22 research outputs found
Transmission spectroscopy of the lowest-density gas giant: metals and a potential extended outflow in HAT-P-67b
Extremely low-density exoplanets are tantalizing targets for atmospheric
characterization because of their promisingly large signals in transmission
spectroscopy. We present the first analysis of the atmosphere of the
lowest-density gas giant currently known, HAT-P-67 b. This inflated Saturn-mass
exoplanet sits at the boundary between hot and ultrahot gas giants, where
thermal dissociation of molecules begins to dominate atmospheric composition.
We observed a transit of HAT-P-67 b at high spectral resolution with CARMENES
and searched for atomic and molecular species using cross-correlation and
likelihood mapping. Furthermore, we explored potential atmospheric escape by
targeting H and the metastable helium line. We detect Ca II and Na I
with significances of 13.2 and 4.6, respectively. Unlike in
several ultrahot Jupiters, we do not measure a day-to-night wind. The large
line depths of Ca II suggest that the upper atmosphere may be more ionized than
models predict. We detect strong variability in H and the helium
triplet during the observations. These signals suggest the possible presence of
an extended planetary outflow that causes an early ingress and late egress. In
the averaged transmission spectrum, we measure redshifted absorption at the
and level in the H and He I triplet lines,
respectively. From an isothermal Parker wind model, we derive a mass loss rate
of and an outflow temperature of . However, due to the lack of a longer out-of-transit baseline in
our data, additional observations are needed to rule out stellar variability as
the source of the H and He signals.Comment: The Astronomical Journal, in press. 17 pages, 9 figure
Role of breast regression protein 39 (BRP-39)/chitinase 3-like-1 in Th2 and IL-13–induced tissue responses and apoptosis
Mouse breast regression protein 39 (BRP-39; Chi3l1) and its human homologue YKL-40 are chitinase-like proteins that lack chitinase activity. Although YKL-40 is expressed in exaggerated quantities and correlates with disease activity in asthma and many other disorders, the biological properties of BRP-39/YKL-40 have only been rudimentarily defined. We describe the generation and characterization of BRP-39−/− mice, YKL-40 transgenic mice, and mice that lack BRP-39 and produce YKL-40 only in their pulmonary epithelium. Studies of these mice demonstrated that BRP-39−/− animals have markedly diminished antigen-induced Th2 responses and that epithelial YKL-40 rescues the Th2 responses in these animals. The ability of interleukin13 to induce tissue inflammation and fibrosis was also markedly diminished in the absence of BRP-39. Mechanistic investigations demonstrated that BRP-39 and YKL-40 play an essential role in antigen sensitization and immunoglobulin E induction, stimulate dendritic cell accumulation and activation, and induce alternative macrophage activation. These proteins also inhibit inflammatory cell apoptosis/cell death while inhibiting Fas expression, activating protein kinase B/AKT, and inducing Faim 3. These studies establish novel regulatory roles for BRP-39/YKL-40 in the initiation and effector phases of Th2 inflammation and remodeling and suggest that these proteins are therapeutic targets in Th2- and macrophage-mediated disorders
A roadmap to the efficient and robust characterization of temperate terrestrial planet atmospheres with JWST
Ultra-cool dwarf stars are abundant, long-lived, and uniquely suited to
enable the atmospheric study of transiting terrestrial companions with JWST.
Amongst them, the most prominent is the M8.5V star TRAPPIST-1 and its seven
planets, which have been the favored targets of eight JWST Cycle 1 programs.
While Cycle 1 observations have started to yield preliminary insights into the
planets, they have also revealed that their atmospheric exploration requires a
better understanding of their host star. Here, we propose a roadmap to
characterize the TRAPPIST-1 system -- and others like it -- in an efficient and
robust manner. We notably recommend that -- although more challenging to
schedule -- multi-transit windows be prioritized to constrain stellar
heterogeneities and gather up to 2 more transits per JWST hour spent.
We conclude that in such systems planets cannot be studied in isolation by
small programs, thus large-scale community-supported programs should be
supported to enable the efficient and robust exploration of terrestrial
exoplanets in the JWST era
Mining the Ultrahot Skies of HAT-P-70b: Detection of a Profusion of Neutral and Ionized Species
With an equilibrium temperature above 2500 K, the recently discovered
HAT-P-70 b belongs to a new class of exoplanets known as ultra-hot Jupiters:
extremely irradiated gas giants with day-side temperatures that resemble those
found in stars. These ultra-hot Jupiters are among the most amenable targets
for follow-up atmospheric characterization through transmission spectroscopy.
Here, we present the first analysis of the transmission spectrum of HAT-P-70 b
using high-resolution data from the HARPS-N spectrograph of a single transit
event. We use a cross-correlation analysis and transmission spectroscopy to
look for atomic and molecular species in the planetary atmosphere. We detect
absorption by Ca II, Cr I, Cr II, Fe I, Fe II, H I, Mg I, Na I and V I, and we
find tentative evidence of Ca I and Ti II. Overall, these signals appear
blue-shifted by a few km s, suggestive of winds flowing at high velocity
from the day-side to the night-side. We individually resolve the Ca II H & K
lines, the Na I doublet, and the H, H and H Balmer
lines. The cores of the Ca II and H I lines form well above the continuum,
indicating the existence of an extended envelope. We refine the obliquity of
this highly misaligned planet to degrees by examining the
Doppler shadow that the planet casts on its A-type host star. These results
place HAT-P-70 b as one of the exoplanets with the highest number of species
detected in its atmosphere.Comment: 17 pages, 10 figures, accepted to A
Unsupervised Spectral Unmixing For Telluric Correction Using A Neural Network Autoencoder
The absorption of light by molecules in the atmosphere of Earth is a
complication for ground-based observations of astrophysical objects.
Comprehensive information on various molecular species is required to correct
for this so called telluric absorption. We present a neural network autoencoder
approach for extracting a telluric transmission spectrum from a large set of
high-precision observed solar spectra from the HARPS-N radial velocity
spectrograph. We accomplish this by reducing the data into a compressed
representation, which allows us to unveil the underlying solar spectrum and
simultaneously uncover the different modes of variation in the observed spectra
relating to the absorption of and in the
atmosphere of Earth. We demonstrate how the extracted components can be used to
remove and tellurics in a validation observation
with similar accuracy and at less computational expense than a synthetic
approach with molecfit.Comment: Presented at Workshop on Machine Learning and the Physical Sciences
(NeurIPS 2021
Dry or water world? How the water contents of inner sub-Neptunes constrain giant planet formation and the location of the water ice line
In the pebble accretion scenario, the pebbles that form planets drift inward from the outer disk regions, carrying water ice with them. At the water ice line, the water ice on the inward drifting pebbles evaporates and is released into the gas phase, resulting in water-rich gas and dry pebbles that move into the inner disk regions. Large planetary cores can block the inward drifting pebbles by forming a pressure bump outside their orbit in the protoplanetary disk. Depending on the relative position of a growing planetary core relative to the water ice line, water-rich pebbles might be blocked outside or inside the water ice line. Pebbles blocked outside the water ice line do not evaporate and thus do not release their water vapor into the gas phase, resulting in a dry inner disk, while pebbles blocked inside the water ice line release their water vapor into the gas phase, resulting in water vapor diffusing into the inner disk. As a consequence, close-in sub-Neptunes that accrete some gas from the disk should be dry or wet, respectively, if outer gas giants are outside or inside the water ice line, assuming that giant planets form fast, as has been suggested for Jupiter in our Solar System. Alternatively, a sub-Neptune could form outside the water ice line, accreting a large amount of icy pebbles and then migrating inward as a very wet sub-Neptune. We suggest that the water content of inner sub-Neptunes in systems with giant planets that can efficiently block the inward drifting pebbles could constrain the formation conditions of these systems, thus making these sub-Neptunes exciting targets for detailed characterization (e.g., with JWST, ELT, or ARIEL). In addition, the search for giant planets in systems with already characterized sub-Neptunes can be used to constrain the formation conditions of giant planets as well
Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone
Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by
transmission spectroscopy represent a valuable opportunity for detailed
atmospheric characterization and precise chemical abundance constraints. We
present the first optical to infrared (0.3-5 microns) transmission spectrum of
the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The
spectrum is characterized by a 5.1-sigma detection of Na I absorption at 0.59
microns, in which the pressure-broadened wings of the Na D-lines are observed
from space for the first time. A spectral feature at 0.4 microns is tentatively
attributed to SiH at 2.1-sigma confidence. Our retrieval analyses are
consistent with a cloud-free atmosphere without significant contamination from
stellar heterogeneities. We simulate James Webb Space Telescope (JWST)
observations, for a combination of instrument modes, to assess the atmospheric
characterization potential of WASP-62b. We demonstrate that JWST can
conclusively detect Na, H2O, FeH, and SiH within the scope of its Early Release
Science (ERS) program. As the only transiting giant planet currently known in
the JWST Continuous Viewing Zone, WASP-62b could prove a benchmark giant
exoplanet for detailed atmospheric characterization in the James Webb era.Comment: 14 pages, 5 figures, accepted for publication in ApJ