adsabs/SciX_UAT_keywords huggingface dataset:
Nightside Ionospheric Structure and Composition on Mars Driven by Energetic Electron Precipitation

Ionospheric chemistry plays an unexpectedly important role in the evolution of planetary habitability. This study is dedicated to a detailed modeling of the nightside Martian ionospheric structure and composition, a topic that has been poorly explored due to the absence of relevant measurements, but now becomes tractable owing to the unprecedented measurements made by the Mars Atmosphere and Volatile Evolution. Two-stream kinetic calculations and time-dependent fluid calculations are coupled to derive the nightside density profiles at 100-300 km for a large number of ion species, assuming solar wind electron precipitation as the only viable ionizing source in the ideal nonmagnetized atmosphere. Our calculations indicate the presence of a well-defined ionospheric peak at 146 km with a peak density of 8500 cm-3, as driven by the strong atmospheric "absorption" of precipitating electrons at low altitudes. The distribution of nonterminal species is roughly under chemical equilibrium below 170 km, whereas for terminal species such as NO+ and HCO+, diffusion is effective at essentially all altitudes, in direct contrast to the dayside behavior. In the more realistic magnetized atmosphere, the ionospheric peak seldom exists due to the patchiness of electron precipitation. In particular, our model results agree fairly well with the MAVEN measurements, especially in view of the coincidence between electron depletion and thermal plasma void seen along many MAVEN orbits. Compared to the dayside, the nightside ionospheric composition has a much higher proportion of NO+ and lower proportion of CO2 +, likely indicative of nightside enhancement of atmospheric O and N.

Keywords: mars; planetary ionospheres; planetary atmospheres
Asteroid 16 Psyche: Shape, Features, and Global Map

We develop a shape model of asteroid 16 Psyche using observations acquired in a wide range of wavelengths: Arecibo S-band delay-Doppler imaging, Atacama Large Millimeter Array (ALMA) plane-of-sky imaging, adaptive optics (AO) images from Keck and the Very Large Telescope (VLT), and a recent stellar occultation. Our shape model has dimensions 278 (-4/+8 km) × 238(-4/+6 km) × 171 km (-1/+5 km), an effective spherical diameter Deff = 222-1/+4 km, and a spin axis (ecliptic lon, lat) of (36°, -8°) ± 2°. We survey all the features previously reported to exist, tentatively identify several new features, and produce a global map of Psyche. Using 30 calibrated radar echoes, we find Psyche's overall radar albedo to be 0.34 ± 0.08 suggesting that the upper meter of regolith has a significant metal (i.e., Fe-Ni) content. We find four regions of enhanced or complex radar albedo, one of which correlates well with a previously identified feature on Psyche, and all of which appear to correlate with patches of relatively high optical albedo. Based on these findings, we cannot rule out a model of Psyche as a remnant core, but our preferred interpretation is that Psyche is a differentiated world with a regolith composition analogous to enstatite or CH/CB chondrites and peppered with localized regions of high metal concentrations. The most credible formation mechanism for these regions is ferrovolcanism as proposed by Johnson et al. (2020).

Keywords: main belt asteroids; asteroids; asteroid surfaces; radar telescopes; radar astronomy
Coexistence of Martian Proton Aurorae and Proton Cyclotron Waves during the Enhancement of Solar Wind Activity

Due to the lack of a global magnetic field, the charge exchange process between the solar wind protons and Martian hydrogen corona is of critical importance to Mars' atmosphere. The energetic neutral atoms and pickup H+ produced during this process can further excite proton aurorae and proton cyclotron waves (PCWs) in the near-Mars space, for which the observational evidence however remains very limited. Here we report a particular event to show that the PCWs and proton aurorae were simultaneously recorded by the Mars Atmosphere and Volatile EvolutioN spacecraft during 10 consecutive orbits. As the byproducts of the charge exchange process, these two phenomena are found to be highly correlated in both space and time, with the correlation coefficient >0.7 between the auroral emissions and PCW amplitudes. Moreover, the wave and ultraviolet measurements show clearly that both the PCWs and proton aurora events tend to occur more frequently and intensively within the stream interaction region, as being strongly modulated by the solar wind activity. Our results indicate that the solar wind can directly transport energy and particles into the near-Mars environment, leading to the simultaneous enhancements of plasma wave activity and proton precipitation, which therefore helps comprehend the significant role of the solar wind activity and charge exchange process in driving the energy budget to the Martian upper atmosphere.

Keywords: mars; aurorae; charge exchange ionization; solar-planetary interactions
The MOSDEF Survey: The Evolution of the Mass-Metallicity Relation from z = 0 to z 3.3

We investigate the evolution of galaxy gas-phase metallicity (O/H) over the range z = 0-3.3 using samples of ~300 galaxies at z ~ 2.3 and ~150 galaxies at z ~ 3.3 from the MOSDEF survey. This analysis crucially utilizes different metallicity calibrations at z ~ 0 and z > 1 to account for evolving interstellar medium (ISM) conditions. We find significant correlations between O/H and stellar mass (M*) at z ~ 2.3 and z ~ 3.3. The low-mass power-law slope of the mass-metallicity relation (MZR) is remarkably invariant over z = 0-3.3, such that O/H ∝ ${M}_{* }^{0.30}$ at all redshifts in this range. At fixed M*, O/H decreases with increasing redshift as dlog(O/H)/dz = -0.11 ± 0.02. We find no evidence that the fundamental metallicity relation between M*, O/H, and star formation rate evolves out to z ~ 3.3. We employ analytic chemical evolution models to place constraints on the mass and metal loading factors of galactic outflows. The efficiency of metal removal increases toward lower M* at fixed redshift and toward higher redshift at fixed M*. These models suggest that the slope of the MZR is primarily set by the scaling of the outflow metal loading factor with M*, not by the change in gas fraction as a function of M*. The evolution toward lower O/H at fixed M* with increasing redshift is driven by both higher gas fraction (leading to stronger dilution of ISM metals) and higher metal removal efficiency. These results suggest that the processes governing the smooth baryonic growth of galaxies via gas flows and star formation hold in the same form over at least the past 12 Gyr. * Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: galaxy evolution; galaxy chemical evolution; high-redshift galaxies; galaxy abundances; chemical abundances; metallicity; galaxy winds; emission line galaxies
Spatial Distribution of the Origin of Umbral Waves in a Sunspot Umbra

Umbral flashes (UFs) are emissions in the core of chromospheric lines caused by upward propagating waves steepening into shocks. UFs are followed by an expanding blueshifted umbral wave and redshifted plasma returning to the initial state. Here we use 5 s cadence images acquired at ±0.04 nm off the H ${}_{\alpha }$ line center by the Visible Imaging Spectrometer installed on the Goode Solar Telescope (GST) to detect the origin of UFs and umbral waves (UWs) in a sunspot with a uniform umbra free of light bridges and clusters of umbral dots. The data showed that UFs do not randomly originate over the umbra. Instead, they appear to be repeatedly triggered at locations with the lowest umbral intensity and the most powerful oscillations of H ${}_{\alpha }$ -0.04 nm intensity. GST magnetic field measurements using the Near-Infrared Imaging Spectropolarimeter also showed that the dominant location of prevalent UF origin is cospatial associated with the strongest fields in the umbra. Interface Region Imaging Spectrograph 149.0 nm images showed that no bright UV loops were anchored in the umbra in general, and near the UF patches in particular, suggesting that UFs and UWs alone cannot be responsible for the origin of warm coronal loops. We thus conclude that the existence of locations with prevalent origin of UFs confirms the idea that they may be driven by a subsurface source located near the axis of a flux rope, while the presence of several UFs trigger centers may indicate the complex structure of a sunspot umbra.

Keywords: sunspots; solar photosphere; solar chromosphere
OGLE-2019-BLG-0960 Lb: the Smallest Microlensing Planet

We report the analysis of OGLE-2019-BLG-0960, which contains the smallest mass-ratio microlensing planet found to date (q = 1.2-1.6 × 10-5 at 1σ). Although there is substantial uncertainty in the satellite parallax measured by Spitzer, the measurement of the annual parallax effect combined with the finite source effect allows us to determine the mass of the host star (ML = 0.3-0.6 M⊙), the mass of its planet (mp = 1.4-3.1 M⊕), the projected separation between the host and planet (a⊥ = 1.2-2.3 au), and the distance to the lens system (DL = 0.6-1.2 kpc). The lens is plausibly the blend, which could be checked with adaptive optics observations. As the smallest planet clearly below the break in the mass-ratio function, it demonstrates that current experiments are powerful enough to robustly measure the slope of the mass-ratio function below that break. We find that the cross-section for detecting small planets is maximized for planets with separations just outside of the boundary for resonant caustics and that sensitivity to such planets can be maximized by intensively monitoring events whenever they are magnified by a factor A > 5. Finally, an empirical investigation demonstrates that most planets showing a degeneracy between (s > 1) and (s < 1) solutions are not in the regime ( $| \mathrm{log}s| \gg 0$ ) for which the "close"/"wide" degeneracy was derived. This investigation suggests that there is a link between the "close"/"wide" and "inner/outer" degeneracies and also that the symmetry in the lens equation goes much deeper than symmetries uncovered for the limiting cases.

Keywords: gravitational microlensing exoplanet detection
V346 Nor: The Post-outburst Life of a Peculiar Young Eruptive Star

FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased accretion is often accompanied by collimated jets and energetic, large-scale molecular outflows. The extra heating during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar material, affecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010 due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradual re-brightening of V346 Nor, with its Ks-band brightness only 1.5 mag below the outburst brightness level. Our Very Large Telescope (VLT)/XSHOOTER spectroscopic observations display several strong forbidden emission lines toward the source from various metals and molecular hydrogen, suggesting the launch of a new jet. Our N-band spectrum obtained with VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar medium has changed in the post-outburst period compared to peak brightness.

Keywords: star formation; circumstellar matter; infrared astronomy
New or Increased Cometary Activity in (2060) 95P/Chiron

Asteroid Terrestrial-impact Last Alert System (ATLAS) observations of Centaur (2060) 95P/Chiron show a brightening in the apparent magnitude not due rotational light curves or phase effects. This onset or enhancement of cometary activity started after 2021 February 8 UT and continued in later observations from 2021 June 18 UT onward. Recent ATLAS observations and deeper follow-up imaging obtained using the Las Cumbres Observatory 1.0 m robotic telescope network find no confirmed signature of coma or tail-like features.

Keywords: centaur group; coma dust; wide-field telescopes; comets; sky surveys
Backward Population Synthesis: Mapping the Evolutionary History of Gravitational-wave Progenitors

One promising way to extract information about stellar astrophysics from a gravitational-wave catalog is to compare the catalog to the outputs of stellar population synthesis modeling with varying physical assumptions. The parameter space of physical assumptions in population synthesis is high-dimensional and the choice of parameters that best represents the evolution of a binary system may depend in an as-yet-to-be-determined way on the system's properties. Here we propose a pipeline to simultaneously infer zero-age main-sequence properties and population synthesis parameter settings controlling modeled binary evolution from individual gravitational-wave observations of merging compact binaries. Our pipeline can efficiently explore the high-dimensional space of population synthesis settings and progenitor system properties for each system in a catalog of gravitational-wave observations. We apply our pipeline to observations in the third LIGO-Virgo Gravitational-Wave Transient Catalog. We showcase the effectiveness of this pipeline with a detailed study of the progenitor properties and population synthesis settings that produce mergers like the observed GW150914. Our pipeline permits a measurement of the variation of population synthesis parameter settings with binary properties, if any; we illustrate the possibility of such capability by presenting inferences for the recent GWTC-3 transient catalog that suggest that the stable mass transfer efficiency parameter may vary with primary black hole mass.

Keywords: binary stars; gravitational wave astronomy; astrostatistics; markov chain monte carlo; algorithms; gravitational wave sources; gravitational waves
Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe

Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with "rough" magnetic fields, I.e., fields with atypically large spatial derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; I.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study this statistical correlation closer to the corona. As a first step, we analyze the separate correlation properties of the EPs measured by the Integrated Science Investigation of the Sun (IS⊙IS) instruments during the first solar encounter. The distribution of time intervals between a specific type of event, I.e., the waiting time, can indicate the nature of the underlying process. We find that the IS⊙IS observations show a power-law distribution of waiting times, indicating a correlated (non-Poisson) distribution. Analysis of low-energy (∼15 - 200 keV/nuc) IS⊙IS data suggests that the results are consistent with the 1 au studies, although we find hints of some unexpected behavior. A more complete understanding of these statistical distributions will provide valuable insights into the origin and propagation of solar EPs, a picture that should become clear with future PSP orbits.

Keywords: solar energetic particles; interplanetary turbulence; interplanetary physics; interplanetary magnetic fields; solar wind; slow solar wind
An Optical Study of the Black Widow Population

The optical study of the heated substellar companions of black widow (BW) millisecond pulsars (MSPs) provides unique information on the MSP particle and radiation output and on the neutron star mass. Here we present an analysis of optical photometry and spectroscopy of a set of relatively bright BWs, many newly discovered in association with Fermi γ-ray sources. Interpreting the optical data requires sophisticated models of the companion heating. We provide a uniform analysis, selecting the preferred heating model and reporting on the companion masses and radii, the pulsar heating power, and neutron star mass. The substellar companions are substantially degenerate, with average densities 15-30× Solar, but are inflated above their zero temperature radii. We find evidence that the most extreme recycled BW pulsars have both large >0.8M ⊙ accreted mass and low <108G magnetic fields. Examining a set of heavy BWs, we infer that neutron star masses larger than 2.19M ⊙ (1σ confidence) or 2.08M ⊙ (3σ confidence) are required; these bounds exclude all but the stiffest equations of state in standard tabulations.

Keywords: neutron stars
Cross Correlation between the Thermal Sunyaev-Zeldovich Effect and the Integrated Sachs-Wolfe Effect

We present a joint cosmological analysis of the power spectra measurement of the Planck Compton parameter and the integrated Sachs-Wolfe (ISW) maps. We detect the statistical correlation between the Planck thermal Sunyaev-Zeldovich (tSZ) map and ISW data with a significance of a 3.6σ confidence level (CL), with the autocorrelation of the Planck tSZ data being measured at a 25σ CL. The joint auto- and cross-power spectra constrain the matter density to be ${{\rm{\Omega }}}_{{\rm{m}}}={0.317}_{-0.031}^{+0.040}$ , the Hubble constant to be ${H}_{0}={66.5}_{-1.9}^{+2.0}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ , and the rms matter density fluctuations to be ${\sigma }_{8}={0.730}_{-0.037}^{+0.040}$ at the 68% CL. The derived large-scale structure S 8 parameter is ${S}_{8}\equiv {\sigma }_{8}{({{\rm{\Omega }}}_{{\rm{m}}}/0.3)}^{0.5}=0.755\pm 0.060$ . If using only the diagonal blocks of covariance matrices, the Hubble constant becomes ${H}_{0}={69.7}_{-1.5}^{+2.0}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ . In addition, we obtain the constraint of the product of the gas bias, gas temperature, and density as ${b}_{\mathrm{gas}}\left({T}_{{\rm{e}}}/(0.1\,\mathrm{keV})\right)\left({\bar{n}}_{{\rm{e}}}/1\,{{\rm{m}}}^{-3}\right)={3.09}_{-0.380}^{+0.320}$ . We find that this constraint leads to an estimate on the electron temperature today as ${T}_{{\rm{e}}}=({2.40}_{-0.300}^{+0.250})\times {10}^{6}\,{\rm{K}}$ , consistent with the expected temperature of the warm-hot intergalactic medium. Our studies show that the ISW-tSZ cross correlation is capable of probing the properties of the large-scale diffuse gas.

Keywords: large-scale structure of the universe
A New Method to Constrain the Appearance and Disappearance of Observed Jellyfish Galaxy Tails

We present a new approach for observationally constraining where the tails of Jellyfish (JF) galaxies in groups and clusters first appear and how long they remain visible for with respect to the moment of their orbital pericenter. This is accomplished by measuring the distribution of their tail directions, with respect to their host centers, and their distribution in a projected velocity-radius phase-space diagram. We then model these observed distributions using a fast and flexible approach, where JF tails are painted onto dark matter halos, according to a simple parameterized prescription, before a Bayesian analysis is performed to estimate the parameters. We demonstrate the effectiveness of our approach using observational mocks, then apply it to a known observational sample of 106 JF galaxies, with radio-continuum tails located inside 68 hosts such as groups and clusters. We find that, typically, the radio-continuum tails become visible on first infall, when the galaxy reaches roughly three-quarters of r 200, and the tails remain visible for a few hundred Myr after pericenter passage. Lower-mass galaxies in more massive hosts tend to form visible tails further out and their tails disappear more quickly after pericenter. We argue that this indicates that they are more sensitive to ram pressure stripping. With upcoming large-area surveys of JF galaxies in progress, this is a promising new method for constraining the environmental conditions in which visible JF tails exist.

Keywords: orbits; galaxy clusters; galaxy evolution; galaxy tails; galaxy groups; radio continuum emission; galaxy dark matter halos
Theoretical and Observational Evidence for Coriolis Effects in Coronal Magnetic Fields via Direct Current Driven Flaring Events

All stars produce explosive surface events such as flares and coronal mass ejections. These events are driven by the release of energy stored in coronal magnetic fields, generated by the stellar dynamo. However, it remains unclear if the energy deposition in the magnetic fields is driven by direct or alternating currents. Recently, we presented observational measurements of the flare intensity distributions for a sample of ~105 stars across the main sequence observed by TESS, all of which exhibited power-law distributions similar to those observed in the Sun, albeit with varying slopes. Here we investigate the mechanisms required to produce such a distribution of flaring events via direct current energy deposition, in which coronal magnetic fields braid, reconnect, and produce flares. We adopt a topological model for this process, which produces a power-law distribution of energetic flaring events. We expand this model to include the Coriolis effect, which we demonstrate produces a shallower distribution of flare energies in stars that rotate more rapidly (corresponding to a weaker decline in occurrence rates toward increasing flare energies). We present tentative evidence for the predicted rotation-power-law index correlation in the observations. We advocate for future observations of stellar flares that would improve our measurements of the power-law exponents, and yield key insights into the underlying dynamo mechanisms that underpin the self-similar flare intensity distributions.

Keywords: emerging flux tubes; solar dynamo; solar magnetic reconnection; optical flares