adsabs/SciX_UAT_keywords huggingface dataset:
Resonant Stratification in Titan's Global Ocean

Titan's ice shell floats on top of a global ocean, as revealed by the large tidal Love number k 2 = 0.616 ± 0.067 registered by Cassini. The Cassini observation exceeds the predicted k 2 by one order of magnitude in the absence of an ocean, and is 3σ away from the predicted k 2 if the ocean is pure water resting on top of a rigid ocean floor. Previous studies demonstrate that an ocean heavily enriched in salts (salinity S ≳ 200 g kg-1) can explain the 3σ signal in k 2. Here we revisit previous interpretations of Titan's large k 2 using simple physical arguments and propose a new interpretation based on the dynamic tidal response of a stably stratified ocean in resonance with eccentricity tides raised by Saturn. Our models include inertial effects from a full consideration of the Coriolis force and the radial stratification of the ocean, typically neglected or approximated elsewhere. The stratification of the ocean emerges from a salinity profile where the salt concentration linearly increases with depth. We find multiple salinity profiles that lead to the k 2 required by Cassini. In contrast with previous interpretations that neglect stratification, resonant stratification reduces the bulk salinity required by observations by an order of magnitude, reaching a salinity for Titan's ocean that is compatible with that of Earth's oceans and close to Enceladus' plumes. Consequently, no special process is required to enrich Titan's ocean to a high salinity as previously suggested.

Keywords: titan; saturnian satellites; ocean tides; gravitational fields; planetary interior; astrophysical fluid dynamics; internal waves; galilean satellites; tidal distortion
Ultraviolet Spectroscopy of Lucy Mission Targets with the Hubble Space Telescope

The recently launched Lucy mission aims to understand the dynamical history of the solar system by examining the Jupiter Trojans, a population of primitive asteroids co-orbital with Jupiter. Using the G280 grism on the Hubble Space Telescope's Wide Field Camera 3, we obtained near-ultraviolet spectra of four of the five Lucy mission targets-(617) Patroclus-Menoetius, (11351) Leucus, (3548) Eurybates, and (21900) Orus-to search for novel spectral features. We observe a local reflectance minimum at 0.4 μm accompanied by an increase in reflectance from 0.35 to 0.3 μm in the spectra of Patroclus and Orus. We use the principles of Rayleigh scattering and geometric optics to develop a Hapke optical model to investigate whether this feature can be explained by the presence of submicroscopic grains on Trojan surfaces. The near-ultraviolet "bump" feature can be explained by scattering due to fine-grained opaques (iron, amorphous carbon, or graphite) with grain sizes ranging from 20 to 80 nm.

Keywords: jupiter trojans; near ultraviolet astronomy; hubble space telescope; spectroscopy
Confirmation of Enhanced Long-wavelength Dust Emission in OMC 2/3

Previous continuum observations from the MUSTANG camera on the Green Bank Telescope (GBT) of the nearby star-forming filament OMC 2/3 found elevated emission at 3.3 mm relative to shorter-wavelength data. As a consequence, the inferred dust emissivity index obtained from modified blackbody dust spectra was considerably lower than what is typically measured on ∼0.1 pc scales in nearby molecular clouds. Here we present new observations of OMC 2/3 collected with the MUSTANG-2 camera on the GBT that confirm this elevated emission. We also present for the first time sensitive 1 cm observations made with the Ka-band receiver on the GBT, which also show higher than expected emission. We use these observations - along with Herschel, JCMT, Mambo, and GISMO data - to assemble spectral energy distributions (SEDs) of a variety of structures in OMC 2/3 spanning the range 160 μm to 1 cm. The data at 2 mm and shorter are generally consistent with a modified blackbody spectrum and a single value of β ∼ 1.6. The 3 mm and 1 cm data, however, lie well above such an SED. The spectrum of the long-wavelength excess is inconsistent with both free-free emission and standard "Spinning Dust" models for Anomalous Microwave Emission (AME). The 3 mm and 1 cm data could be explained by a flatter dust emissivity at wavelengths shorter than 2 mm, potentially in concert with AME in some regions.

Keywords: dust continuum emission; interstellar dust; molecular clouds; dense interstellar clouds; interstellar filaments; star formation; protostars
Calibrating the Cepheid Period-Wesenheit Relation in the Gaia Bands Using Galactic Open-cluster Cepheids

Establishing the period-Wesenheit relation requires independent and accurate distance measurements of classical Cepheids (DCEPs). The precise distances provided by associated open clusters independently calibrate the period-Wesenheit relations of DCEPs. 51 DCEPs associated with open clusters are compiled using the constraints of five-dimensional astrometric information. By directly using Gaia data release 3 parallaxes, the period-Wesenheit relation in the Gaia G band is calibrated as ${W}_{G}=(-3.06\pm 0.11)\mathrm{log}P+(-2.96\pm 0.10)$ . Compared with the results derived from directly adopting the DCEP parallaxes or from using distance moduli, the Wesenheit magnitudes based on the cluster-averaged parallaxes exhibit a tighter relation with the period. Besides, there is a systematic offset between the observed Wesenheit absolute magnitudes of distant open-cluster DCEPs and their fitted magnitudes. After considering a parallax zeropoint correction, the systematic offset can be reduced, yielding a probably better period-Wesenheit relation of ${W}_{G}=(-2.94\pm 0.12)\mathrm{log}P+(-2.93\pm 0.11)$ .

Keywords: cepheid variable stars; cepheid distance; open star clusters
Two Transiting Hot Jupiters from the WASP Survey: WASP-150b and WASP-176b

We report the discovery of two transiting exoplanets from the WASP survey, WASP-150b and WASP-176b. WASP-150b is an eccentric (e = 0.38) hot Jupiter on a 5.6 day orbit around a V = 12.03, F8 main-sequence host. The host star has a mass and radius of 1.4 ${M}_{\odot }$ and 1.7 ${R}_{\odot }$ respectively. WASP-150b has a mass and radius of 8.5 ${M}_{{\rm{J}}}$ and 1.1 RJ, leading to a large planetary bulk density of 6.4 ρJ. WASP-150b is found to be ∼3 Gyr old, well below its circularization timescale, supporting the eccentric nature of the planet. WASP-176b is a hot Jupiter planet on a 3.9 day orbit around a V = 12.01, F9 sub-giant host. The host star has a mass and radius of 1.3 M⊙ and 1.9 R⊙. WASP-176b has a mass and radius of 0.86 MJ and 1.5 RJ, respectively, leading to a planetary bulk density of 0.23 ρJ.

Keywords: exoplanet systems; radial velocity; exoplanet detection methods; photometry
Polarization Predictions in the GRB Prompt Phase with the Internal Shock Model

As the standard gamma-ray burst (GRB) prompt-emission model, the internal shock (IS) model can reproduce the fast-rise and slow-decay features of the pulses in the GRB light curve. The time- and energy-dependent polarization can deliver important physical information on the emission region and can be used to test models. Polarization predictions for the GRB prompt phase with the magnetized IS model should be investigated carefully. The magnetic field of the magnetized IS model is very likely to be mixed and decays with radius. The synchrotron emission in the presence of such a decaying magnetic field can recover the Band-like spectrum of the GRB prompt phase. We investigate the dependence of the polarization of GRB prompt emission on both time and energy in the framework of the magnetized IS model. Due to the large range of parameters, it is hard to distinguish the magnetized IS model and the magnetic-reconnection model through polarization degree (PD) curves. The energy-dependent PD could increase toward the high-energy band for the magnetized IS model, while it decreases to zero above the megaelectronvolt band for the dissipative photosphere model. Therefore, we conclude that the energy dependence of PD can be used to distinguish these two models for the GRB prompt emission. Finally, we find that, independent of the observational energy band, the profiles of the ξB - PD curve for the time-integrated and time-resolved PDs are very similar, where ξB is the magnetic field strength ratio of the ordered component to the random component.

Keywords: gamma-ray bursts; magnetic fields
Warm Jupiters Beyond the Tidal Synchronization Limit may Exhibit a Wide Range of Secondary Eclipse Depths

With the JWST we can now characterize the atmospheres of longer-orbit planets, but this moves us into a regime where we cannot assume that tidal forces from the star have eroded the planets' obliquities and synchronized their rotation rates. These rotation vectors may be tracers of formation and evolution histories and also enable a range of atmospheric circulation states. Here we delineate the orbital space over which tidal synchronization and alignment assumptions may no longer apply and present three-dimensional atmospheric models of a hypothetical warm Jupiter over a range of rotation rates and obliquities. We simulate the secondary eclipses of this planet for different possible viewing orientations and times during its orbital, seasonal cycle. We find that the eclipse depth can be strongly influenced by the rotation rate and obliquity through the timing of the eclipse relative to the planet's seasonal cycle, and advise caution in attempting to derive properties such as albedo or day-night transport from this measurement. We predict that if warm Jupiters beyond the tidal limit have intrinsic diversity in their rotation vectors, then this will manifest itself as dispersion in their secondary eclipse depths. We explore eclipse mapping as a way to uniquely constrain the rotation vector of warm Jupiters but find that the associated signals are likely at the edge of the JWST performance. Nevertheless, as the JWST begins to measure the secondary eclipses of longer-orbital-period planets, we should expect to observe the consequences of a wider range of rotation states and circulation patterns.

Keywords: exoplanet atmospheres; atmospheric dynamics; exoplanets; extrasolar gaseous planets; james webb space telescope; eclipses
First Detection of the [O I] 63 μm Emission from a Redshift 6 Dusty Galaxy

We report a ground-based detection of the [O I] 63 μm line in a z = 6.027 gravitationally lensed dusty star-forming galaxy (DSFG) G09.83808 using the Atacama Pathfinder EXperiment SEPIA 660 receiver, the first unambiguous detection of the [O I]63 line beyond redshift 3, and the first obtained from the ground. The [O I]63 line is robustly detected at 22 ± 5 Jy km s-1, corresponding to an intrinsic (de-lensed) luminosity of (5.4 ± 1.3) × 109 L⊙. With the [O I]63/[C II] luminosity ratio of 4, the [O I]63 line is the main coolant of the neutral gas in this galaxy, in agreement with model predictions. The high [O I]63 luminosity compensates for the pronounced [C II] deficit ([C II]/FIR ≃ 4 × 10-4). Using photon-dominated region models, we derive a source-averaged gas density n = 104.0 cm-3, and FUV field strength G = 104 G0, comparable to the z = 2-4 DSFG population. If G09.83808 represents a typical high-redshift DSFG, the [O I]63 line from z = 6 non-lensed DSFGs should be routinely detectable in the Atacama Large Millimeter/submillimeter Array Band 9 observations with ∼15 minutes on-source, opening a new window to study the properties of the earliest DSFGs.

Keywords: submillimeter astronomy; high-redshift galaxies; ultraluminous infrared galaxies
Direct Detection and Characterization of Exoplanets Using Imaging Fourier Transform Spectroscopy

Space-based direct imaging provides prospects for detection and spectral characterization of exoplanets at optical and near-infrared wavelengths. Integral field spectrographs (IFS) have been historically baselined for these mission concepts. However, multiple studies have revealed that detector noise is a serious obstacle for such instruments when observing extremely faint targets such as Earth-like planets. Imaging Fourier transform spectrographs (iFTS) are generally less sensitive to detector noise, and have several other compelling features such as simultaneous imaging and spectroscopy, smaller-format detector requirements, and variable spectral resolving power. To date, they have not been studied as options for such missions. Here, we compare the capabilities of IFS and iFTS for directly obtaining spectra from an Earth-like planet using both analytic and numerical models. Specifically, we compare the required exposure times to achieve the same signal-to-noise ratio with the two architectures over a range of detector and optical system parameters. We find that for a 6 m telescope, an IFS outperforms an iFTS at optical wavelengths due to the effects of distributed photon noise. In the near-IR, the relative efficiency of an IFS and iFTS depends critically on the instrument design and detector noise. An iFTS will be more efficient than an IFS if the readout noise of the near-IR detector is above ∼2–3 e‑ pix‑1 frame‑1 (t frm = 1000 s), which correspond to half to one-third of the state-of-art detector noise. However, if the readout noise is reduced below this threshold, the performance of an IFS will experience a substantial improvement and become more efficient. These results motivate consideration of an iFTS as an alternative option for future direct imaging space missions in the near-IR.

Keywords: direct imaging; spectroscopy; space telescopes
Predictions of the L[C II]-SFR and [CII] Luminosity Function at the Epoch of Reionization

We present the first predictions for the L[C II]-SFR relation and [CII] luminosity function (LF) in the epoch of reionization (EOR) based on cosmological hydrodynamics simulations using the SIMBA suite plus radiative transfer calculations via SÍGAME. The sample consists of 11,137 galaxies covering halo mass log Mhalo ∈ [9, 12.4] M⊙, star formation rate SFR ∈ [0.01, 330] M⊙ yr-1, and metallicity ⟨Zgas⟩SFR ∈ [0.1, 1.9] Z⊙. The simulated L[C II]-SFR relation is consistent with the range observed, but with a spread of ≃0.3 dex at the high end of SFR (>100 M⊙ yr-1) and ≃0.6 dex at the lower end, and there is tension between our predictions and the values of L[C II] above 108.5 L⊙ observed in some galaxies reported in the literature. The scatter in the L[C II]-SFR relation is mostly driven by galaxy properties, such that at a given SFR galaxies with higher molecular mass and metallicity have higher L[C II]. The [CII] LF predicted by SIMBA is consistent with the upper limits placed by the only existing untargeted flux-limited [CII] survey at the EOR and those predicted by semianalytic models. We compare our results with existing models and discuss the differences responsible for the discrepant slopes in the L[C II]-SFR relation.

Keywords: galaxy evolution; galactic and extragalactic astronomy; galaxy properties; interstellar emissions; interstellar medium; hydrodynamical simulations; radiative transfer simulations
Dynamical Mass of the Young Brown Dwarf Companion PZ Tel B

Dynamical masses of giant planets and brown dwarfs are critical tools for empirically validating substellar evolutionary models and their underlying assumptions. We present a measurement of the dynamical mass and an updated orbit of PZ Tel B, a young brown dwarf companion orbiting a late-G member of the β Pic moving group. PZ Tel A exhibits an astrometric acceleration between Hipparcos and Gaia EDR3, which enables the direct determination of the companion's mass. We have also acquired new Keck/NIRC2 adaptive optics imaging of the system, which increases the total baseline of relative astrometry to 15 yr. Our joint orbit fit yields a dynamical mass of ${27}_{-9}^{+25}\,{M}_{\mathrm{Jup}}$ , semimajor axis of ${27}_{-4}^{+14}\,\mathrm{au}$ , eccentricity of ${0.52}_{-0.10}^{+0.08}$ , and inclination of ${91.73}_{-0.32}^{{+0.36}^\circ} $ . The companion's mass is consistent within 1.1σ of predictions from four grids of hot-start evolutionary models. The joint orbit fit also indicates a more modest eccentricity of PZ Tel B than previous results. PZ Tel joins a small number of young (<200 Myr) systems with benchmark substellar companions that have dynamical masses and precise ages from moving group membership.

Keywords: brown dwarfs; direct imaging; astrometry; orbit determination
Dust Directionality and an Anomalous Interplanetary Dust Population Detected by the Parker Solar Probe

Theory and previous space missions indicate there are several populations of zodiacal dust. The most prominent populations are grains on bound elliptic orbits (α-meteoroids), and β-meteoroids on hyperbolic escape trajectories governed largely by their size and composition. Yet, there may be other populations not yet confirmed by observation. The Parker Solar Probe (PSP) spacecraft is able to observe in situ dust populations in the densest part of the zodiacal cloud. Over the first seven orbits, dust count rates are well organized by orbital groups based on orbital parameters of PSP's shrinking orbit. In particular, the first three orbits and the sixth orbit have a single, preperihelion peak in count rate with a gradual drop off postperihelion, while Orbits 4, 5, and 7 have two distinct count rate peaks on either side of perihelion. The secondary peaks in Orbits 4, 5, and 7 are inconsistent with current zodiacal dust models that account for only two dust populations: α- and β-meteoroids. In examining the directionality of dust impacts on the PSP spacecraft, the presence of an anti-ram impactor anomaly postperihelion during Orbit 4 is evident. This anomaly may indicate another dust population beyond the nominal α- and β-meteoroids, and its origin may be related to the Geminids meteoroid stream associated with the asteroid 3200 Phaethon.

Keywords: zodiacal cloud; micrometeoroids
An Investigation of Poorly Studied Open Cluster NGC 4337 Using Multicolor Photometric and Gaia DR2 Astrometric Data

We present a comprehensive analysis (photometric and kinematical) of the poorly studied open cluster NGC 4337 using 2MASS, WISE, APASS, and Gaia DR2 databases. By determining the membership probabilities of stars, we identified the 624 most probable members with membership probability higher than 50% by using proper motion and parallax data taken from Gaia DR2. The mean proper motion of the cluster is obtained as ${\mu }_{x}=-8.83\pm 0.01$ and μy = 1.49 ± 0.006 mas yr-1. We find the normal interstellar extinction toward the cluster region. The radial distribution of members provides a cluster radius of 7'75 (5.63 pc). The estimated age of 1600 ± 180 Myr indicates that NGC 4337 is an old open cluster with a bunch of red giant stars. The overall mass function slope for main-sequence stars is found as $1.46\pm 0.18$ within the mass range 0.75-2.0 ${M}_{\odot }$ , which is in fair agreement with Salpeter's value (x = 1.35) within uncertainty. The present study demonstrates that NGC 4337 is a dynamically relaxed open cluster. Using the Galactic potential model, Galactic orbits are obtained for NGC 4337. We found that this object follows a circular path around the Galactic center. Under the kinematical analysis, we compute the apex coordinates (A, D) by using two methods: (i) the classical convergent point method and (ii) the AD-diagram method. The obtained coordinates are (Aconv, Dconv) = (96°27 ± 0°10, 13°14 ± 0°27) and (A◦, D◦) = (100°282 ± 0°10, 9°577 ± 0°323) respectively. We also computed the Velocity Ellipsoid Parameters, matrix elements (μij), direction cosines (lj, mj, nj), and the Galactic longitude of the vertex (l2).

Keywords: open star clusters; proper motions; hertzsprung russell diagram; stellar mass functions; apex; luminosity function
Rapid Variability of Sgr A* across the Electromagnetic Spectrum

Sagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto the Galactic center black hole. We have analyzed a comprehensive submillimeter (including new observations simultaneous with NIR monitoring), NIR, and 2-8 keV data set. Submillimeter variations tend to lag those in the NIR by ~30 minutes. An approximate Bayesian computation fit to the X-ray first-order structure function shows significantly less power at short timescales in the X-rays than in the NIR. Less X-ray variability at short timescales, combined with the observed NIR-X-ray correlations, means the variability can be described as the result of two strictly correlated stochastic processes, the X-ray process being the low-pass-filtered version of the NIR process. The NIR-X-ray linkage suggests a simple radiative model: a compact, self-absorbed synchrotron sphere with high-frequency cutoff close to NIR frequencies plus a synchrotron self-Compton scattering component at higher frequencies. This model, with parameters fit to the submillimeter, NIR, and X-ray structure functions, reproduces the observed flux densities at all wavelengths, the statistical properties of all light curves, and the time lags between bands. The fit also gives reasonable values for physical parameters such as magnetic flux density B ≈ 13 G, source size L ≈ 2.2RS, and high-energy electron density ne ≈ 4 × 107 cm-3. An animation illustrates typical light curves, and we make public the parameter chain of our Bayesian analysis, the model implementation, and the visualization code.

Keywords: galactic center; astrophysical black holes; supermassive black holes; black hole physics; high energy astrophysics; accretion
Parker Solar Probe Observations of a Dust Trail in the Orbit of (3200) Phaethon

We present the identification and preliminary analysis of a dust trail following the orbit of (3200) Phaethon as seen in white-light images recorded by the Wide-field Imager for Parker Solar Probe (WISPR) instrument on the NASA Parker Solar Probe (PSP) mission. During PSP's first solar encounter in 2018 November, a dust trail following Phaethon's orbit was visible for several days and crossing two fields of view. Preliminary analyses indicate this trail to have a visual magnitude of 15.8 ± 0.3 per pixel and a surface brightness of 25.0 mag arcsec-2 as seen by PSP/WISPR from a distance of ∼0.2 au from the trail. We estimate the total mass of the stream to be ∼(0.4-1.3) × 1012 kg, which is consistent with, though slightly underestimates, the assumed mass of the Geminid stream, but is far larger than the current dust production that Phaethon could support. Our results imply that we are observing a natural clustering of at least some portion of the Geminid meteor stream through its perihelion, as opposed to dust produced more recently from perihelion activity of Phaethon.

Keywords: meteoroid dust clouds; asteroids; near-earth objects; meteor streams; meteor showers; comets