adsabs/SciX_UAT_keywords huggingface dataset:
A Multiwavelength Light-curve Analysis of the Classical Nova YZ Ret: An Extension of the Universal Decline Law to the Nebular Phase

YZ Ret is the first X-ray flash detected classical nova, and is also observed in optical, X-ray, and gamma-ray. We propose a comprehensive model that explains the observational properties. The white dwarf mass is determined to be ~1.33 M ☉, which reproduces the multiwavelength light curves of YZ Ret, from optical, X-ray, to gamma-ray. We show that a shock is naturally generated far outside the photosphere because winds collide with themselves. The derived lifetime of the shock explains some of the temporal variations of emission lines. The shocked shell significantly contributes to the optical flux in the nebular phase. The decline trend of shell emission in the nebular phase is close to ∝t -1.75 and the same as the universal decline law of classical novae, where t is the time from the outburst.

Keywords: fast novae; classical novae; vy sculpturis stars; x-ray astronomy; high energy astrophysics; shocks; gamma-ray astronomy
Transition Energies and Line Oscillator Strengths of the C 2Π(0)-X 2Π(0-6) Absorption Bands of Nitric Oxide. A Theoretical Study

Theoretical absorption oscillator strengths and wavelengths for rotational transitions of the C 2Π(v' = 0)-X 2Π(v″) bands with v″ = 0-6 of nitric oxide are reported. The Molecular Quantum Defect Orbital method has been used in the calculations and the known interaction between the C 2Π(v = 0) Rydberg and the B 2Π (v = 7) valence states has been dealt with through an appropriate rovibronic energy matrix. We hope that the reported data may be useful in the analysis of the observed ultraviolet nightglow emission from nitric oxide in the upper atmospheres of Earth, Venus, and Mars.

Keywords: molecular spectroscopy; line intensities; line positions
The Distance and Origin of the Cometary Globule CG 12

The cometary globule CG 12 and its associated young cluster NGC 5367 is located at a Galactic latitude of b = 21°, and the origin of this high-latitude star formation event has been unclear. Getman et al. identified a nearby group of B stars and suggested they could be the remnant of a group of massive stars of which one exploded as a supernova. We here use Gaia EDR3 data to measure the accurate distance of NGC 5367 and the B-stars. We find a mean distance of 670 pc for NGC 5367 and 675 pc for the B-stars, strongly supporting the suggestion of Getman et al.

Keywords: star forming regions; star formation; supernovae; molecular clouds
Alignment of Irregular Grains by Radiative Torques: Efficiency Study

We study the efficiency of grain alignment by radiative torques (RATs) for an ensemble of irregular grains. The grains are modeled as ensembles of oblate and prolate spheroids, deformed as Gaussian random ellipsoids, and their scattering interactions are solved using numerically exact methods. We define the fraction of the grains that both rotate fast and demonstrate perfect alignment with grain long axes perpendicular to the magnetic field. We quantify a factor related to the efficacy of alignment and show that it is related to a ${q}_{\max }$ factor of the analytical model of the RAT theory. For the interstellar radiation field, our results indicate that the degree of RAT alignment can reach ∼0.5, which may be sufficient to explain observations even if grains do not have magnetic inclusions.

Keywords: interstellar dust extinction; astrophysical processes; magnetic fields
The Breakthrough Listen Search for Intelligent Life: Observations of 1327 Nearby Stars Over 1.10-3.45 GHz

Breakthrough Listen (BL) is a 10 year initiative to search for signatures of technologically capable life beyond Earth via radio and optical observations of the local universe. A core part of the BL program is a comprehensive survey of 1702 nearby stars at radio wavelengths (1-10 GHz). Here, we report on observations with the 64 m CSIRO Parkes radio telescope in New South Wales, Australia, and the 100 m Robert C. Byrd Green Bank radio telescope in West Virginia, USA. Over 2016 January to 2019 March, a sample of 1138 stars was observed at Green Bank using the 1.10-1.90 GHz and 1.80-2.80 GHz receivers, and 189 stars were observed with Parkes over 2.60-3.45 GHz. We searched these data for the presence of engineered signals with Doppler-acceleration drift rates between ±4 Hz s-1. Here, we detail our data analysis techniques and provide examples of detected events. After excluding events with characteristics consistent with terrestrial radio interference, we are left with zero candidates. That is, we find no evidence of putative radio transmitters above $2.1\times {10}^{12}$ W, and $9.1\times {10}^{12}$ W for Green Bank and Parkes observations, respectively. These observations constitute the most comprehensive search over 1.10-3.45 GHz for technosignatures to date. All data products, totaling ∼219 TB, are available for download as part of the first BL data release (DR1), as described in a companion paper.

Keywords: astrobiology; technosignatures; search for extraterrestrial intelligence
Multiband Transit Follow-up Observations of Five Hot Jupiters with Critical Noise Treatments: Improved Physical Properties

The most challenging limitation in transit photometry arises from the noises in the photometric signal. In particular, the ground-based telescopes are heavily affected by the noise due to perturbation in the Earth's atmosphere. Use of telescopes with large apertures can improve the photometric signal-to-noise ratio to a great extent. However, detecting a transit signal out of a noisy light curve of the host star and precisely estimating the transit parameters call for various noise reduction techniques. Here, we present multiband transit photometric follow-up observations of five hot Jupiters e.g., HAT-P-30 b, HAT-P-54 b, WASP-43 b, TrES-3 b, and XO-2 N b, using the 2 m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle, and the 1.3 m J. C. Bhattacharya Telescope at the Vainu Bappu Observatory, Kavalur. Our critical noise treatment approach includes techniques such as wavelet denoising and Gaussian process regression, which effectively reduce both time-correlated and time-uncorrelated noise components from our transit light curves. In addition to these techniques, use of our state-of-the-art model algorithms have allowed us to estimate the physical properties of the target exoplanets with a better accuracy and precision compared to the previous studies.

Keywords: transit photometry; exoplanets; hot jupiters; wavelet analysis; gaussian processes regression; markov chain monte carlo
An Orbit-flip Mechanism by Eccentric Lidov-Kozai Effect with Stellar Oblateness

Orbit flips have been previously found under the eccentric Lidov-Kozai effect (ELK) in hierarchical three-body systems. Recently, we have found that, in certain conditions, the orbit can flip its orientation in a much different manner, where the stellar oblateness plays an important role. In this paper, orbit-flip behaviors with the ELK effect are investigated as the stellar oblateness varies within a wide range. This is of significance because recent works have shown that the oblateness of young stars has a widespread distribution and may have critical effects on sculpting the final orbital states of close-in planets. Our dynamical model includes the secular potential of the perturber to octupole order and the secular effects of the stellar oblateness. An alignment between the orbit plane of the outer perturber and the stellar bulge is assumed. Our findings mainly consist of two aspects. (i) A new type of orbit-flipping mechanism induced by a combination of the ELK and stellar oblateness effects, referred to as the ELK-J 2 effect, is discovered and confirmed. (ii) We demonstrate that, in the considered aligned configuration, the stellar oblateness suppresses orbit flips due to the ELK effect and produces new flips through the ELK-J 2 effect. Moreover, if the stellar oblateness perturbations are of the same order as the octupole perturbations of the outer perturber, the ELK-induced orbit flips are almost entirely suppressed, while the ELK-J 2 effect reaches its peak for the considered strength of the octupole perturbations. However, from a global view, stellar oblateness always reduces flipping orbits.

Keywords: celestial mechanics; dynamical evolution; perturbation methods; oblateness
Tully-Fisher Distances and Dynamical Mass Constraints for 24 Host Galaxies of Reverberation-mapped AGNs

We present Tully-Fisher distances for 24 active galactic nucleus (AGN) host galaxies with black hole mass (MBH) measurements from reverberation mapping, as well as the first calibration of the V-band Tully-Fisher relation. Combining our measurements of H I 21 cm emission with Hubble Space Telescope and ground-based optical and near-infrared images allows multiple distance measurements for 19 galaxies and single measurements for the remaining 5. Separation of the nucleus from its host galaxy via surface brightness decomposition yields galaxy-only luminosities, thus allowing measurements of the distance moduli free of contamination from the AGNs. For 14 AGN hosts, these are the first reported distances independent of redshift, and hence independent of peculiar velocities. For the remaining galaxies, we show good agreement between our distances and those previously reported from surface brightness fluctuations and Cepheids. We also determine the total galaxy mass enclosed within the estimated H I radius, which when compared to the baryonic content allows for constraints on the dark matter masses. We find a typical mass fraction of MDM/MDYN = 62%, and find significant correlations between MBH-MDYN and MBH-MDM. Finally, we scale our galaxy radii based on estimated relationships between visible and halo radii and assume a flat rotation curve out to the halo radius to approximate MHALO. Over the range of MBH and MHALO in this sample, we find good agreement with observationally constrained relationships between MBH and MHALO and with hydrodynamical simulations.

Keywords: agn host galaxies; galaxy distances; seyfert galaxies; galaxy masses
PEARLS: JWST Counterparts of Microjansky Radio Sources in the Time Domain Field

The Time Domain Field (TDF) near the North Ecliptic Pole in JWST's continuous-viewing zone will become a premier "blank field" for extragalactic science. JWST/NIRCam data in a 16 arcmin2 portion of the TDF identify 4.4 μm counterparts for 62 of 63 3 GHz sources with S(3 GHz) > 5 μJy. The one unidentified radio source may be a lobe of a nearby Seyfert galaxy, or it may be an infrared-faint radio source. The bulk properties of the radio-host galaxies are consistent with those found by previous work: redshifts range from 0.14-4.4 with a median redshift of 1.33. The radio emission arises primarily from star formation in ~2/3 of the sample and from an active galactic nucleus (AGN) in ~1/3, but just over half the sample shows evidence for an AGN either in the spectral energy distribution or by radio excess. All but three counterparts are brighter than magnitude 23 AB at 4.4 μm, and the exquisite resolution of JWST identifies correct counterparts for sources for which observations with lower angular resolution would misidentify a nearby bright source as the counterpart when the correct one is faint and red. Up to 11% of counterparts might have been unidentified or misidentified absent NIRCam observations.

Keywords: agn host galaxies; extragalactic radio sources; high-redshift galaxies; radio galaxies
The Interstellar Medium toward the Galactic Center Source 2MASS J17470898-2829561

We describe and discuss remarkable infrared spectra, covering key portions of the 2-5 μm wavelength interval, of the probable OH/IR supergiant 2MASS J17470898-2829561 (2M1747), located in direction of the Sgr B molecular cloud complex within the Central Molecular Zone (CMZ) of the Galaxy. This star was originally singled out for examination based on its suitability for spectroscopy of lines of ${{\rm{H}}}_{3}^{+}$ in the CMZ. Analysis of the spectra shows that 2M1747 is deeply embedded within Sgr B1, with AV ≳ 100 mag, making it the only star within Sgr B for which infrared spectra have been obtained at present, and thereby a unique infrared probe of the dense interstellar medium within the CMZ. Despite the high extinction, spectra of 2M1747 reveal a veiled photosphere in the K band and circumstellar gas in the M band, giving clues as to its nature. Its 3.5-4.0 μm spectrum contains the strongest absorption lines of ${{\rm{H}}}_{3}^{+}$ observed toward any object to date. The 4.5-4.8 μm spectrum has impressively deep and wide absorption lines of interstellar CO, most of which arise in dense gas within Sgr B1. The 3-5 μm spectrum also contains several solid-state absorption features, which are characteristic of both dense and diffuse clouds, and which raise questions about the identifications of some of these features. We discuss the nature of the star, the extinction to it, the extinction law for dust in the CMZ, and the identifications of the various solid-state features and where they are produced along this complex line of sight.

Keywords: interstellar dust extinction; interstellar clouds; infrared astronomy; interstellar line absorption; interstellar molecules; dense interstellar clouds; diffuse interstellar clouds; galactic center; high resolution spectroscopy; oh/ir stars
K2, Spitzer, and TESS Transits of Four Sub-Neptune Exoplanets

We present new Spitzer transit observations of four K2 transiting sub-Neptunes: K2-36 c, K2-79b, K2-167b, and K2-212b. We derive updated orbital ephemerides and radii for these planets based on a joint analysis of the Spitzer, TESS, and K2 photometry. We use the EVEREST pipeline to provide improved K2 photometry, by detrending instrumental noise and K2's pointing jitter. We used a pixel-level decorrelation method on the Spitzer observations to reduce instrumental systematic effects. We modeled the effect of possible blended eclipsing binaries, seeking to validate these planets via the achromaticity of the transits (K2 versus Spitzer). However, we find that Spitzer's signal-to-noise ratio for these small planets is insufficient to validate them via achromaticity. Nevertheless, by jointly fitting radii between K2 and Spitzer observations, we were able to independently confirm the K2 radius measurements. Due to the long time baseline between the K2 and Spitzer observations, we were also able to increase the precision of the orbital periods compared to K2 observations alone. The improvement is a factor of 3 for K2-36 c, and more than an order of magnitude for the remaining planets. Considering possible JWST observations in 1/2023, previous 1σ uncertainties in transit times for these planets range from 74-434 minutes, but we have reduced them to the range of 8-23 minutes.

Keywords: exoplanet astronomy; photometry
3D Radiative MHD Simulations of Starspots

There are no direct spatially resolved observations of spots on stars other than the Sun, and starspot properties are inferred indirectly through lightcurves and spectropolarimetric data. We present the first self-consistent 3D radiative MHD computations of starspots on G2V, K0V, and M0V stars, which will help us to better understand observations of activity, variability, and magnetic fields in late-type main-sequence stars. We used the MURaM code, which has been extensively used to compute "realistic" sunspots, for our simulations. We aim to study how fundamental starspot properties such as intensity contrast, temperature, and magnetic field strength vary with spectral type. We first simulated in 2D multiple spots of each spectral type to find out appropriate initial conditions for our 3D runs. We find that with increasing stellar effective temperature, there is an increase in the temperature difference between the umbra of the spot and its surrounding photosphere, from 350 K on the M0V star to 1400 K on the G2V star. This trend in our simulated starspots is consistent with observations. The magnetic field strengths of all the starspot umbrae are in the 3-4.5 kG range. The G2V and K0V umbrae have comparable magnetic field strengths around 3.5 kG, while the M0V umbra has a relatively higher field strength around 4 kG. We discuss the physical reasons behind both these trends. All of the three starspots develop penumbral filament-like structures with Evershed flows. The average Evershed flow speed drops from 1.32 km s-1 in the G2V penumbra to 0.6 km s-1 in the M0V penumbra.

Keywords: starspots; radiative magnetohydrodynamics; stellar activity; sunspots; stellar magnetic fields
Interaction of a Relativistic Magnetized Collisionless Shock with a Dense Clump

The interactions between a relativistic magnetized collisionless shock and dense clumps have been expected to play a crucial role in magnetic field amplification and cosmic-ray acceleration. We investigate this process using two-dimensional Particle-In-Cell (PIC) simulations, for the first time, where the clump size is much larger than the gyroradius of the downstream particles. We also perform relativistic magnetohydrodynamic (MHD) simulations for the same condition, to see the kinetic effects. We find that particles escape from the shocked clump along magnetic field lines in the PIC simulations, so that the vorticity is lower than that in the MHD simulations. Moreover, in both the PIC and MHD simulations, the shocked clump quickly decelerates because of relativistic effects. Owing to the escape and the deceleration, the shocked clump cannot amplify the downstream magnetic field in relativistic collisionless shocks. This large-scale PIC simulation opens a new window to understanding large-scale behaviors in collisionless plasma systems.

Keywords: high energy astrophysics; magnetohydrodynamics; shocks; plasma physics; laboratory astrophysics
Radio-optical Reference Catalog, Version 1

The fundamental celestial reference frame (CRF) is based on two catalogs of astrometric positions: the third realization of the International Celestial Reference Frame (ICRF3), and the much larger Gaia CRF, built from the third data release (DR3). The objects in common between these two catalogs are mostly distant AGNs and quasars that are both sufficiently optically bright for Gaia and radio loud for the VLBI. This limited collection of reference objects is crucially important for the mutual alignment of the two CRFs and the maintenance of all of the other frames and coordinate systems branching from the ICRF. In this paper, we show that the three components of ICRF3 (S/X, K, and X/Ka band catalogs) have significantly different sky-correlated vector fields of position offsets with respect to Gaia DR3. When iteratively expanded in the vector spherical harmonics up to degree 4 on a carefully vetted set of common sources, each of these components includes several statistically significant terms. The median sky-correlated offsets from the Gaia positions are found to be 56 μas for the S/X, 100 μas for the K, and 324 μas for the X/Ka catalogs. The weighted mean vector field is subtracted from the Gaia reference positions, while the deviations from that field are added to each of the ICRF3 components. The corrected positions from each of the four input catalogs are combined into a single weighted mean catalog, which we propose to be the current most accurate realization of an inertial radio-optical CRF.

Keywords: astrometry; astronomical coordinate systems; very long baseline interferometry; radio loud quasars; gaia
Azimuthal Size Scales of Solar Wind Periodic Density Structures

Periodic density structures (PDSs) are quasiperiodic variations of solar wind density ranging from a few minutes to a few hours. PDSs advect with the solar wind and have radial length scales (L x ) of tens to several thousand megameters, thus belonging to the class of "mesoscale structures." Current interplanetary multispacecraft observations are not at spatial separations capable of directly measuring the 3D size scale of PDSs or other mesoscale structures. Instead, previous investigations estimated characteristic spatial scales in solar wind parameters using cross-correlation and/or coherence analysis applied to multispacecraft observations. For the solar wind density and interplanetary magnetic field (IMF) intensity, the reported size scales perpendicular to the Sun–Earth line (L y ) ranged between ≈30 and ≈200 Earth Radii (R E). Here, we implemented a similar approach for the same parameters, but focused on high-density, slow-solar-wind intervals with PDSs observed by the Wind and ARTEMIS-P1 spacecraft. Additionally, this is the first statistical study of the IMF intensity periodicities in relation to PDSs. We identified intervals in which the two spacecraft observed the same periodicity, obtaining two PDS groups based on their radial length scale: L x1 ≈ 86R E and L x2 ≈ 35R E. Then, we classified the events based on the periodic variations' coherence level. Reproducing the results with simulations of the PDSs' transit, we inferred the L y order of magnitudes for the two PDS groups: L y1 ≈ 340R E and L y2 ≈ 187R E. Knowing the PDSs' size scales is fundamental for constraining models aimed at reproducing these structures and is critical for better understanding the PDS–magnetosphere coupling.

Keywords: interplanetary physics; slow solar wind; solar coronal transients; interplanetary turbulence; planetary magnetospheres
WALLABY Pre-pilot Survey: The Effects of Tidal Interaction on Radial Distribution of Color in Galaxies of the Eridanus Supergroup

We study the tidal interaction of galaxies in the Eridanus supergroup, using H I data from the pre-pilot survey of the Widefield ASKAP L-band Legacy All-sky Blind surveY. We obtain optical photometric measurements and quantify the strength of tidal perturbation using a tidal parameter S sum. For low-mass galaxies of M * ≲ 109 M ⊙, we find a dependence of decreasing H I to optical disk size ratio with increasing S sum, but no dependence of H I spectral line asymmetry with S sum. This is consistent with the behavior expected under tidal stripping. We confirm that the color profile shape and color gradient depend on the stellar mass, but there is an additional correlation of low-mass galaxies having their color gradients within 2R 50 increasing with higher S sum. For these low-mass galaxies, the dependence of color gradients on S sum is driven by the color becoming progressively redder in the inner disk when tidal perturbations are stronger. For high-mass galaxies, there is no dependence of color gradients on S sum, and we find a marginal reddening throughout the disks with increasing S sum. Our result highlights tidal interaction as an important environmental effect in producing the faint end of the star formation suppressed sequence in galaxy groups.

Keywords: galaxies; interstellar atomic gas; galaxy evolution; galaxy environments