surface term." The vast majority of solar-like oscillators that have been observed, and that are expected to be observed in the near future, are evolved stars that exhibit mixed modes. For these evolved stars, the inference of stellar properties from these mode frequencies has been shown to depend on how this surface term is corrected for. We show that existing parameterizations of the surface term account for mode mixing only to first order in perturbation theory, if at all, and therefore may not be adequate for evolved stars. Moreover, existing nonparametric treatments of the surface term do not account for mode mixing. We derive both a first-order construction and a more general approach for one particular class of nonparametric methods. We illustrate the limits of first-order approximations from both analytic considerations and using numerical injection-recovery tests on stellar models. First-order corrections for the surface term are strictly only applicable where the size of the surface term is much smaller than both the coupling strength between the mixed p and g modes, as well as the local g-mode spacing. Our more general matrix construction may be applied to evolved stars, where perturbation theory cannot be relied upon.

Keywords: asteroseismology; stellar oscillations; computational methods; theoretical techniques
Search for Lensing Signatures from the Latest Fast Radio Burst Observations and Constraints on the Abundance of Primordial Black Holes

The possibility that primordial black holes (PBHs) form some part of dark matter has been considered for a long time but poorly constrained over a wide mass range. Fast radio bursts (FRBs) are bright radio transients with millisecond duration. Their lensing effect has been proposed to be one of the cleanest probes for constraining the presence of PBHs in the stellar-mass window. In this paper, we first apply the normalized cross-correlation algorithm to search and identify candidates for lensed FRBs in the latest public FRB observations, i.e., 593 FRBs, which mainly consist of the first Canadian Hydrogen Intensity Mapping Experiment FRB catalog, and then derive constraints on the abundance of PBHs from the null search result of the lensing signature. For a monochromatic mass distribution, the fraction of dark matter made up of PBHs could be constrained to ≤87% for ≥500 M ⊙ at the 95% confidence level by assuming signal-to-noise ratios dependent on the flux ratio threshold for each FRB and that apparently one-off events are intrinsic single bursts. This result would be improved by a factor of 3 when a conventional constant flux ratio threshold is considered. Moreover, we derive constraints on PBHs with a log-normal mass function naturally predicted by some popular inflation models and often investigated with gravitational-wave detections. We find that, in this mass distribution scenario, the constraint from the current public FRB observations is relatively weaker than the one from gravitational-wave detections. It is foreseen that upcoming complementary multimessenger observations will yield considerable constraints on the possibilities of PBHs in this intriguing mass window.

Keywords: radio bursts; strong gravitational lensing; primordial black holes
Probing the Hot Circumgalactic Medium with Broad O VI and X-Rays

Most of the baryonic mass in the circumgalactic medium (CGM) of a spiral galaxy is believed to be warm-hot, with temperature around 106 K. The narrow O VI absorption lines probe a somewhat cooler component at $\mathrm{log}\,T({\rm{K}})=5.5$ , but broad O VI absorbers have the potential to probe the hotter CGM. Here we present 376 ks Chandra LETG observations of a carefully selected galaxy in which the presence of broad O VI together with the non-detection of Lyα was indicative of hot gas. The strongest line expected to be present at ≈106 K is O VII λ21.602. There is a hint of an absorption line at the redshifted wavelength, but the line is not detected with better than 2σ significance. A physical model, taking into account strengths of several other lines, provides better constraints. Our best-fit absorber model has $\mathrm{log}\,T({\rm{K}})=6.3\pm 0.2$ and $\mathrm{log}{N}_{{\rm{H}}}({\mathrm{cm}}^{-2})={20.7}_{-0.5}^{+0.3}$ . These parameters are consistent with the hot plasma model based on UV observations; other O VI models of cooler gas phases are ruled out at better than 99% confidence. Thus we have suggestive, but not conclusive evidence for the broad O VI absorber probing the hot gas from the shallow observations of this pilot program. About 800 ks of XMM-Newton observations will detect the expected absorption lines of O VII and O VIII unequivocally. Future missions like XRISM, Arcus, and Athena will revolutionize the CGM science.

Keywords: circumgalactic medium; galaxy formation; galaxy evolution; x-ray astronomy; warm-hot intergalactic medium; ultraviolet astronomy; x-ray observatories