Sazuna/UAT_keywords huggingface dataset:
C<SUP>3</SUP> Cluster Clustering Cosmology I. New Constraints on the Cosmic Growth Rate at z   0.3 from Redshift-space Clustering Anisotropies. Redshift-space distortions in the clustering of galaxy clusters provide a novel probe to test the theory of gravity on cosmological scales. The aim of this work is to derive new constraints on the linear growth rate of cosmic structures from the redshift-space two-point correlation function of galaxy clusters. We construct a large spectroscopic catalog of optically selected clusters from the Sloan Digital Sky Survey. The selected sample consists of 43,743 clusters in the redshift range 0.1 &lt; z &lt; 0.42, with masses estimated from weak-lensing calibrated scaling relations. We measure the transverse and radial wedges of the two-point correlation function of the selected clusters. Modeling the redshift-space clustering anisotropies, we provide the first constraints on the linear growth rate from cluster clustering. The cluster masses are used to set a prior on the linear bias of the sample. This represents the main advantage in using galaxy clusters as cosmic probes, instead of galaxies. Assuming a standard cosmological model consistent with the latest cosmic microwave background constraints, we do not find any evidence of deviations from general relativity. Specifically, we get the value of the growth rate times the matter power spectrum normalization parameter fσ8 = 0.44 ± 0.05, at an effective redshift of z = 0.275.

Keywords: Galaxy clusters, Observational cosmology, Redshift surveys, Cosmological parameters
Influence of Large-scale Field Structures on the Scaling Anisotropy in 3D MHD Turbulence. Magnetohydrodynamic (MHD) turbulence is revealed to have scaling anisotropy based on structure function calculations. Recent studies on solar wind turbulence found that the scaling anisotropy disappears when removing large-scale field structures. This finding raises questions as to whether numerical MHD turbulences have large-scale field structures. How do these structures affect the scaling anisotropy therein? Here we investigate these questions with a driven compressible three-dimensional MHD turbulence. We introduce a new method to check how the random stationarity condition is satisfied. We find for the first time in the numerical MHD turbulence that the large-scale field structures destroy the random stationarity of the local fields and make samplings nonparallel to the instantaneous fields be calculated as apparent parallel samplings. This mixture makes statistical calculations show anisotropic scaling of the turbulence. When we select only the random stationary data intervals, the statistical results show an isotropic nature. We also find that among the large-scale field structures, one-third are tangential discontinuities (TDs), one-third are rotational discontinuities (RDs), and the rest are EDs (either TD or RD). These results show that the large-scale structures in the numerical MHD turbulence have important influence on the structure function analysis.

Keywords: Interplanetary turbulence, Solar wind, Magnetohydrodynamical simulations
Minute-timescale Variability in the X-ray Emission of the Highest Redshift Blazar. We report on two Chandra observations of the quasar PSO J0309+27, the most distant blazar observed so far (z = 6.1), performed eight months apart, in 2020 March and November. Previous Swift-XRT observations showed that this object is one of the brightest X-ray sources beyond redshift 6.0 ever observed so far. This new dataset confirmed the high flux level and unveiled a spectral change that occurred on a very short timescale (250 s rest frame), caused by a significant softening of the emission spectrum. This kind of spectral variability, on such a short interval, has never been reported in the X-ray emission of a flat-spectrum radio quasar. A possible explanation for this is given by the emission produced by the inverse Compton scatter of the quasar UV photons by the cold electrons present in a fast shell moving along the jet. Although this bulk Comptonization emission should be an unavoidable consequence of the standard leptonic jet model, this would be the first time that it has been observed. * ...

Keywords: Jets, Quasars, Blazars, Flat-spectrum radio quasars, Radio loud quasars
An Arecibo Search for Fast Radio Transients from M87. The possible origin of millisecond bursts from the giant elliptical galaxy M87 has been scrutinized since the earliest searches for extragalactic fast radio transients undertaken in the late 1970s. Motivated by rapid technological advancements in recent years, we conducted ≃10 hr of L-band (1.15-1.75 GHz) observations of the core of M87 with the Arecibo radio telescope in 2019. Adopting a matched filtering approach, we searched our data for single pulses using trial dispersion measures up to 5500 pc cm-3 and burst durations between 0.3-123 ms. We find no evidence of astrophysical bursts in our data above a 7σ detection threshold. Our observations thus constrain the burst rate from M87 to ≲ 0.1 bursts hr-1 above 1.4 Jy ms, the most stringent upper limit obtained to date. Our nondetection of radio bursts is consistent with expectations of giant pulse emission from a Crab-like young neutron star population in M87. However, the dense, strongly magnetized interstellar medium surrounding the central ~109 M⊙ supermassive black hole of M87 may potentially harbor magnetars that can emit detectable radio bursts during their flaring states.

Keywords: Neutron stars, Magnetars, Radio transient sources, Radio pulsars
Short-term Spectroscopic Variability of the Early Post-AGB Stage Star IRAS 22272+5435. High-resolution spectra gathered during an extensive monitoring of IRAS 22272+5435 are inspected to search for spectroscopic variability in the time span of less than 2 weeks. Significant variation are found both in the intensity and position of CN(1, 0) red system lines near the light maximum, when the star is the hottest. The intensity of variable CN lines correlates with their Doppler redshift-an increase in the radial velocity leads to a decrease of its equivalent width. The inward flow of increasing velocity from ≃14.4-21.6 km s-1 was confirmed in the atmosphere, propagating ~25 R⊙ toward the mass center of the star in 11 days. The variability of CN(1, 0) lines are accompanied by changes in the red wings of strong low-excitation lines. The observed short-term variations are attributed to large-scale convective flows and shock waves in the extended atmosphere of a cool pulsating post-AGB star.

Keywords: High resolution spectroscopy, Post-asymptotic giant branch stars, Shocks, Circumstellar matter, Stellar oscillations, Stellar atmospheres
The Prominence Driven Forced Reconnection in the Solar Corona and Associated Plasma Dynamics. Using the multitemperature observations from SDO/AIA on 2019 December 30, we provide a signature of prominence driven forced magnetic reconnection in the corona and associated plasma dynamics from 09:20 UT to 10:38 UT. A hot prominence segment erupts with a speed of ≈21 km s-1 and destabilizes the entire prominence system. Thereafter, it rises upward in the north from 09:28 UT to 09:48 UT with a speed of 24 km s-1 . The eruptive prominence stretches overlying field lines upward with the speed of 27-28 km s-1, which further undergo the forced reconnection. The coronal plasma also flows southward with a speed of 7 km s-1, and both of these inflows trigger the reconnection at ≈09:48 UT. Thereafter, the eastward and westward magnetic channels are developed and separated. The east-west reorganization of the magnetic fields starts creating bidirectional plasma outflows toward the limb with their respective speeds of 28 and 37 km s-1. Their upper ends are diffused in the overlying corona, transporting another set of upflows with the speeds of ≈22 km and 19 km s-1. The multitemperature plasma (log Te = 6.0-7.2 K) evolves and elongates to a length of ≈105 km on the reorganized fields. The hot plasma and remaining prominence threads move from the reconnection region toward another segment of a prominence in the eastward direction. The prominence-prominence/loop interaction and associated reconnection generate jet-like eruptions with a speed of 178-183 km s-1. After the formation of the jet, the overlying magnetic channel disappears in the corona.

Keywords: Solar coronal loops, Magnetic fields, Solar corona, Solar magnetic reconnection
A Spectroscopic Analysis of the California-Kepler Survey Sample. II. Correlations of Stellar Metallicities with Planetary Architectures. We present independent and self-consistent metallicities for a sample of 807 planet-hosting stars from the California-Kepler Survey from an LTE spectroscopic analysis using a selected sample of Fe I and Fe II lines. Correlations between host-star metallicities, planet radii, and planetary architecture (orbital periods-warm or hot-and multiplicity-single or multiple) were investigated using nonparametric statistical tests. In addition to confirming previous results from the literature, e.g., that overall host-star metallicity distributions differ between hot and warm planetary systems of all types, we report on a new finding: when comparing the median metallicities of hot versus warm systems, the difference for multiple super-Earths is considerably larger when compared to that difference in single super-Earths. The metallicity cumulative distribution functions of hot single super-Earths versus warm single super-Earths indicate different parent stellar populations, while for sub-Neptunes this is not the case. The transition radius between sub-Neptunes and sub-Saturns was examined by comparing the APOGEE metallicity distribution for the Milky Way thin disk in the solar neighborhood with metallicity distributions of host stars segregated based upon the largest known planet in their system. These comparisons reveal increasingly different metallicity distributions as the radius of the largest planet in the systems increases, with the parent stellar metallicities becoming significantly different for Rp &gt; 2.7 R⊕. The behavior of the p-values as a function of planet radius undergoes a large slope change at Rp = 4.4 ± 0.5 R⊕, indicating the radius boundary between small and large planets.

Keywords: High resolution spectroscopy, Fundamental parameters of stars, Stellar abundances, Planetary system formation, Stellar atmospheres
An Improved Near-infrared Spectrum of the Archetype Y Dwarf WISEP J182831.08+265037.8. We present a Hubble Space Telescope/Wide-Field Camera 3 near-infrared spectrum of the archetype Y dwarf WISEP 182831.08+265037.8. The spectrum covers the 0.9-1.7 μm wavelength range at a resolving power of λ/Δλ ≈ 180 and is a significant improvement over the previously published spectrum because it covers a broader wavelength range and is uncontaminated by light from a background star. The spectrum is unique for a cool brown dwarf in that the flux peaks in the Y, J, and H bands are of near equal intensity in units of fλ. We fail to detect any absorption bands of NH3 in the spectrum, in contrast to the predictions of chemical equilibrium models, but tentatively identify CH4 as the carrier of an unknown absorption feature centered at 1.015 μm. Using previously published ground- and spaced-based photometry, and using a Rayleigh-Jeans tail to account for flux emerging longward of 4.5 μm, we compute a bolometric luminosity of \mathrm{log}({L}_{\mathrm{bol}}/{{ \mathcal L }}_{\odot }^{N})=-6.50\pm 0.02$ , which is significantly lower than previously published results. Finally, we compare the spectrum and photometry to two sets of atmospheric models and find that the best overall match to the observed properties of WISE 1828+2650 is a ~1 Gyr old binary composed of two Teff ~ 325 K, ~5 MJup brown dwarfs with subsolar [C/O] ratios.

Keywords: Brown dwarfs, Y dwarfs, Spectroscopy, Near infrared astronomy
Estimating Magnetic Filling Factors from Simultaneous Spectroscopy and Photometry: Disentangling Spots, Plage, and Network. State-of-the-art radial velocity (RV) exoplanet searches are limited by the effects of stellar magnetic activity. Magnetically active spots, plage, and network regions each have different impacts on the observed spectral lines and therefore on the apparent stellar RV. Differentiating the relative coverage, or filling factors, of these active regions is thus necessary to differentiate between activity-driven RV signatures and Doppler shifts due to planetary orbits. In this work, we develop a technique to estimate feature-specific magnetic filling factors on stellar targets using only spectroscopic and photometric observations. We demonstrate linear and neural network implementations of our technique using observations from the solar telescope at HARPS-N, the HK Project at the Mt. Wilson Observatory, and the Total Irradiance Monitor onboard SORCE. We then compare the results of each technique to direct observations by the Solar Dynamics Observatory. Both implementations yield filling factor estimates that are highly correlated with the observed values. Modeling the solar RVs using these filling factors reproduces the expected contributions of the suppression of convective blueshift and rotational imbalance due to brightness inhomogeneities. Both implementations of this technique reduce the overall activity-driven rms RVs from 1.64 to 1.02 m s-1, corresponding to a 1.28 m s-1 reduction in the rms variation. The technique provides an additional 0.41 m s-1 reduction in the rms variation compared to traditional activity indicators.

Keywords: Exoplanet detection methods, Exoplanets, Solar active regions, Solar activity, Radial velocity
Chandra X-Ray Observations of V830 Tau: A T Tauri Star Hosting an Evanescent Planet. The radial velocity study by Donati et al. (2016) reported the detection of a close-in giant planet in a 4.93 day orbit around the ~2 Myr old weak-lined T Tauri star V830 Tau. Because of the stringent timescale constraints that a very young host star like V830 Tau would place on hot-Jupiter formation models and inward-migration mechanisms, independent confirmation of the planet's existence is needed but so far has not been obtained. We present new Chandra X-ray observations of V830 Tau. The Chandra observations in combination with previous XMM-Newton observations reveal strong, variable X-ray emission with an X-ray luminosity spanning the range log Lx = 30.10-30.87 erg s-1. Chandra High Energy Transmission Grating spectra show emission lines formed over a range of plasma temperatures from ~4 MK (Ne IX) to ~16 MK (S XV). At the separation of the reported planet (0.057 au) the X-ray flux is ~106-107 times greater than the Sun's X-ray flux at Jupiter. We provide estimates of the X-ray ionization and atmospheric heating rates at the planet's separation and identify areas of uncertainty that will need to be addressed in any future atmospheric models.

Keywords: T Tauri stars, X-ray stars
Two Sequences in the Age-Metallicity Relation as Seen from [C/N] Abundances in APOGEE. The age-metallicity relation (AMR) is fundamental to study the formation and evolution of the disk. Observations have shown that this relation has a large scatter, which cannot be explained by observational errors only. That scatter is hence attributed to the effects of radial migration in which stars tracing different chemical evolution histories in the disk get mixed. However, the recent study of Nissen et al., using high-precision observational data of solar-type stars, found two relatively tight AMRs. One sequence of older and metal-richer stars probably traces the chemical enrichment history of the inner disk while the other sequence of younger and metal-poorer stars traces the chemical enrichment history of the outer disk. If uncertainties in age measurements increase, these sequences mix, explaining the scatter of the one relation observed in other studies. This work follows up on these results by analyzing an independent sample of red clump giants observed by APOGEE. Because ages for red giants are significantly more uncertain, the [C/N] ratios are considered as a proxy for age. This larger data set is used to investigate these relations at different Galactic radii, finding that these distinct sequences exist only in the solar neighborhood. The APOGEE data set is further used to explore different abundance and kinematical planes to shed light on the nature of these populations.

Keywords: Milky Way disk, Chemical abundances
Multiphase Powerful Outflows Detected in High-z Quasars. We present results from a comprehensive study of ultrafast outflows (UFOs) detected in a sample of 14 quasars, 12 of which are gravitationally lensed, in a redshift range of 1.41-3.91, near the peak of the active galactic nucleus (AGN) and star formation activity. New XMM-Newton observations are presented for six of them, which were selected to be lensed and contain a narrow absorption line (NAL) in their UV spectra. Another lensed quasar was added to the sample, albeit already studied because it was not searched for UFOs. The remaining seven quasars of our sample are known to contain UFOs. The main goals of our study are to infer the outflow properties of high-z quasars, constrain their outflow induced feedback, study the relationship between the outflow properties and the properties of the ionizing source, and compare these results to those of nearby AGN. Our study adds six new detections (&gt; 99% confidence) of UFOs at z &gt; 1.4, almost doubling the current number of cases. Based on our survey of six quasars selected to contain a NAL and observed with XMM-Newton, the coexistence of intrinsic UV NALs and UFOs is found to be significant in &gt;83% of these quasars suggesting a link between multiphase AGN feedback properties of the meso- and microscale. The kinematic luminosities of the UFOs of our high-z sample are large compared to their bolometric luminosities (median of LK/LBol ≳ 50%). This suggests they provide efficient feedback to influence the evolution of their host galaxies and that magnetic driving may be a significant contributor to their acceleration.

Keywords: Galaxy formation, Quasars, X-ray quasars, Gravitational lensing, Galaxy evolution
Flare-induced Sunquake Signatures in the Ultraviolet as Observed by the Atmospheric Imaging Assembly. Sunquakes (SQs) have been routinely observed in the solar photosphere, but it is only recently that signatures of these events have been detected in the chromosphere. We investigate whether signatures of SQs are common in ultraviolet (UV) continua that sample the solar plasma several hundred km above where SQs are typically detected. We analyze observations from the Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA) 1600 and 1700 Å passbands, for SQ signatures induced by the flares of Solar Cycle 24. We base our analysis on the 62 SQs detected in the recent statistical study presented by Sharykin &amp; Kosovichev. We find that 9 out of 62 SQ candidates produced a response that is clearly detected in running-difference images from the AIA 1600 and 1700 Å channels. A binary frequency filter with a width of 2 mHz, centered on 6 mHz, was applied to the data. The first signature of each SQ was detected at distances between 5.2 and 25.7 Mm from the associated flare ribbon. Time-distance and regression analysis allowed us to calculate the apparent transverse velocities of the SQs in the UV data sets and found maximum velocities as high as 41 km s-1, 87 Mm away from the SQ source. Our analysis shows that flare-induced SQ signatures can be detected in the SDO/AIA 1600 and 1700 Å passbands, hinting at their presence in the lower chromosphere. There was no apparent correlation between GOES flare classification and the appearance of the SQ at these heights.

Keywords: Helioseismology, Solar atmosphere, Solar physics
Simulating Relic Gravitational Waves from Inflationary Magnetogenesis. We present three-dimensional direct numerical simulations of the production of magnetic fields and gravitational waves (GWs) in the early universe during a low energy scale matter-dominated post-inflationary reheating era, and during the early subsequent radiative era, which is strongly turbulent. The parameters of the model are determined such that it avoids a number of known physical problems and produces magnetic energy densities between 0.03% and 0.5% of the critical energy density at the end of reheating. During the subsequent development of a turbulent magnetohydrodynamic cascade, magnetic fields and GWs develop a spectrum that extends to higher frequencies in the millihertz (nanohertz) range for models with reheating temperatures of around 100 GeV (150 MeV) at the beginning of the radiation-dominated era. However, even though the turbulent cascade is fully developed, the GW spectrum shows a sharp drop for frequencies above the peak value. This suggests that the turbulence is less efficient in driving GWs than previously thought. The peaks of the resulting GW spectra may well be in the range accessible to space interferometers, pulsar timing arrays, and other facilities.

Keywords: Magnetohydrodynamics, Astrophysical fluid dynamics
On the Crystallinity of Silicate Dust in Evolving Protoplanetary Disks due to Magnetically Driven Disk Winds. We present a novel mechanism for the outward transport of crystalline dust particles: the outward radial drift of pebbles. A dust-ring structure is frequently observed in protoplanetary disks. One of the plausible mechanisms for the formation of dust rings is the accumulation of pebbles around the pressure maximum, which is formed by the mass loss due to magnetically driven disk winds. Due to magnetically driven disk winds, dust particles in evolving protoplanetary disks can migrate outwardly from the crystallization front to the pressure maximum by radial drift. We found that the outward radial drift process can transport crystalline dust particles efficiently when the radial drift timescale is shorter than the advection timescale. Our model predicts that the crystallinity of silicate dust particles could be as high as 100% inside the dust-ring position.

Keywords: Silicate grains, Planetary system formation, Protoplanetary disks, Circumstellar disks, Planet formation
On the Spin Dynamics of Elongated Minor Bodies with Applications to a Possible Solar System Analogue Composition for 'Oumuamua. The first interstellar object, 1I/2017 U1 ('Oumuamua), exhibited several unique properties, including an extreme aspect ratio, a lack of typical cometary volatiles, and a deviation from a Keplerian trajectory. Several authors have hypothesized that the non-gravitational acceleration was caused by either cometary outgassing or radiation pressure. Here, we investigate the spin dynamics of 'Oumuamua under the action of high-surface-area fractional activity and radiation pressure. We demonstrate that a series of transient jets that migrate across the illuminated surface will not produce a secular increase in the spin rate. We produce 3D tumbling simulations that approximate the dynamics of a surface-covering jet and show that the resulting synthetic light curve and periodogram are reasonably consistent with the observations. Moreover, we demonstrate that radiation pressure also produces a steady spin state. While carbon monoxide (CO) has been dismissed as a possible accelerant because of its non-detection in emission by Spitzer, we show that outgassing from a surface characterized by a modest covering fraction of CO ice can satisfy the non-ballistic dynamics for a plausible range of assumed bulk densities and surface albedos. Spitzer upper limits on CO emission are, however, inconsistent with the CO production necessary to provide the acceleration. Nonetheless, an ad hoc but physically plausible explanation is that the activity level varied greatly during the time that the trajectory was monitored. We reproduce the astrometric analysis presented in Micheli et al., and verify that the non-gravitational acceleration was consistent with stochastic changes in outgassing.

Keywords: Interstellar objects