adsabs/SciX_UAT_keywords huggingface dataset:
X-Ray Studies of Blazar 1ES 1959+650 Using Swift and XMM-Newton Satellite

High synchrotron energy peaked blazar 1ES 1959+650 was studied with the Swift and XMM-Newton satellites in a total of 127 observations during the period 2018 June-2020 December. We extensively studied its flux and spectral variability on intraday and long-term timescales. Discrete correlation function analysis between soft and hard X-ray bands indicates soft as well as hard lags. The results were used to constrain the magnetic field of the emitting region, which was found to be 0.64 ± 0.05 G. On long-term timescales, the distribution of fluxes shows lognormal behavior, which could be attributed to the minijets-in-a-jet model or might be due to the propagation of relativistic shocks down the jet. The spectral energy distribution around the synchrotron peak is well described by the log-parabola model. Spectral parameters like the peak energy E p , curvature β, and peak luminosity L p were derived from spectral analysis. Their correlations were studied to constrain the acceleration processes of the emitting particles. E p shows strong correlation with L p during the high state of the source, which indicates spectral changes might be caused by the variations of the average electron energy. Low values of the curvature parameter β and a weak correlation between E p and β indicate the coexistence of stochastic/statistical acceleration of electrons in the emitting region. Implications of other results are also discussed.

Keywords: active galactic nuclei; blazars; bl lacertae objects; relativistic jets
Ross 19B: An Extremely Cold Companion Discovered via the Backyard Worlds: Planet 9 Citizen Science Project

Through the Backyard Worlds: Planet 9 citizen science project, we have identified a wide-separation (~10', ~9900 au projected) substellar companion to the nearby (~17.5 pc), mid-M dwarf Ross 19. We have developed a new formalism for determining chance alignment probabilities based on the BANYAN Σ tool, and find a 100% probability that this is a physically associated pair. Through a detailed examination of Ross 19A, we find that the system is metal-poor ([Fe/H] = -0.40 ± 0.12) with an age of ${7.2}_{-3.6}^{+3.8}$ Gyr. Combining new and existing photometry and astrometry, we find that Ross 19B is one of the coldest known wide-separation companions, with a spectral type on the T/Y boundary, an effective temperature of ${500}_{-100}^{+115}$ K, and a mass in the range 15-40 MJup. This new, extremely cold benchmark companion is a compelling target for detailed characterization with future spectroscopic observations using facilities such as the Hubble Space Telescope or James Webb Space Telescope.

Keywords: brown dwarfs; low mass stars
Spatial Variations and Breaks in the Optical–Near-infrared Spectra of the Pulsar and Pulsar Wind Nebula in Supernova Remnant 0540–69.3

The supernova remnant (SNR) 0540–69.3, twin of the Crab Nebula, offers an excellent opportunity to study the continuum emission from a young pulsar and pulsar wind nebula (PWN). We present observations taken with the Very Large Telescope instruments MUSE and X-shooter in the wavelength range 3000–25000 Å, which allow us to study spatial variations of the optical spectra, along with the first near-infrared (NIR) spectrum of the source. We model the optical spectra with a power law (PL) F ν ∝ ν ‑α and find clear spatial variations (including a torus–jet structure) in the spectral index across the PWN. Generally, we find spectral hardening toward the outer parts, from α ∼ 1.1 to ∼0.1, which may indicate particle reacceleration by the PWN shock at the inner edge of the ejecta or alternatively time variability of the pulsar wind. The optical–NIR spectrum of the PWN is best described by a broken PL, confirming that several breaks are needed to model the full spectral energy distribution of the PWN, and suggesting the presence of more than one particle population. Finally, subtracting the PWN contribution from the pulsar spectrum we find that the spectrum is best described with a broken-PL model with a flat and a positive spectral index, in contrast to the Crab pulsar that has a negative spectral index and no break in the optical. This might imply that pulsar differences propagate to the PWN spectra.

Keywords: core-collapse supernovae; supernova remnants; pulsar wind nebulae; pulsars
Hanle Effect with Angle-dependent Partial Frequency Redistribution in Three-dimensional Media

There has been a constant improvement in the observational measurement of linear polarization in chromospheric spectral lines in the last three decades. However, modeling polarized profiles of these lines still remains incomplete, due to the lack of inclusion of fundamental physics in modeling efforts. To model the observed solar spectrum and its linear polarization, we need a solution to the polarized radiative transfer equation. The polarization in strong resonance lines originates from the scattering mechanism known as the partial frequency redistribution (PFR) of an anisotropic radiation field. The understanding of the linear polarization in spatially resolved structures needs radiative transfer solutions in multidimensional geometries. In this paper, we explore the effects of angle-dependent PFR on scattering polarization profiles formed in three-dimensional (3D) media. We find that the 3D geometry combined with angle-dependent PFR produces more scattering polarization than an angle-averaged one.

Keywords: radiative transfer; solar atmosphere; magnetic fields
A Search for Transits among the Delta Scuti Variables in Kepler

We search for transits around all known pulsating δ Sct variables (6500 K < Teff < 10,000 K) in the long-cadence Kepler data after subtracting the pulsation signal through an automated routine. To achieve this, we devise a simple and computationally inexpensive method for distinguishing between low-frequency pulsations and transits in light curves. We find three new candidate transit events that were previously hidden behind the pulsations, but caution that they are likely to be false positive events. We also examined the Kepler Objects of Interest catalog and identify 13 additional host stars that show δ Sct pulsations. For each star in our sample, we use the nondetection of pulsation timing variations for a planet that is known to be transiting a δ Sct variable to obtain both an upper limit on the mass of the planet and the expected radial velocity semi-amplitude of the host star. Simple injection tests of our pipeline imply 100% recovery for planets of 0.5 RJup or greater. Extrapolating our number of Kepler δ Sct stars, we expect 12 detectable planets above 0.5 RJup in TESS. Our sample contains some of the hottest known transiting planets around evolved stars, and is the first complete sample of transits around δ Sct variables. We make available our code and pulsation-subtracted light curves to facilitate further analysis (https://github.com/danhey/dsct-exoplanet).

Keywords: delta scuti variable stars; exoplanet detection methods; exoplanet astronomy
Angular Momentum Variation of the Milky Way Thick Disk: The Dependence of Chemical Abundance and Evidence of the Inside-out Formation Scenario

We investigate the angular momentum of mono-abundance populations (MAPs) of the Milky Way thick disk by using a sample of 26,076 giant stars taken from APOGEE Data Release (DR) 17 and Gaia early DR3. The vertical and perpendicular angular momentum components, L Z and L P , of the MAPs in narrow bins have significant variations across the [α/M]-[M/H] plane. L Z and L P systematically change with [M/H] and [α/M] and can be alternatively quantified by the chemical gradients: d[M/H]/dL Z = 1.2 × 10-3 dex kpc-1 km-1 s, d[M/H]/dL P = -5.0 × 10-3 dec kpc-1 km-1 s, and d[α/M]/dL Z = -3.0 × 10-4 dex kpc-1 km-1 s, d[α/M]/dL P = 1.2 × 10-3 dec kpc-1 km-1 s. These correlations can also be explained as the chemical dependence of the spatial distribution shape of the MAPs. We also exhibit the corresponding age dependence of the angular momentum components. Under the assumption that the guiding radius (R g ) is proportional to L Z , this provides direct observational evidence of the inside-out structure formation scenario of the thick disk, with dR g /dAge = -1.9 kpc Gyr-1. The progressive changes in the disk thickness can be explained by the upside-down formation or/and the consequent kinematical heating.

Keywords: milky way disk; milky way evolution; stellar kinematics; dynamical evolution; galaxy structure; astronomy data analysis; chemical abundances
Crepuscular Rays from the Highly Inclined Active Galactic Nucleus in IC 5063

On Earth near sunset, the Sun may cast "crepuscular rays" such that clouds near the horizon obscure the origin of light scattered in bright rays. In principle, active galactic nuclei (AGN) should be able to produce similar effects. Using new Hubble Space Telescope (HST) near-infrared and optical observations, we show that the active galaxy IC 5063 contains broad radial rays extending to ≳11 kpc from the nucleus. We argue that the bright rays may arise from dusty scattering of continuum emission from the active nucleus, while the dark rays are due to shadowing near the nucleus, possibly by a warped torus. We also consider alternative AGN-related and stellar origins for the extended light. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with programs #15444 and #15609.

Keywords: agn host galaxies; interstellar dust; interstellar scattering; galaxy mergers; galaxy winds; galaxy classification systems
The Multipolar Magnetic Field of the Millisecond Pulsar PSR J0030+0451

Modeling of the NICER X-ray waveform of the pulsar PSR J0030+0451, aimed at constraining the neutron star mass and radius, has inferred surface hot spots (the magnetic polar caps) that imply significantly nondipolar magnetic fields. To this end, we investigate magnetic field configurations that comprise offset dipole-plus-quadrupole components using a static vacuum field and force-free global magnetosphere models. Taking into account the compactness and observer angle values provided by Miller et al. and Riley et al., we compute geodesics from the observer plane to the polar caps to compute the resulting X-ray light curve. We explore, through Markov Chain Monte Carlo techniques, the detailed magnetic field configurations that can reproduce the observed X-ray light curve and have discovered degeneracies, i.e., diverse field configurations, which can provide sufficient descriptions of the NICER X-ray waveforms. Having obtained the force-free field structures, we then compute the corresponding synchronous γ-ray light curves following Kalapotharakos et al.; these we compare to those obtained by Fermi-LAT, to provide models consistent with both the X-ray and the γ-ray data, thereby restricting further the multipole field parameters. An essential aspect of this approach is the proper computation of the relative phase between the synchronous X- and γ-ray light curves. We conclude with a discussion of the broader implications of our study.

Keywords: pulsars; millisecond pulsars; x-ray astronomy; gamma-ray astronomy; stellar magnetic fields; markov chain monte carlo; general relativity; space telescopes
Coronal Wave Trains and Plasma Heating Triggered by Turbulence in the Wake of a CME

Magnetohydrodynamic (MHD) turbulence plays an important role for the fast energy release and wave structures related to coronal mass ejections (CMEs). The CME plasma has been observed to be strongly heated during solar eruptions, but the heating mechanism is not understood. In this paper, we focus on the hot, dense region at the bottom of the CME and the generation of coronal wave trains therein using a high-resolution 2.5D MHD simulation. Our results show that the interaction between the tearing current sheet and the turbulence, including the termination shocks (TSs) at the bottom of the CME, can make a significant contribution to heating the CME, and the heating rate in this region is found to be greater than the kinetic energy transfer rate. Also, the turbulence can be somewhat amplified by the TSs. The compression ratio of the TS under the CME can exceed 4 due to thermal conduction, but such a strong TS is hardly detectable in all Solar Dynamics Observatory/Atmospheric Imaging Assembly bands. And turbulence is an indispensable source for the periodic generation of coronal wave trains around the CME.

Keywords: magnetohydrodynamical simulations; solar coronal mass ejections; termination shock; solar extreme ultraviolet emission
Characterizing the Gamma-Ray Emission Properties of the Globular Cluster M5 with the Fermi-LAT

We analyzed the globular cluster M5 (NGC 5904) using 15 yr of gamma-ray data from the Fermi Large Area Telescope (LAT). Using rotation ephemerides generated from Arecibo and FAST radio telescope observations, we searched for gamma-ray pulsations from the seven millisecond pulsars (MSPs) identified in M5. We detected no significant pulsations from any of the individual pulsars. In addition, we searched for possible variations of the gamma-ray emission as a function of orbital phase for all six MSPs in binary systems, but we did not detect any significant modulations. The gamma-ray emission from the direction of M5 is well described by an exponentially cutoff power-law spectral model, although other models cannot be excluded. The phase-averaged emission is consistent with being steady on a timescale of a few months. We estimate the number of MSPs in M5 to be between 1 and 10, using the gamma-ray conversion efficiencies for well-characterized gamma-ray MSPs in the Third Fermi-LAT Catalog of Gamma-ray Pulsars, suggesting that the sample of known MSPs in M5 is (nearly) complete, even if it is not currently possible to rule out a diffuse component of the observed gamma rays from the cluster.

Keywords: globular star clusters; millisecond pulsars; gamma-ray sources
Kinetic-scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere

In this work, we present the first results from the flux angle (FA) operation mode of the Faraday Cup instrument on board the Parker Solar Probe (PSP). The FA mode allows rapid measurements of phase space density fluctuations close to the peak of the proton velocity distribution function with a cadence of 293 Hz. This approach provides an invaluable tool for understanding kinetic-scale turbulence in the solar wind and solar corona. We describe a technique to convert the phase space density fluctuations into vector velocity components and compute several turbulence parameters, such as spectral index, residual energy, and cross helicity during two intervals when the FA mode was used in PSP's first encounter at 0.174 au distance from the Sun.

Keywords: heliosphere; interplanetary turbulence; solar wind; magnetohydrodynamics; alfven waves
The Inner Disk Rim of HD 163296: Linking Radiative Hydrostatic Models with Infrared Interferometry

Previous studies of the protoplanetary disk HD 163296 revealed that the morphology of its sub-au infrared emission encompasses the terminal sublimation front of dust grains, referred to as the inner rim, but also extends into the (supposedly) dust-free region within it. Here, we present a set of radiative hydrostatic simulations of the inner rim in order to assess how much the rim alone can contribute to the observed interferometric visibilities V, half-light radii R hl, and fractional disk fluxes ${ \mathcal F }$ in the wavelength range 1.5–13 μm. In our set of models, we regulate the cooling efficiency of the disk via the boundary condition for radiation diffusion and we also modify the shape of the sublimation front. We find that when the cooling efficiency is reduced, the infrared photosphere at the rim becomes hotter, leading to an increase in R hl sufficient to match the observations. However, the near-infrared disk flux is typically too low ( ${ \mathcal F }\simeq 0.25$ at 1.5 μm), resulting in H-band visibility curves located above the observed data. We show that the match to the H-band observations up to moderate baselines can be improved when a wall-shaped rather than curved sublimation front is considered. Nevertheless, our model visibilities always exhibit a bounce at long baselines, which is not observed, confirming the need for additional emission interior to the rim. In summary, our study illustrates how the temperature structure and geometry of the inner rim need to change in order to boost the rim's infrared emission.

Keywords: protoplanetary disks; planet formation; radiative transfer; interferometry; exoplanets
Dynamical Masses of Young Stars Inferred from Two Transitions of CO with ALMA

Stellar masses are fundamental but often difficult to measure. Thanks to the Atacama Large Millimeter Array (ALMA) and Gaia, dynamical masses of pre-main sequence stars can be precisely measured using the Keplerian rotation of protoplanetary disks. We used ALMA CO(2-1) and CO(3-2) observations of CT Cha and DS Tau to determine their masses by modeling the geometry, kinematics, and physical properties of their disks with a Bayesian-based radiative transfer modeling code (pdspy). We found that the posterior distributions of the masses from the two transitions are inconsistent at the 2-4σ level. These systematic errors may originate from assumptions in the disk model, or perhaps the modest spatial or spectral resolutions used in this study. Regardless, this indicates that dynamical mass measurements using disk kinematics should be treated with caution when using only a single transition line because of these systematic errors.

Keywords: protoplanetary disks; radio interferometry; co line emission
Inspiraling Double Compact Object Detection and Lensing Rate: Forecast for DECIGO and B-DECIGO

Emergence of gravitational wave (GW) astronomy revived the interest in exploring the low-frequency GW spectrum inaccessible from the ground. Satellite GW observatory DECihertz Interferometer Gravitational wave Observatory (DECIGO) in its original configuration and the currently proposed smaller-scale B-DECIGO are aimed to cover the decihertz part of the GW spectrum, which fills the gap between LISA millihertz and deca- to kilohertz range probed by ground-based detectors. In this paper we forecast the detection rates of inspiraling double compact objects (DCOs) and the unresolved confusion noise from these sources in DECIGO and B-DECIGO. In the context of DECIGO we use, for the first time, the population synthesis intrinsic inspiral rates of NS-NS, BH-NS and BH-BH systems. We also estimate the expected gravitational lensing rates of such sources for DECIGO and B-DECIGO. The result is that yearly detection of resolvable DCOs inspirals for the DECIGO is of the order of 102-105, while for a much smaller-scale B-DECIGO they are about 10-105 depending on the DCO population considered. Taking into account that a considerable part of these events would be detectable by ground-based GW observatories, the significance of DECIGO/B-DECIGO could be substantial. Due to contamination by unresolved sources, both DECIGO and B-DECIGO will not be able to register lensed NS-NS or BH-NS systems, but the lensed BH-BH systems could be observed at the rate of about 50 per year in DECIGO. Smaller-scale B-DECIGO will be able to detect a few lensed BH-BH systems per year. We also address the question of the magnification bias in the GW event catalogs of DECIGO and B-DECIGO.

Keywords: gravitational wave detectors; gravitational waves; strong gravitational lensing
Implications for Additional Plasma Heating Driving the Extreme-ultraviolet Late Phase of a Solar Flare with Microwave Imaging Spectroscopy

Extreme-ultraviolet late phase (ELP) refers to the second extreme-ultraviolet (EUV) radiation enhancement observed in certain solar flares, which usually occurs tens of minutes to several hours after the peak of soft X-ray emission. The coronal loop system that hosts the ELP emission is often different from the main flaring arcade, and the enhanced EUV emission therein may imply an additional heating process. However, the origin of the ELP remains rather unclear. Here we present the analysis of a C1.4 flare that features such an ELP, which is also observed in microwave wavelengths by the Expanded Owens Valley Solar Array. Similar to the case of the ELP, we find a gradual microwave enhancement that occurs about 3 minutes after the main impulsive phase microwave peaks. Radio sources coincide with both foot points of the ELP loops and spectral fits on the time-varying microwave spectra demonstrate a clear deviation of the electron distribution from the Maxwellian case, which could result from injected nonthermal electrons or nonuniform heating to the footpoint plasma. We further point out that the delayed microwave enhancement suggests the presence of an additional heating process, which could be responsible for the evaporation of heated plasma that fills the ELP loops, producing the prolonged ELP emission.

Keywords: solar physics; solar radio flares; solar extreme ultraviolet emission
Evidence for Resonance Scattering in the X-Ray Grating Spectrum of the Supernova Remnant N49

Resonance scattering (RS) is an important process in astronomical objects, because it affects measurements of elemental abundances and distorts surface brightness of the object. It is predicted that RS can occur in plasmas of supernova remnants (SNRs). Although several authors reported hints of RS in SNRs, no strong observational evidence has been established so far. We perform a high-resolution X-ray spectroscopy of the SNR N49 with the Reflection Grating Spectrometer on board XMM-Newton. The Reflection Grating Spectrometer spectrum of N49 shows a high G-ratio of O VII Heα lines as well as O VIII Lyβ/α and Fe XVII (3s-2p)/(3d-2p) ratios, which cannot be explained by the emission from a thin thermal plasma. These line ratios can be well explained by the effect of RS. Our result implies that RS has a large impact particularly on a measurement of the oxygen abundance.

Keywords: x-ray sources; supernova remnants; high energy astrophysics; interstellar medium
A Blueprint for the Milky Way's Stellar Populations. V. 3D Local Dust Extinction

Using a grid of empirically calibrated synthetic spectra developed in our previous study, we construct an all-sky 3D extinction map from the large collection of low-resolution XP spectra in Gaia DR3. Along each line of sight, with an area ranging from 0.2 to 13.4 deg2, we determine both the reddening and metallicity of main-sequence stars and model the foreground extinction up to approximately 3 kpc from the Sun. Furthermore, we explore variations in the total-to-selective extinction ratio in our parameter search and identify its mean systematic change across diverse cloud environments in both hemispheres. In regions outside the densest parts of the clouds, our reddening estimates are validated through comparisons with previous reddening maps. However, a notable discrepancy arises in comparison to other independent work based on XP spectra, which can be attributed to systematic offsets in their metallicity estimates. On the other hand, our metallicity scale exhibits reasonable agreement with the high-resolution spectroscopic abundance scale. We also assess the accuracy of the XP spectra by applying our calibrated models, and we confirm an increasing trend of flux overestimation at shorter wavelengths below 400 nm.

Keywords: interstellar dust extinction; stellar abundances; gaia