adsabs/SciX_UAT_keywords huggingface dataset:
On the Statistics of Elsasser Increments in Solar Wind and Magnetohydrodynamic Turbulence

In this Letter we investigate the dependency with scale of the empirical probability distribution functions (PDF) of Elsasser increments using large sets of WIND data (collected between 1995 and 2017) near 1 au. The empirical PDF are compared to the ones obtained from high-resolution numerical simulations of steadily driven, homogeneous reduced MHD turbulence on a 20483 rectangular mesh. A large statistical sample of Alfvénic increments is obtained by using conditional analysis based on the solar wind average properties. The PDF tails obtained from observations and numerical simulations are found to have exponential behavior in the inertial range, with an exponential decrement that satisfies power laws of the form α l ∝ l -μ , where l is the scale size, with μ between 0.17 and 0.25 for observations and 0.43 for simulations. PDF tails were extrapolated assuming their exponential behavior extends to arbitrarily large increments in order to determine structure function scaling laws at very high orders. Our results point to potentially universal scaling laws governing the PDF of Elsasser increments and to an alternative approach to investigate high-order statistics in solar wind observations.

Keywords: magnetohydrodynamics; interplanetary turbulence; solar wind
The Hybrid Debris Disk Host Star HD 21997 is a High-frequency Delta Scuti Pulsator

HD 21997 is host to a prototypical "hybrid" debris disk characterized by debris disk-like dust properties and a CO gas mass comparable to a protoplanetary disk. We use Transiting Exoplanet Survey Satellite time series photometry to demonstrate that HD 21997 is a high-frequency delta Scuti pulsator. If the mode identification can be unambiguously determined in future works, an asteroseismic age of HD 21997 may become feasible.

Keywords: delta scuti variable stars; stellar pulsations; variable stars
YZiCS: Unveiling the Quenching History of Cluster Galaxies Using Phase-space Analysis

We used the time since infall (TSI) of galaxies, obtained from the Yonsei Zoom-in Cluster Simulation, and the star formation rate (SFR) from the Sloan Digital Sky Survey Data Release 10 to study how quickly the star formation of disk galaxies is quenched in cluster environments. We first confirm that both simulated and observed galaxies are consistently distributed in phase space. We then hypothesize that the TSI and SFR are causally connected; thus, both the TSI and SFR of galaxies at each position of phase space can be associated through abundance matching. Using a flexible model, we derive the star formation history (SFH) of cluster galaxies that best reproduces the relationship between the TSI and SFR at z ∼ 0.08. According to this SFH, we find that galaxies with M* > 109.5 M⊙ generally follow the so-called "delayed-then-rapid" quenching pattern. Our main results are as follows: (I) part of the quenching takes place outside clusters through mass quenching and preprocessing. The e-folding timescale of this "ex situ quenching phase" is roughly 3 Gyr with a strong inverse mass dependence. (II) The pace of quenching is maintained roughly for 2 Gyr ("delay time") during the first crossing time into the cluster. During the delay time, quenching remains gentle, probably because gas loss happens primarily on hot and neutral gases. (III) Quenching becomes more dramatic (e-folding timescale of roughly 1 Gyr) after delay time, probably because ram pressure stripping is strongest near the cluster center. Counterintuitively, more massive galaxies show shorter quenching timescales mainly because they enter their clusters with lower gas fractions due to ex situ quenching.

Keywords: galaxy evolution
Rotational Mass Shedding from Asteroid (6478) Gault

The ∼4 km diameter main belt asteroid 6478 Gault has ejected dust intermittently since at least 2013. The character of the emission, including its episodic nature and the low speed of the ejected particles (V ∼ 0.15 m s-1), is most consistent with mass loss from a body rotating near rotational breakup. Owing to dust contamination of the nucleus signal, this conclusion had not yet been confirmed. To test this idea, we have obtained new images of Gault in 2020 August in the absence of dust. Our photometry shows a lightcurve with a very small amplitude (maximum ∼0.05 mag) and a periodicity of 2.55 ± 0.10 hr. The new observations are consistent with a model in which Gault is rotating near breakup, with centrifugal forces responsible for its episodic mass loss. Approximated as a strengthless (fluid) spherical body, the implied density is ρ = 1700 kg m-3. We use the Froude number Fr, defined here as the ratio between centrifugal force and gravitational force, as a way to investigate mass-loss regimes in fast-spinning asteroids and find that mass shedding starts at Fr ∼ 0.5.

Keywords: asteroids; small solar system bodies
Radio Power from a Direct-collapse Black Hole in CR7

The leading contenders for the seeds of the first quasars are direct-collapse black holes (DCBHs) formed during catastrophic baryon collapse in atomically cooled halos at z ∼ 20. The discovery of the Lyα emitter CR7 at z = 6.6 was initially held to be the first detection of a DCBH, although this interpretation has since been challenged on the grounds of Spitzer IRAC and Very Large Telescope X-Shooter data. Here we determine if radio flux from a DCBH in CR7 could be detected and discriminated from competing sources of radio emission in the halo such as young supernovae and H II regions. We find that a DCBH would emit a flux of 10-200 nJy at 1.0 GHz, far greater than the sub-nJy signal expected for young supernovae but on par with continuum emission from star-forming regions. However, radio emission from a DCBH in CR7 could be distinguished from free-free emission from H II regions by its spectral evolution with frequency and could be detected by the Square Kilometre Array in the coming decade.

Keywords: supermassive black holes; intermediate-mass black holes; primordial galaxies; high-redshift galaxies; population iii stars; quasars; early universe; reionization
Follow-up on the Supermassive Black Hole Binary Candidate J1048+7143: Successful Prediction of the Next Gamma-Ray Flare and Refined Binary Parameters in the Framework of the Jet Precession Model

Analyzing single-dish and very long baseline interferometry radio, as well as Fermi Large Area Telescope γ-ray observations, we explained the three major flares in the γ-ray light curve of FSRQ J1048+7143 with the spin–orbit precession of the dominant mass black hole in a supermassive black hole binary system. Here, we report on the detection of a fourth γ-ray flare from J1048+7143, appearing in the time interval that was predicted in our previous work. Including this new flare, we constrained the mass ratio into a narrow range of 0.062 < q < 0.088, and consequently we were able to further constrain the parameters of the hypothetical supermassive binary black hole at the heart of J1048+7143. We predict the occurrence of the fifth major γ-ray flare that would appear only if the jet will still lay close to our line of sight. The fourth major γ-ray flare also shows the two-subflare structure, further strengthening our scenario in which the occurrence of the subflares is the signature of the precession of a spine–sheath jet structure that quasiperiodically interacts with a proton target, e.g., clouds in the broad-line region.

Keywords: active galactic nuclei; blazars
Heating of the Atmospheres of Short-orbit Exoplanets by Their Rapid Orbital Motion through an Extreme Space Environment

Exoplanets with short orbit periods reside very close to their host stars. They transition very rapidly between different sectors of the circumstellar space environment along their orbit, leading to large variations of the magnetic field in the vicinity of the planet on short timescales. This rapid change of the magnetic flux through the conducting and resistive layer of the planetary upper atmosphere may drive currents that dissipate in the form of Joule heating (JH). Here, we estimate the amount of JH dissipation in the upper atmosphere of Trappist-1e, and two hypothetical planets orbiting the Sun in close-in orbits. We find that the rapid orbital motion could drive a significant amount of atmospheric heating and could significantly affect the planetary atmosphere escape rate. Thus, the process should be accounted for when studying the long-term evolution of exoplanetary atmospheres.

Keywords: exoplanet atmospheres; exoplanet atmospheric evolution; planetary ionospheres
Measuring White Dwarf Variability from Sparsely Sampled Gaia DR3 Multi-epoch Photometry

White dwarf stars are ubiquitous in the Galaxy, and are essential to understanding stellar evolution. While most white dwarfs are photometrically stable and reliable flux standards, some can be highly variable, which can reveal unique details about the endpoints of low-mass stellar evolution. In this study, we characterize a sample of high-confidence white dwarfs with multi-epoch photometry from Gaia Data Release 3. We compare these Gaia light curves with light curves from the Zwicky Transiting Facility and the Transiting Exoplanet Survey Satellite to see when Gaia data independently can accurately measure periods of variability. From this sample, 105 objects have variability periods measured from the Gaia light curves independently, with periods as long as roughly 9.5 days and as short as 256.2 s (roughly 4 minutes), including seven systems with periods shorter than 1000 s. We discover 86 new objects from the 105 target samples, including pulsating, spotted, and binary white dwarfs, and even a new 68.4 minute eclipsing cataclysmic variable. The median amplitude of the absolute photometric variability we confirm from Gaia independently is 1.4%, demonstrating that Gaia epoch photometry is capable of measuring short-term periods even when observations are sparse.

Keywords: white dwarf stars; periodic variable stars; light curves
Disk or Companion: Characterizing Excess Infrared Flux in Seven White Dwarf Systems with Near-infrared Spectroscopy

Excess infrared flux from white dwarf stars is likely to arise from a dusty debris disk or a cool companion. In this work, we present near-infrared spectroscopic observations with Keck/MOSFIRE, Gemini/GNIRS, and Gemini/Flamingos-2 of seven white dwarfs with infrared excesses identified in previous studies. We confirmed the presence of dust disks around four white dwarfs (Gaia J0611-6931, Gaia J0006+2858, Gaia J2100+2122, and WD 0145+234) as well as two new white dwarf-brown dwarf pairs (Gaia J0052+4505 and Gaia J0603+4518). In three of the dust disk systems, we detected for the first time near-infrared metal emissions (Mg I, Si I, and possibly Fe I) from a gaseous component of the disk. We developed a new Markov Chain Monte Carlo framework to constrain the geometric properties of each dust disk. In three systems, the dust disk and the gas disk appear to coincide spatially. For the two brown dwarf-white dwarf pairs, we identified broad molecular absorption features typically seen in L dwarfs. The origin of the infrared excess around Gaia J0723+6301 remains a mystery. Our study underlines how near-infrared spectroscopy can be used to determine sources of infrared excess around white dwarfs, which has now been detected photometrically in hundreds of systems.

Keywords: infrared spectroscopy; infrared excess; brown dwarfs; white dwarf stars; debris disks
The Turbulent Properties of the Sub-Alfvénic Solar Wind Measured by the Parker Solar Probe

For the first time, Parker Solar Probe (PSP) observed the sub-Alfvénic solar wind where the solar wind bulk speed drops below the local Alfvén speed for an extended period of time. Here, we report on the turbulent properties of the sub-Alfvénic region. We analyze the turbulence correlation length and the energy transfer and compare the results with nearby super-Alfvénic regions. As the Alfvén speed is larger or comparable to the solar wind speed in the intervals studied, we use a modified Taylor's hypothesis to account for wave propagation. We find that the wave propagation speed affects the analysis of the correlation lengths of the forward and backward propagating z ± modes. In the sub-Alfvénic region, the correlation length of the z - mode is shorter than that of the outward propagating z + mode, although the correlation time of the z - mode is about 10 times larger than that of the z + mode. For the energy transfer, we use both incompressible and compressible formulations to calculate the energy flux based on third-order structure functions. The incompressible energy cascade rates for the forward and backward propagating modes are computed separately using the modified Taylor's hypothesis. The averaged compressible cascade rate is higher in the sub-Alfvénic interval than the nearby downstream super-Alfvénic region, which may be due to the lower fluctuation amplitude in the latter super-Alfvénic interval. Longer incursions of the PSP in the sub-Alfvénic winds in the future will give us better statistics.

Keywords: solar wind; interplanetary turbulence
WIYN Open Cluster Study. LXXXV. Li in NGC 2243: Implications for Stellar and Galactic Evolution

High-dispersion spectra in the Li λ6708 region have been obtained and analyzed in the old, metal-deficient cluster NGC 2243. From Hydra spectra for 29 astrometric and radial velocity members, we derive rotational velocities, as well as [Fe/H], [Ca/H], [Si/H], and [Ni/H] based on 17, 1, 1, and 3 lines, respectively. Using ROBOSPECT, an automatic equivalent width measurement program, we derive [Fe/H] = -0.54 ± 0.11 (MAD), for an internal precision for the cluster [Fe/H] below 0.03 dex. Given the more restricted line set, comparable values for [Ca/H], [Si/H], and [Ni/H] are -0.48 ± 0.19, -0.44 ± 0.11, and -0.61 ± 0.06, respectively. With E(B - V) = 0.055, appropriate isochrones imply (m - M) = 13.2 ± 0.1 and an age of 3.6 ± 0.2 Gyr. Using available VLT spectra and published Li abundances, we construct an Li sample of over 100 stars extending from the tip of the giant branch to 0.5 mag below the Li dip. The Li dip is well populated and, when combined with results for NGC 6819 and Hyades/Praesepe, implies a mass/metallicity slope of 0.4 M⊙/dex for the high-mass edge of the Li dip. The A(Li) distribution among giants reflects the degree of Li variation among the turnoff stars above the Li dip, itself a function of stellar mass and metallicity and strongly anticorrelated with a vrot distribution that dramatically narrows with age. Potential implications of these patterns for the interpretation of Li among dwarf and giant field populations, especially selection biases tied to age and metallicity, are discussed.

Keywords: open star clusters; stellar abundances
Collapsars as Sites of r-process Nucleosynthesis: Systematic Photometric Near-infrared Follow-up of Type Ic-BL Supernovae

One of the open questions following the discovery of GW170817 is whether neutron star (NS) mergers are the only astrophysical sites capable of producing r-process elements. Simulations have shown that 0.01–0.1 M ⊙ of r-process material could be generated in the outflows originating from the accretion disk surrounding the rapidly rotating black hole that forms as a remnant to both NS mergers and collapsing massive stars associated with long-duration gamma-ray bursts (collapsars). The hallmark signature of r-process nucleosynthesis in the binary NS merger GW170817 was its long-lasting near-infrared (NIR) emission, thus motivating a systematic photometric study of the light curves of broad-lined stripped-envelope (Ic-BL) supernovae (SNe) associated with collapsars. We present the first systematic study of 25 SNe Ic-BL—including 18 observed with the Zwicky Transient Facility and 7 from the literature—in the optical/NIR bands to determine what quantity of r-process material, if any, is synthesized in these explosions. Using semi-analytic models designed to account for r-process production in SNe Ic-BL, we perform light curve fitting to derive constraints on the r-process mass for these SNe. We also perform independent light curve fits to models without the r-process. We find that the r-process-free models are a better fit to the light curves of the objects in our sample. Thus, we find no compelling evidence of r-process enrichment in any of our objects. Further high-cadence infrared photometric studies and nebular spectroscopic analysis would be sensitive to smaller quantities of r-process ejecta mass or indicate whether all collapsars are completely devoid of r-process nucleosynthesis.

Keywords: supernovae; nucleosynthesis; transient sources; r-process; explosive nucleosynthesis; time domain astronomy; surveys; optical astronomy; photometry; light curves; infrared photometry; gamma-ray bursts
X-Ray through Very High Energy Intrabinary Shock Emission from Black Widows and Redbacks

Black widow and redback systems are compact binaries in which a millisecond pulsar heats and may even ablate its low-mass companion by its intense wind of relativistic particles and radiation. In such systems, an intrabinary shock can form as a site of particle acceleration and associated nonthermal emission. We model the X-ray and gamma-ray synchrotron and inverse Compton spectral components for select spider binaries, including diffusion, convection, and radiative energy losses in an axially symmetric, steady-state approach. Our new multizone code simultaneously yields energy-dependent light curves and orbital-phase-resolved spectra. Using parameter studies and matching the observed X-ray spectra and light curves, as well as Fermi Large Area Telescope spectra where available, with a synchrotron component, we can constrain certain model parameters. For PSR J1723-2837 these are notably the magnetic field and bulk flow speed of plasma moving along the shock tangent, the shock acceleration efficiency, and the multiplicity and spectrum of pairs accelerated by the pulsar. This affords a more robust prediction of the expected high-energy and very high energy gamma-ray flux. We find that nearby pulsars with hot or flaring companions may be promising targets for the future Cerenkov Telescope Array. Moreover, many spiders are likely to be of significant interest to future MeV-band missions such as AMEGO and e-ASTROGAM.

Keywords: millisecond pulsars; close binary stars; non-thermal radiation sources; gamma-ray astronomy; stellar winds
The COS-Holes Survey: Connecting Galaxy Black Hole Mass with the State of the CGM

We present an analysis of Hubble Space Telescope COS/G160M observations of C IV in the inner circumgalactic medium (CGM) of a novel sample of eight z ∼ 0, L ≈ L ⋆ galaxies, paired with UV-bright QSOs at impact parameters (R proj) between 25 and 130 kpc. The galaxies in this stellar-mass-controlled sample (log10 M ⋆/M ⊙ ∼ 10.2–10.9 M ⊙) host supermassive black holes (SMBHs) with dynamically measured masses spanning log10 M BH/M ⊙ ∼ 6.8–8.4; this allows us to compare our results with models of galaxy formation where the integrated feedback history from the SMBH alters the CGM over long timescales. We find that the C IV column density measurements (N C IV; average log10 N C IV,CH = 13.94 ± 0.09 cm‑2) are largely consistent with existing measurements from other surveys of N C IV in the CGM (average log10 N C IV,Lit = 13.90 ± 0.08 cm‑2), but do not show obvious variation as a function of the SMBH mass. By contrast, specific star formation rate (sSFR) is highly correlated with the ionized content of the CGM. We find a large spread in sSFR for galaxies with log10 M BH/M ⊙ > 7.0, where the CGM C IV content shows a clear dependence on galaxy sSFR but not M BH. Our results do not indicate an obvious causal link between CGM C IV and the mass of the galaxy's SMBH; however, through comparisons to the EAGLE, Romulus25, and IllustrisTNG simulations, we find that our sample is likely too small to constrain such causality.

Keywords: galaxy formation; circumgalactic medium; quasar absorption line spectroscopy
First BISTRO Observations of the Dark Cloud Taurus L1495A-B10: The Role of the Magnetic Field in the Earliest Stages of Low-mass Star Formation

We present BISTRO Survey 850 μm dust emission polarization observations of the L1495A-B10 region of the Taurus molecular cloud, taken at the James Clerk Maxwell Telescope (JCMT). We observe a roughly triangular network of dense filaments. We detect nine of the dense starless cores embedded within these filaments in polarization, finding that the plane-of-sky orientation of the core-scale magnetic field lies roughly perpendicular to the filaments in almost all cases. We also find that the large-scale magnetic field orientation measured by Planck is not correlated with any of the core or filament structures, except in the case of the lowest-density core. We propose a scenario for early prestellar evolution that is both an extension to, and consistent with, previous models, introducing an additional evolutionary transitional stage between field-dominated and matter-dominated evolution, observed here for the first time. In this scenario, the cloud collapses first to a sheet-like structure. Uniquely, we appear to be seeing this sheet almost face on. The sheet fragments into filaments, which in turn form cores. However, the material must reach a certain critical density before the evolution changes from being field dominated to being matter dominated. We measure the sheet surface density and the magnetic field strength at that transition for the first time and show consistency with an analytical prediction that had previously gone untested for over 50 yr.

Keywords: interstellar magnetic fields; molecular clouds; starlight polarization; collapsing clouds; interstellar filaments
Update on the Systematics in the ALMA Proposal Review Process After Cycle 8

We present an updated analysis of systematics in the Atacama Large Millimeter/submillimeter Array (ALMA) proposal ranks to include the last two ALMA cycles, when significant changes were introduced in the proposal review process. In Cycle 7, the investigator list on the proposal cover sheet was randomized such that the reviewers were aware of the overall proposal team but did not know the identity of the principal investigator (PI). In Cycle 8, ALMA adopted distributed peer review for most proposals and implemented dual-anonymous review for all proposals, in which the identity of the proposal team was not revealed to the reviewers. The most significant change in the systematics in Cycles 7 and 8 compared to previous cycles is related to the experience of PIs in submitting ALMA proposals. PIs that submit a proposal every cycle tend to have ranks that are consistent with average in Cycles 7 and 8, whereas previously they had the best overall ranks. Also, PIs who submitted a proposal for the second time show improved ranks over previous cycles. These results suggest some biases related to the relative prominence of the PI have been present in the ALMA review process. Systematics related to regional affiliation remain largely unchanged in that PIs from Chile, East Asia, and non-ALMA regions tend to have poorer overall ranks than PIs from Europe and North America. The systematics of how one region ranks proposals from another region are also investigated. No significant differences in the overall ranks based on gender of the PI are observed.

Keywords: telescopes