adsabs/SciX_UAT_keywords huggingface dataset:
As the Worlds Turn: Constraining Spin Evolution in the Planetary-mass Regime

To understand how planetary spin evolves and traces planet formation processes, we measure rotational line broadening in eight planetary-mass objects (PMOs) of various ages (1-800 Myr) using near-infrared high-resolution spectra from NIRSPEC/Keck. Combining these with published rotation rates, we compile 27 PMO spin velocities, 16 of which derive from our NIRSPEC/Keck program. Our data are consistent with spin velocities v scaling with planetary radius R as v ∝ 1/R. We conclude that spin angular momentum is conserved as objects cool and contract over the sampled age range. The PMOs in our sample spin at rates that are approximately an order of magnitude below their break-up values, consistent with the hypothesis that they were spun down by magnetized circum-PMO disks (CPDs) during the formation era at ages ≲a few Myr. There is a factor of 4-5 variation in spin velocity that has yet to be understood theoretically. It also remains to be seen whether spin evolves on timescales ≳1 Gyr for PMOs, as it does for stars and high-mass brown dwarfs emitting magnetized winds.

Keywords: high resolution spectroscopy; exoplanet formation
Uranium Abundances and Ages of r-process Enhanced Stars with Novel U II Lines

The ages of the oldest stars shed light on the birth, chemical enrichment, and chemical evolution of the universe. Nucleocosmochronometry provides an avenue to determining the ages of these stars independent from stellar-evolution models. The uranium abundance, which can be determined for metal-poor r-process enhanced (RPE) stars, has been known to constitute one of the most robust chronometers known. So far, U abundance determination has used a single U II line at λ3859 Å. Consequently, U abundance has been reliably determined for only five RPE stars. Here, we present the first homogeneous U abundance analysis of four RPE stars using two novel U II lines at λ4050 Å and λ4090 Å, in addition to the canonical λ3859 Å line. We find that the U II lines at λ4050 Å and λ4090 Å are reliable and render U abundances in agreement with the λ3859 U abundance, for all of the stars. We, thus, determine revised U abundances for RPE stars, 2MASS J09544277+5246414, RAVE J203843.2-002333, HE 1523-0901, and CS 31082-001, using multiple U II lines. We also provide nucleocosmochronometric ages of these stars based on the newly derived U, Th, and Eu abundances. The results of this study open up a new avenue to reliably and homogeneously determine U abundance for a significantly larger number of RPE stars. This will, in turn, enable robust constraints on the nucleocosmochronometric ages of RPE stars, which can be applied to understand the chemical enrichment and evolution in the early universe, especially of r-process elements. *Some of the data presented herein were 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Additionally, this work is based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program IDs 275.D-5028(A), 077.D-0453(A), and 165.N-0276(A). This paper also includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: stellar abundances; cosmochronology; stellar atmospheres; population ii stars; r-process
Radioactive Heating Rate of r-process Elements and Macronova Light Curve

We study the heating rate of r-process nuclei and thermalization of decay products in neutron star merger ejecta and macronova (kilonova) light curves. Thermalization of charged decay products, I.e., electrons, α-particles, and fission fragments, is calculated according to their injection energy. The γ-ray thermalization processes are also properly calculated by taking the γ-ray spectrum of each decay into account. We show that the β-decay heating rate at later times approaches a power-law decline as ∝t-2.8, which agrees with the result of Waxman et al. We present a new analytic model to calculate macronova light curves, in which the density structure of the ejecta is accounted for. We demonstrate that the observed bolometric light curve and temperature evolution of the macronova associated with GW170817 are reproduced well by the β-decay heating rate with the solar r-process abundance pattern. We interpret the break in the observed bolometric light curve around a week as a result of the diffusion wave crossing a significant part of the ejecta rather than a thermalization break. We also show that the time-weighted integral of the bolometric light curve (Katz integral) is useful to provide an estimate of the total r-process mass from the observed data, which is independent of the highly uncertain radiative transfer. For the macronova in GW170817, the ejecta mass is robustly estimated as ≈0.05 M⊙ for Amin ≤ 72 and 85 ≤ Amin ≤ 130 with the solar r-process abundance pattern. The code for computation of the heating rate and light curve for given initial nuclear abundances is publicly available.

Keywords: compact binary stars; gravitational wave astronomy; r-process
Observing Planet-driven Dust Spirals with ALMA

Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of thermal emission from the dust component of protoplanetary disks have revealed an abundance of substructures that may be interpreted as evidence for embedded planets, but planet-driven spiral arms-perhaps one of the most compelling lines of evidence-have proven comparatively elusive. In this work, we test the capabilities of ALMA to detect the planet-driven spiral signal in continuum emission. Carrying out hydrodynamic simulations and radiative transfer calculations, we present synthetic Band 7 continuum images for a wide range of disk and observing conditions. We show that thermal mass planets at tens of astronomical units typically drive spirals detectable within a few hours of integration time, and the detectable planet mass may be as low as ~Neptune mass (0.3 M th). The grains probed by ALMA form spirals morphologically identical to the underlying gas spiral. The temperature of the dust spiral is crucial in determining its contrast, and spirals are easier to detect in disks with an adiabatic equation of state and longer cooling times. Resolving the spiral is not necessary for its detection; with the help of residual maps, the optimal beam size is a few times the spiral width at a constant noise level. Finally, we show how the presence of gaps and rings can impair our ability to recognize colocated spirals. Our work demonstrates the planet-finding potential of the current design specification of ALMA, and suggests that observing capability is not the bottleneck in searching for spirals induced by thermal mass planets.

Keywords: planet formation; protoplanetary disks; planetary-disk interactions
An Experimental Study of Chemical Desorption for Phosphine in Interstellar Ice

Phosphine (PH3), an important molecule for the chemistry of phosphorus (P)-bearing species in the interstellar medium (ISM) is considered to form primarily on interstellar grains. However, no report exists on the processes of PH3 formation on grains. Here, we experimentally studied the reactions of hydrogen (H) atoms and PH3 molecules on compact amorphous solid water, with a particular focus on the chemical desorption of PH3 at 10-30 K. After exposure to H atoms for 120 minutes, up to 50% of solid PH3 was lost from the icy surface. On the basis of experiments using deuterium atoms, it was concluded that the loss of PH3 resulted from chemical desorption through the reactions PH3 + H → PH2 + H2 and/or PH2 + H → PH3. The effective desorption cross-section was ∼5 × 10-17 cm2, which is three times larger than that of hydrogen sulfide measured under similar experimental conditions. The present results suggest that the formation of PH3, and possibly PH2 and PH, followed by their desorption from icy grains, may contribute to the formation of PN and PO in the gas phase, and thus may play a role in the P chemistry of the ISM.

Keywords: dense interstellar clouds; interstellar dust processes; astrochemistry; pre-biotic astrochemistry
The Hawaii Infrared Parallax Program. VI. The Fundamental Properties of 1000+ Ultracool Dwarfs and Planetary-mass Objects Using Optical to Mid-infrared Spectral Energy Distributions and Comparison to BT-Settl and ATMO 2020 Model Atmospheres

We derive the bolometric luminosities (L bol) of 865 field-age and 189 young ultracool dwarfs (spectral types M6-T9, including 40 new discoveries presented here) by directly integrating flux-calibrated optical to mid-infrared (MIR) spectral energy distributions (SEDs). The SEDs consist of low-resolution (R ~ 150) near-infrared (NIR; 0.8-2.5μm) spectra (including new spectra for 97 objects), optical photometry from the Pan-STARRS1 survey, and MIR photometry from the CatWISE2020 survey and Spitzer/IRAC. Our L bol calculations benefit from recent advances in parallaxes from Gaia, Spitzer, and UKIRT, as well as new parallaxes for 19 objects from CFHT and Pan-STARRS1 presented here. Coupling our L bol measurements with a new uniform age analysis for all objects, we estimate substellar masses, radii, surface gravities, and effective temperatures (T eff) using evolutionary models. We construct empirical relationships for L bol and T eff as functions of spectral type and absolute magnitude, determine bolometric corrections in optical and infrared bandpasses, and study the correlation between evolutionary model-derived surface gravities and NIR gravity classes. Our sample enables a detailed characterization of BT-SETTL and ATMO 2020 atmospheric model systematics as a function of spectral type and position in the NIR color-magnitude diagram. We find the greatest discrepancies between atmospheric and evolutionary model-derived T eff (up to 800 K) and radii (up to 2.0 R Jup) at the M/L spectral type transition boundary. With 1054 objects, this work constitutes the largest sample to date of ultracool dwarfs with determinations of their fundamental parameters.

Keywords: fundamental parameters of stars; astrometry; exoplanet atmospheres; stellar evolutionary models; bolometric correction; photometry; spectral energy distribution; brown dwarfs; t dwarfs; m dwarf stars; l dwarfs; stellar atmospheres
Magnetic Helicity Flux across Solar Active Region Photospheres. I. Hemispheric Sign Preference in Solar Cycle 24

A hemispheric preference in the dominant sign of magnetic helicity has been observed in numerous features in the solar atmosphere, i.e., left-handed/right-handed helicity in the northern/southern hemisphere. The relative importance of different physical processes that may contribute to the observed hemispheric sign preference (HSP) of magnetic helicity is still under debate. Here, we estimate magnetic helicity flux (dH/dt) across the photospheric surface for 4802 samples of 1105 unique active regions (ARs) that appeared over an 8 yr period from 2010 to 2017 during solar cycle 24, using photospheric vector magnetic field observations by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The estimates of dH/dt show that 63% and 65% of the investigated AR samples in the northern and southern hemispheres, respectively, follow the HSP. We also find a trend that the HSP of dH/dt increases from ∼50%-60% up to ∼70%-80% as ARs (1) appear at the earlier inclining phase of the solar cycle or higher latitudes and (2) have larger values of $| {dH}/{dt}| $ , the total unsigned magnetic flux, and the average plasma-flow speed. These observational findings support the enhancement of the HSP mainly by the Coriolis force acting on a buoyantly rising and expanding flux tube through the turbulent convection zone. In addition, the differential rotation on the solar surface as well as the tachocline α-effect of a flux-transport dynamo may reinforce the HSP for ARs at higher latitudes.

Keywords: solar magnetic fields; solar active region magnetic fields; solar activity; solar photosphere; solar active region velocity fields; astronomy data analysis
Thermodynamic and Energetic Limits on Continental Silicate Weathering Strongly Impact the Climate and Habitability of Wet, Rocky Worlds

The "liquid water habitable zone" (HZ) concept is predicated on the ability of the silicate weathering feedback to stabilize climate across a wide range of instellations. However, representations of silicate weathering used in current estimates of the effective outer edge of the HZ accounts for neither the thermodynamic limit on the concentration of weathering products in runoff set by clay precipitation nor the energetic limit on precipitation set by planetary instellation. We find that when the thermodynamic limit is included in an idealized coupled climate/weathering model, the steady-state planetary climate loses sensitivity to silicate dissolution kinetics, becoming sensitive to temperature primarily through the effect of temperature on runoff and to ${\mathrm{pCO}}_{2}$ through an effect on solute concentration mediated by pH. This increases sensitivity to land fraction, ${\mathrm{CO}}_{2}$ outgassing, and geological factors such as soil age and lithology, all of which are found to have a profound effect on the position of the effective outer edge of the HZ. The interplay between runoff sensitivity and the energetic limit on precipitation leads to novel warm states in the outer reaches of the HZ, owing to the decoupling of temperature and precipitation. We discuss strategies for detecting the signature of the silicate weathering feedback through exoplanet observations in light of insights derived from the revised picture of weathering.

Keywords: habitable planets; habitable zone; exoplanet atmospheres; exoplanet evolution
Flaring and Spot Activities on the Semi-detached Binary System KIC 06852488

The continuous and unbroken time-series photometry data of Kepler and the Transiting Exoplanet Survey Satellite (TESS) provide a good opportunity to study the continuous variations in the light curve of binary stars. This paper reports the discoveries of the correlation between the two maxima on the light curve of KIC 06852488 and the correlation between the O'Connell effect and the O - C curve. The Max I and Max II vary with a same cycle length of ∼2000 days and a 180° phase difference, and the variation of the Max II coincides with the O - C curve of the primary light minima. After analyzing the Kepler and TESS light curves, it is detected that this binary is a semi-detached system with a mass ratio of 0.4622(±0.0036). The secondary component is filling its critical Roche lobe, while the primary component is only filling 12.25(±0.10)% of the lobe volume that contributes more than 85% luminosity of the total system. The variation of the O'Connell effect could be explained by an evolving hot spot on the primary component and an evolving cool spot on the secondary component. It is found that their positions are symmetrical with the inner Lagrange L1 point. After subtracting the binary brightness changes, six optical flares are detected that come from the cool secondary. We calculated the energy of flares and found that all of the flares are superflares. Both the flares and an evolving dark spot on the lobe-filling secondary component make the system a very interesting source to investigate the effects of binary interaction on the magnetic activities.

Keywords: close binary stars; eclipsing binary stars; eclipsing binary minima timing method; pulsating variable stars
Toward Precision Cosmology with Improved Planetary Nebula Luminosity Function Distances Using VLT-MUSE. II. A Test Sample from Archival Data

Thanks to the MUSE integral field spectrograph on board the Very Large Telescope (VLT), extragalactic distance measurements with the [O III] λ5007 planetary nebula luminosity function (PNLF) are now possible out to ∼40 Mpc. Here we analyze the VLT/MUSE data for 20 galaxies from the ESO public archive to identify the systems' planetary nebulae (PNe) and determine their PNLF distances. Three of the galaxies do not contain enough PNe for a robust measure of the PNLF, and the results for one other system are compromised of the galaxy's internal extinction. However, we obtain robust PNLF distances for the remaining 16 galaxies, two of which are isolated and beyond 30 Mpc in a relatively unperturbed Hubble flow. From these data, we derive a Hubble constant of 74.2 ± 7.2 (stat) ±3.7 (sys) km s‑1 Mpc‑1, a value that is very similar to that found from other quality indicators (e.g., Cepheids, the tip of the red giant branch, and surface brightness fluctuations). At present, the uncertainty is dominated by the small number of suitable galaxies in the ESO archive and their less-than-ideal observing conditions and calibrations. Based on our experience with these systems, we identify the observational requirements necessary for the PNLF to yield a competitive value for H 0 that is independent of the Type Ia supernova distance scale.

Keywords: galaxies; distance indicators; hubble constant; planetary nebulae
Spatial Variation in Strong Line Ratios and Physical Conditions in Two Strongly Lensed Galaxies at z 1.4

Upcoming space-based integral field spectrographs will enable spatially resolved spectroscopy of distant galaxies, including at the scale of individual star-forming regions (i.e., down to just tens of parsecs) in galaxies that have been strongly gravitationally lensed. In the meantime, there is only a very small set of lensed galaxies where such spatial detail is possible at wavelengths containing important rest-optical emission lines, even with the Hubble Space Telescope's Wide Field Camera 3 infrared channel grisms. Here, we examine two of these sources, SDSS J1723+3411 and SDSS J2340+2947, using HST WFC3/IR grism data and supporting spatially unresolved spectroscopy from several ground-based instruments to explore the size of spatial variations in observed strong emission-line ratios like O32 and R23, which are sensitive to ionization parameter and metallicity, and the Balmer decrement, which is an indicator of reddening. We find significant spatial variation in the reddening and in the reddening-corrected O32 and R23 values that correspond to spreads of a few tenths of a dex in ionization parameter and metallicity. We also find clear evidence of a negative radial gradient in star formation in SDSS J2340+2947 and tentative evidence of one in SDSS J1723+3411, though its star formation is quite asymmetric. Finally, we find that reddening can vary enough spatially to make spatially resolved reddening corrections necessary in order to characterize gradients in line ratios and the physical conditions inferred from them, necessitating the use of space-based integral field units for future work on larger, more statistically robust samples.

Keywords: high-redshift galaxies; interstellar medium; strong gravitational lensing; galaxy properties
Physical Constraints on the Extended Interstellar Medium of the z = 6.42 Quasar J1148+5251: [C II]158 μm, [N II]205 μm, and [O I]146 μm Observations

We report new Northern Extended Millimeter Array observations of the [C II]158 μm, [N II]205 μm, and [O I]146 μm atomic fine structure lines (FSLs) and dust continuum emission of J1148+5251, a z = 6.42 quasar, which probe the physical properties of its interstellar medium (ISM). The radially averaged [C II]158 μm and dust continuum emission have similar extensions (up to $\theta ={2.51}_{-0.25}^{+0.46}\ \mathrm{arcsec}$ , corresponding to $r={9.8}_{-2.1}^{+3.3}\ \mathrm{kpc}$ , accounting for beam convolution), confirming that J1148+5251 is the quasar with the largest [C II]158 μm-emitting reservoir known at these epochs. Moreover, if the [C II]158 μm emission is examined only along its NE-SW axis, a significant excess (>5.8σ) of [C II]158 μm emission (with respect to the dust) is detected. The new wide-bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad [C II]158 μm line wings that were reported in previous studies. We also report the first detection of the [O I]146 μm and (tentatively) [N II]205 μm emission lines in J1148+5251. Using FSL ratios of the [C II]158 μm, [N II]205 μm, [O I]146 μm, and previously measured [C I]369 μm emission lines, we show that J1148+5251 has similar ISM conditions compared to lower-redshift (ultra)luminous infrared galaxies. CLOUDY modeling of the FSL ratios excludes X-ray-dominated regions and favors photodissociation regions as the origin of the FSL emission. We find that a high radiation field (103.5-4.5 G 0), a high gas density (n ≃ 103.5-4.5 cm-3), and an H I column density of 1023 cm-2 reproduce the observed FSL ratios well.

Keywords: quasars; high-redshift galaxies; interstellar medium; interferometry; millimeter astronomy
The Possible Tidal Demise of Kepler's First Planetary System

We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet (1.1R J, 5.9M J) orbiting an evolved host star (2.9R ⊙, 1.5M ⊙). Using transit timing measurements from Kepler, Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate $\dot{P}={131}_{-22}^{+20}$ ms yr-1, corresponding to an infall timescale $P/\dot{P}\approx 2.5\,\mathrm{Myr}$ . We consider other explanations for the data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed period derivative implies a tidal quality factor ${Q}_{\star }^{{\prime} }={2.50}_{-0.62}^{+0.85}\times {10}^{4}$ , in good agreement with theoretical predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new benchmark for understanding tidal physics at the end of the planetary life cycle.

Keywords: exoplanet astronomy; exoplanet evolution; exoplanet dynamics; exoplanet tides; transits; timing variation methods; hot jupiters
Toward the Unambiguous Identification of Supermassive Binary Black Holes through Bayesian Inference

Supermassive binary black holes at subparsec orbital separations have yet to be discovered, with the possible exception of blazar OJ 287. In parallel to the global hunt for nanohertz gravitational waves from supermassive binaries using pulsar timing arrays, there has been a growing sample of candidates reported from electromagnetic surveys, particularly searches for periodic variations in the optical light curves of quasars. However, the periodicity search is prone to false positives from quasar red noise and quasiperiodic oscillations from the accretion disk of a single supermassive black hole, especially when the data span fewer than a few signal cycles. We present a Bayesian method for the detection of quasar (quasi)periodicity in the presence of red noise. We apply this method to the binary candidate PG 1302-102 and show that (a) there is very strong support (Bayes factor >106) for quasiperiodicity and (b) the data slightly favor a quasiperiodic oscillation over a sinusoidal signal, which we interpret as modest evidence against the binary black hole hypothesis. We also find that the prevalent damped random walk red-noise model is disfavored with more than 99.9% credibility. Finally, we outline future work that may enable the unambiguous identification of supermassive binary black holes.

Keywords: supermassive black holes; quasars; galaxy mergers; bayesian statistics