adsabs/SciX_UAT_keywords huggingface dataset:
Peculiar Orbital Characteristics of Earth Quasi-Satellite 469219 Kamo'oalewa: Implications for the Yarkovsky Detection and Orbital Uncertainty Propagation

469219 Kamo'oalewa is selected as one of the primary targets of Tianwen-2 mission, which is currently believed to be the most stable quasi-satellite of Earth. Here we derive a weak detection of the Yarkovsky effect for Kamo'oalewa, giving A 2 = (-1.075 ± 0.447) × 10-13 au day-2, with the available ground-based optical observations from Minor Planet Center and a relatively conservative weighting scheme. Due to the quasi-satellite resonance with Earth, we show that the detection of the Yarkovsky effect by orbital fitting with astrometric observations becomes difficult, as its orbital drift shows a slow oscillatory growth resulting from the Yarkovsky effect. In addition, we extensively explore the characteristics of orbital uncertainty propagation and find that the positional uncertainty mainly arises from the geocentric radial direction in 2010-2020 and then concentrates in the heliocentric transverse direction in 2020-2030. Furthermore, the heliocentric transverse uncertainty is clearly monthly dependent, which can arrive at a minimum around January and a maximum around July as the orbit moves toward the leading and trailing edges, respectively, in 2025-2027. Finally, we investigate a long-term uncertainty propagation in the quasi-satellite regime, implying that the quasi-satellite resonance with Earth may play a crucial role in constraining the increase of uncertainty over time. Such an interesting feature further implies that the orbital precision of Kamo'oalewa is relatively stable at its quasi-satellite phase, which may also be true for other quasi-satellites of Earth.

Keywords: asteroids; asteroid dynamics
Fast Radio Bursts and Their High-energy Counterparts from Magnetar Magnetospheres

The recent discovery of a Galactic fast radio burst (FRB) occurring simultaneously with an X-ray burst (XRB) from the Galactic magnetar SGR J1935+2154 implies that at least some FRBs arise from magnetar activities. We propose that FRBs are triggered by crust fracturing of magnetars, with the burst event rate depending on the magnetic field strength in the crust. Since the crust-fracturing rate is relatively higher in polar regions, FRBs are more likely to be triggered near the directions of multipolar magnetic poles. Crust fracturing produces Alfvén waves, forming a charge-starved region in the magnetosphere and leading to nonstationary pair plasma discharges. An FRB is produced by coherent plasma radiation due to nonuniform pair production across magnetic field lines. Meanwhile, the FRB-associated XRB is produced by the rapid relaxation of the external magnetic field lines. In this picture, the sharp-peak hard X-ray component in association with FRB 200428 is from a region between adjacent trapped fireballs, and its spectrum with a high cutoff energy is attributed to resonant Compton scattering. The persistent X-ray emission is from a hot spot heated by the magnetospheric activities, and its temperature evolution is dominated by magnetar surface cooling. Within this picture, magnetars with stronger fields tend to produce brighter and more frequent repeated bursts.

Keywords: x-ray bursts; non-thermal radiation sources; radio transient sources; pulsars
In-orbit Performance of the Near-infrared Spectrograph NIRSpec on the James Webb Space Telescope

The Near-Infrared Spectrograph (NIRSpec) is one of the four focal plane instruments on the James Webb Space Telescope. In this paper, we summarize the in-orbit performance of NIRSpec, as derived from data collected during its commissioning campaign and the first few months of nominal science operations. More specifically, we discuss the performance of some critical hardware components such as the two NIRSpec Hawaii-2RG detectors, wheel mechanisms, and the microshutter array. We also summarize the accuracy of the two target acquisition procedures used to accurately place science targets into the slit apertures, discuss the current status of the spectrophotometric and wavelength calibration of NIRSpec spectra, and provide the "as measured" sensitivity in all NIRSpec science modes. Finally, we point out a few important considerations for the preparation of NIRSpec science programs.

Keywords: space vehicle instruments; spectrometers; spectroscopy; space telescopes
Properties and Astrophysical Implications of the 150 M⊙ Binary Black Hole Merger GW190521

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, ${85}_{-14}^{+21}$ M⊙ and ${66}_{-18}^{+17}$ M⊙, compared to previously reported events, and shows mild evidence for spin-induced orbital precession. The primary falls in the mass gap predicted by (pulsational) pair-instability supernova theory, in the approximate range 65-120 M⊙. The probability that at least one of the black holes in GW190521 is in that range is 99.0%. The final mass of the merger ( ${142}_{-16}^{+28}$ M⊙) classifies it as an intermediate-mass black hole. Under the assumption of a quasi-circular BBH coalescence, we detail the physical properties of GW190521's source binary and its post-merger remnant, including component masses and spin vectors. Three different waveform models, as well as direct comparison to numerical solutions of general relativity, yield consistent estimates of these properties. Tests of strong-field general relativity targeting the merger-ringdown stages of the coalescence indicate consistency of the observed signal with theoretical predictions. We estimate the merger rate of similar systems to be ${0.13}_{-0.11}^{+0.30}\,{{\rm{Gpc}}}^{-3}\,{{\rm{yr}}}^{-1}$ . We discuss the astrophysical implications of GW190521 for stellar collapse and for the possible formation of black holes in the pair-instability mass gap through various channels: via (multiple) stellar coalescences, or via hierarchical mergers of lower-mass black holes in star clusters or in active galactic nuclei. We find it to be unlikely that GW190521 is a strongly lensed signal of a lower-mass black hole binary merger. We also discuss more exotic possible sources for GW190521, including a highly eccentric black hole binary, or a primordial black hole binary.

Keywords: astrophysical black holes; high energy astrophysics; gravitational collapse; gravitation; gravitational wave astronomy; gravitational wave sources; ligo; stellar populations; intermediate-mass black holes
First Results for Solar Soft X-Ray Irradiance Measurements from the Third-generation Miniature X-Ray Solar Spectrometer

Three generations of the Miniature X-ray Solar Spectrometer (MinXSS) have flown on small satellites with the goal "to explore the energy distribution of soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during solar flares, and to model the impact on Earth's ionosphere and thermosphere." The primary science instrument is the Amptek X123 X-ray spectrometer that has improved with each generation of the MinXSS experiment. This third-generation MinXSS-3 has a higher energy resolution and larger effective area than its predecessors and is also known as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). It was launched on the INSPIRESat-1 satellite on 2022 February 14, and INSPIRESat-1 has successfully completed its 6 month prime mission. The INSPIRESat-1 is in a dawn-dusk, Sun-synchronous orbit and therefore has had 24 hr coverage of the Sun during most of its mission so far. The rise of Solar Cycle 25 has been observed by DAXSS. This paper introduces the INSPIRESat-1 DAXSS solar SXR observations, and we focus the science results here on a solar occultation experiment and multiple flares on 2022 April 24. One key flare result is that the reduction of elemental abundances appears greatest during the flare impulsive phase, thus highlighting the important role of chromospheric evaporation during flares to inject warmer plasma into the coronal loops. Furthermore, these results are suggestive that the amount of chromospheric evaporation is related to flare temperature and intensity.

Keywords: solar corona; solar flare spectra; solar x-ray emission; occultation; x-ray detectors
Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies

In modified Newtonian dynamics (MOND)-based theories, the strong equivalence principle is generically broken in an idiosyncratic manner, manifested in the action of an "external field effect" (EFE). The internal dynamics in a self-gravitating system is affected even by a constant external field. In disk galaxies, the EFE can induce warps and modify the rotational speeds. Due to the nonlinearity of MOND, it is difficult to derive analytic expressions of this important effect in a disk. Here we study numerically the EFE in two nonrelativistic Lagrangian theories of MOND: the "Aquadratic-Lagrangian" theory (AQUAL) and "Quasilinear MOND" (QUMOND). For AQUAL, we consider only the axisymmetric field configurations with the external field along the disk axis, or a spherical galaxy with test-particle orbits inclined to the external field. For the more manageable QUMOND, we also calculate the three-dimensional field configurations, with the external field inclined to the disk axis. We investigate in particular to what degree an external field modifies the quasi-flat part of rotation curves. While our QUMOND results agree well with published numerical results in QUMOND, we find that AQUAL predicts weaker EFE than published AQUAL results. However, AQUAL still predicts stronger EFE than QUMOND, which demonstrates current theoretical uncertainties. We also illustrate how the MOND prediction on the rising part of the rotation curve, in the inner parts, depends largely on disk thickness but only weakly on a plausible external field for a fixed galaxy model. Finally, we summarize our results for the outer parts as an improved, approximate analytic expression.

Keywords: modified newtonian dynamics; non-standard theories of gravity; computational methods; gravitation
Sequential Small Coronal Mass Ejections Observed In Situ and in White-Light Images by Parker Solar Probe

We reconstruct the morphology and kinematics of a series of small transients that erupted from the Sun on 2021 April 24 using observations primarily from Parker Solar Probe (PSP). These sequential small coronal mass ejections (CMEs) may be the product of a continuous reconnection at a current sheet, which is a macroscopic example of the more microscopic reconnection activity that has been proposed to accelerate the solar wind more generally. These particular CMEs are of interest because they are the first CMEs to hit PSP and be simultaneously imaged by it, using the Wide-field Imager for Solar Probe (WISPR) instrument. Based on imaging from WISPR and STEREO-A, we identify and model six discrete transients, and determine that it is the second of them (CME2) that first hits PSP, although PSP later more obliquely also encounters the third transient. Signatures of these encounters are seen in the PSP in situ data. Within these data, we identify six candidate magnetic flux ropes (MFRs), all but one of which are associated with the second transient. The five CME2 MFRs have orientations that are roughly consistent with PSP encountering the right-hand sides of roughly E-W oriented MFRs, which are sloping back toward the Sun.

Keywords: solar coronal mass ejections; solar wind; interplanetary magnetic fields; interplanetary physics
Faint Quasars Live in the Same Number Density Environments as Lyman Break Galaxies at z ∼ 4

Characterizing high-z quasar environments is key to understanding the coevolution of quasars and the surrounding galaxies. To restrict their global picture, we statistically examine the g-dropout galaxy overdensity distribution around 570 faint quasar candidates at z ∼ 4, based on the Hyper Suprime-Cam Subaru Strategic Program survey. We compare the overdensity significances of g-dropout galaxies around the quasars with those around g-dropout galaxies, and find no significant difference between their distributions. A total of 4 (22) out of the 570 faint quasars, ${0.7}_{-0.4}^{+0.4}$ $({3.9}_{-0.8}^{+0.8}) \% $, are found to be associated with the >4σ overdense regions within an angular separation of 1.8 (3.0) arcmin, which is the typical size of protoclusters at this epoch. This is similar to the fraction of g-dropout galaxies associated with the >4σ overdense regions. This result is consistent with our previous work in which ${1.3}_{-0.9}^{+0.9} \% $ and ${2.0}_{-1.1}^{+1.1} \% $ of luminous quasars detected in the Sloan Digital Sky Survey exist in the >4σ overdense regions within 1'8 and 3'0 separations, respectively. Therefore, we suggest that the galaxy number densities around quasars are independent of their luminosity, and most quasars do not preferentially appear in the richest protocluster regions at z ∼ 4. The lack of an apparent positive correlation between the quasars and the protoclusters implies that (i) the gas-rich major merger rate is relatively low in the protocluster regions, (ii) most high-z quasars may appear through secular processes, or (iii) some dust-obscured quasars exist in the protocluster regions.

Keywords: quasars; galaxy evolution; lyman-break galaxies; protoclusters; galaxy formation
The Metallicity Variations Along the Chromosome Maps: The Globular Cluster 47 Tucanae

The "chromosome maps" (ChMs) of globular clusters (GCs) have revealed that these ancient structures are inhomogeneous in metallicity in various ways and in different natures. Type II GCs generally display larger variations, sometimes coupled with slow neutron-capture (s) element enrichments on the ChMs redder sequences, which have been interpreted as due to multiple generations of stars. On the other hand, most GCs have inhomogeneous first populations (1P) in the form of large ranges in the ΔF275W,F814W values, pointing toward a not fully mixed pristine molecular cloud. We analyze the chemical composition of GC 47 Tucanae, which shows both inhomogeneous 1P stars and, although not formally a Type II GC, hosts a small number of stars distributed on the red side of the main stream of ChM stars. Our results suggest that 1P stars are inhomogeneous in the overall metallicity, with variations on the order of ~0.10 dex in all the chemical species. The anomalous stars distributed on a redder sequence of the ChM are further enriched in metals but have no evidence for a significant enrichment in the s elements. Our three second population stars located on the normal component of the map have metallicities similar to those of the metal-richer 1P oup, suggesting that this population formed from these stars. Although three stars is a too-small sample to draw strong conclusions, the low spread in metals of these objects might point toward formation in a fully mixed medium, possibly after a cooling flow phase. *Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO program 105.20NB, and on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Keywords: star clusters; chemical abundances; population ii stars
The Behavior of HgMn Stars in the Far UV-Paper 20: HD 14228

The analysis of three spectra of the Mn Hg Sr star HD 14228 recorded by the SWP camera on board the International Ultraviolet Explorer does not reveal variations of the far-ultraviolet flux over a nine years time interval. The analysis of the TESS lightcurve of HD 14228 confirms a very short period of 0.34 day already reported in the literature. This periodicity, attributed to rotation, could be a mode of radial pulsation too.

Keywords: chemically peculiar stars; mercury-manganese stars
Simultaneous Time-monitoring Observations of H2O and SiO Masers toward the Supergiant VX Sagittarii

We performed simultaneous monitoring observations of the 22.2 GHz H2O and 43.1/42.8/86.2/129.3 GHz SiO masers toward the red supergiant VX Sagittarii using the Korean VLBI Network single-dish telescopes. The observations were conducted about every 2 months from 2013 May to 2019 January (30 epochs in total). They included four optical maxima in the active phase of the optical pulsation cycles. The line profile of a H2O maser always comprised various velocity components with a wider velocity range and varied from highly redshifted to blueshifted velocities with respect to the stellar velocity, in contrast to those of the SiO masers. We examined the relation between peak intensities and velocities of 11 detailed components in the line profile of the H2O maser and the pulsation phases. The peak intensity of each component generally exhibited a better correlation with the pulsation phases than that of total intensity. The peak velocities of several components gradually decreased or increased with respect to the stellar velocity, implying an accelerating motion and the development of asymmetries in the H2O maser region. The characteristics of four transition SiO maser properties were compared according to the stellar pulsation phases. The intensity and velocity variation trend of the 43.1 GHz SiO maser was similar to that of the 42.8 GHz SiO maser. However, the variation trend of the 43.1 and 42.8 GHz SiO masers was different from that of the 86.2 and 129.3 GHz SiO masers. This difference stems from the different location of each maser reflecting a different excitation condition.

Keywords: circumstellar masers; interstellar masers; water masers; a supergiant stars; radio astrometry; single-dish antennas; silicon monoxide masers
A Deeper Look at DES Dwarf Galaxy Candidates: Grus I and Indus II

We present deep g- and r-band Magellan/Megacam photometry of two dwarf galaxy candidates discovered in the Dark Energy Survey (DES), Grus I and Indus II (DES J2038-4609). For the case of Grus I, we resolved the main sequence turn-off (MSTO) and ~2 mags below it. The MSTO can be seen at g0 ~ 24 with a photometric uncertainty of 0.03 mag. We show Grus I to be consistent with an old, metal-poor (~13.3 Gyr, [Fe/H] ~ -1.9) dwarf galaxy. We derive updated distance and structural parameters for Grus I using this deep, uniform, wide-field data set. We find an azimuthally-averaged halflight radius more than two times larger (~151+21-31 pc; ~ $4\buildrel{\,\prime}\over{.} {16}_{-0.74}^{+0.54}$) and an absolute V-band magnitude ~-4.1 that is ~1 magnitude brighter than previous studies. We obtain updated distance, ellipticity, and centroid parameters that are in agreement with other studies within uncertainties. Although our photometry of Indus II is ~2-3 magnitudes deeper than the DES Y1 public release, we find no coherent stellar population at its reported location. The original detection was located in an incomplete region of sky in the DES Y2Q1 data set and was flagged due to potential blue horizontal branch member stars. The best-fit isochrone parameters are physically inconsistent with both dwarf galaxies and globular clusters. We conclude that Indus II is likely a false positive, flagged due to a chance alignment of stars along the line of sight.

Keywords: dwarf galaxies; astronomy data analysis; photometry; galaxy properties; bayesian statistics
Mass Ratio of Single-line Spectroscopic Binaries with Visual Orbits Using Bayesian Inference and Suitable Priors

We present orbital elements for 22 single-line binaries, nine of them studied for the first time, determined from a joint spectroscopic and astrometric solution. The astrometry is based on interferometric measurements obtained with the HRCam Speckle camera on the SOAR 4.1 m telescope at Cerro Pachon, Chile, supplemented with historical data. The spectroscopic observations were secured using Echelle spectrographs (FEROS, FIDEOS, and HARPS) at La Silla, Chile. A comparison of our orbital elements and systemic velocities with previous studies, including Gaia radial velocities, shows the robustness of our estimations. By adopting suitable priors of the trigonometric parallax and spectral type of the primary component, and using a Bayesian inference methodology developed by our group, we were able to estimate mass ratios for these binaries. Combining the present results with a previous study of other single-line binaries from our team, we present a pseudo mass-to-luminosity relationship based on 23 systems (46 stars) in the mass range 0.6 ≤ M ⊙ ≤ 2.5. We find a reasonable correspondence with a fiducial mass-to-luminosity relationship. We conclude that our methodology does allow us to derive tentative mass ratios for these types of binaries. *Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovaçãoes (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

Keywords: binary stars; astrometric binary stars; visual binary stars; interferometric binary stars; stellar masses; stellar properties; mass ratio; spectroscopic binary stars; bayesian statistics; posterior distribution; prior distribution; stellar luminosities
A Gravitational Redshift Measurement of the White Dwarf Mass-Radius Relation

The mass-radius relation of white dwarfs is largely determined by the equation of state of degenerate electrons, which causes the stellar radius to decrease as mass increases. Here we observationally measure this relation using the gravitational redshift effect, a prediction of general relativity that depends on the ratio between stellar mass and radius. Using observations of over 3000 white dwarfs from the Sloan Digital Sky Survey and the Gaia space observatory, we derive apparent radial velocities from absorption lines, stellar radii from photometry and parallaxes, and surface gravities by fitting atmospheric models to spectra. By averaging the apparent radial velocities of white dwarfs with similar radii and, independently, surface gravities, we cancel out random Doppler shifts and measure the underlying gravitational redshift. Using these results, we empirically measure the white dwarf mass-radius relation across a wide range of stellar masses. Our results are consistent with leading theoretical models, and our methods could be used with future observations to empirically constrain white dwarf core composition and evolution.

Keywords: white dwarf stars; da stars; general relativity
Quick-look Pipeline Lightcurves for 9.1 Million Stars Observed over the First Year of the TESS Extended Mission

We present a magnitude-limited set of lightcurves for stars observed over the Transiting Exoplanet Survey Satellite (TESS) Extended Mission, as extracted from full-frame images (FFIs) by MIT's Quick-Look Pipeline (QLP). QLP uses multi-aperture photometry to produce lightcurves for ~1 million stars each 27.4 days sector, which are then searched for exoplanet transits. The per-sector lightcurves for 9.1 million unique targets observed over the first year of the Extended Mission (Sectors 27-39) are available as High-Level Science Products (HLSPs) on the Mikulski Archive for Space Telescopes. As in our TESS Primary Mission QLP HLSP delivery, our available data products include both raw and detrended flux time series for all observed stars brighter than TESS magnitude T = 13.5, providing the community with one of the largest sources of FFI-extracted lightcurves to date.

Keywords: light curves; transit photometry; exoplanets