82 research outputs found
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Aurora: A generalized retrieval framework for exoplanetary transmission spectra
Atmospheric retrievals of exoplanetary transmission spectra provide important
constraints on various properties such as chemical abundances, cloud/haze
properties, and characteristic temperatures, at the day-night atmospheric
terminator. To date, most spectra have been observed for giant exoplanets due
to which retrievals typically assume H-rich atmospheres. However, recent
observations of mini-Neptunes/super-Earths, and the promise of upcoming
facilities including JWST, call for a new generation of retrievals that can
address a wide range of atmospheric compositions and related complexities. Here
we report Aurora, a next-generation atmospheric retrieval framework that builds
upon state-of-the-art architectures and incorporates the following key
advancements: a) a generalised compositional retrieval allowing for H-rich and
H-poor atmospheres, b) a generalised prescription for inhomogeneous
clouds/hazes, c) multiple Bayesian inference algorithms for high-dimensional
retrievals, d) modular considerations for refraction, forward scattering, and
Mie-scattering, and e) noise modeling functionalities. We demonstrate Aurora on
current and/or synthetic observations of hot Jupiter HD209458b, mini-Neptune
K218b, and rocky exoplanet TRAPPIST1d. Using current HD209458b spectra, we
demonstrate the robustness of our framework and cloud/haze prescription against
assumptions of H-rich/H-poor atmospheres, improving on previous treatments.
Using real and synthetic spectra of K218b, we demonstrate the agnostic approach
to confidently constrain its bulk atmospheric composition and obtain precise
abundance estimates. For TRAPPIST1d, 10 JWST NIRSpec transits can enable
identification of the main atmospheric component for cloud-free CO-rich and
N-rich atmospheres, and abundance constraints on trace gases including
initial indications of O if present at enhanced levels (10-100x Earth
levels)
Recommended from our members
Aurora: A generalized retrieval framework for exoplanetary transmission spectra
Atmospheric retrievals of exoplanetary transmission spectra provide important
constraints on various properties such as chemical abundances, cloud/haze
properties, and characteristic temperatures, at the day-night atmospheric
terminator. To date, most spectra have been observed for giant exoplanets due
to which retrievals typically assume H-rich atmospheres. However, recent
observations of mini-Neptunes/super-Earths, and the promise of upcoming
facilities including JWST, call for a new generation of retrievals that can
address a wide range of atmospheric compositions and related complexities. Here
we report Aurora, a next-generation atmospheric retrieval framework that builds
upon state-of-the-art architectures and incorporates the following key
advancements: a) a generalised compositional retrieval allowing for H-rich and
H-poor atmospheres, b) a generalised prescription for inhomogeneous
clouds/hazes, c) multiple Bayesian inference algorithms for high-dimensional
retrievals, d) modular considerations for refraction, forward scattering, and
Mie-scattering, and e) noise modeling functionalities. We demonstrate Aurora on
current and/or synthetic observations of hot Jupiter HD209458b, mini-Neptune
K218b, and rocky exoplanet TRAPPIST1d. Using current HD209458b spectra, we
demonstrate the robustness of our framework and cloud/haze prescription against
assumptions of H-rich/H-poor atmospheres, improving on previous treatments.
Using real and synthetic spectra of K218b, we demonstrate the agnostic approach
to confidently constrain its bulk atmospheric composition and obtain precise
abundance estimates. For TRAPPIST1d, 10 JWST NIRSpec transits can enable
identification of the main atmospheric component for cloud-free CO-rich and
N-rich atmospheres, and abundance constraints on trace gases including
initial indications of O if present at enhanced levels (10-100x Earth
levels)
LRG-BEASTS: Evidence for clouds in the transmission spectrum of HATS-46 b
We have performed low-resolution ground-based spectroscopy of HATS-46 b in
transmission, using the EFOSC2 instrument on the ESO New Technology Telescope
(NTT). HATS-46 b is a highly-inflated exoplanet that is a prime target for
transmission spectroscopy, having a Jupiter-like radius (0.95 R)
but a much lower mass (0.16 M). It orbits a G-type star with a
4.7 d period, giving an equilibrium temperature of 1100 K. We observed one
transit of HATS-46 b with the NTT, with the time-series spectra covering a
wavelength range of 3900 - 9000 Angstrom at a resolution of . We
achieved a remarkably precise transmission spectrum of 1.03 photon
noise, with a median uncertainty of ppm for Angstrom wide
bins, despite the relative faintness of the host star with . The transmission spectrum does not show strong absorption features and
retrievals favour a cloudy model, ruling out a clear atmosphere with
confidence. We also place a conservative upper limit on the sodium
abundance under the alternative scenario of a clear atmosphere. This is the
eighth planet in the LRG-BEASTS survey, which uses 4m-class telescopes such as
the NTT to obtain low-resolution transmission spectra of hot Jupiters with
precisions of around one atmospheric scale height.Comment: 10 pages, 7 figures, 4 tables, accepted for publication in MNRA
The GTC exoplanet transit spectroscopy survey IX. Detection of haze, Na, K, and Li in the super-Neptune WASP-127b
Exoplanets with relatively clear atmospheres are prime targets for detailed
studies of chemical compositions and abundances in their atmospheres. Alkali
metals have long been suggested to exhibit broad wings due to pressure
broadening, but most of the alkali detections only show very narrow absorption
cores, probably because of the presence of clouds. We report the strong
detection of the pressure-broadened spectral profiles of Na, K, and Li
absorption in the atmosphere of the super-Neptune WASP-127b, at 4.1,
5.0, and 3.4, respectively. We performed a spectral retrieval
modeling on the high-quality optical transmission spectrum newly acquired with
the 10.4 m Gran Telescopio Canarias (GTC), in combination with the re-analyzed
optical transmission spectrum obtained with the 2.5 m Nordic Optical Telescope
(NOT). By assuming a patchy cloudy model, we retrieved the abundances of Na, K,
and Li, which are super-solar at 3.7 for K and 5.1 for Li (and
only 1.8 for Na). We constrained the presence of haze coverage to be
around 52%. We also found a hint of water absorption, but cannot constrain it
with the global retrieval owing to larger uncertainties in the probed
wavelengths. WASP-127b will be extremely valuable for atmospheric
characterization in the era of James Webb Space Telescope
Spatially-resolved high-resolution retrievals of Ultra-hot Jupiters
Stars and planetary system
Spatially resolving the terminator: variation of Fe, temperature, and winds in WASP-76 b across planetary limbs and orbital phase
Interstellar matter and star formatio
Methane Throughout the Atmosphere of the Warm Exoplanet WASP-80b
The abundances of major carbon and oxygen bearing gases in the atmospheres of
giant exoplanets provide insights into atmospheric chemistry and planet
formation processes. Thermochemistry suggests that methane should be the
dominant carbon-bearing species below 1000 K over a range of plausible
atmospheric compositions; this is the case for the Solar System planets and has
been confirmed in the atmospheres of brown dwarfs and self-luminous directly
imaged exoplanets. However, methane has not yet been definitively detected with
space-based spectroscopy in the atmosphere of a transiting exoplanet, but a few
detections have been made with ground-based, high-resolution transit
spectroscopy including a tentative detection for WASP-80b. Here we report
transmission and emission spectra spanning 2.4-4.0 micrometers of the 825 K
warm Jupiter WASP-80b taken with JWST's NIRCam instrument, both of which show
strong evidence for methane at greater than 6-sigma significance. The derived
methane abundances from both viewing geometries are consistent with each other
and with solar to sub-solar C/O and ~5 solar metallicity, which is
consistent with theoretical predictions.Comment: 23 pages, 10 figures, 3 tables. This preprint has been submitted to
and accepted in principle for publication in Nature without significant
change
Awesome SOSS: atmospheric characterization of WASP-96 b using the JWST early release observations
This is the final version. Available on open access from Oxford University Press via the DOI in this recordData availability: All data used in this study are publicly available from the Barbara A. Mikulski Archive for Space Telescopes;
https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. The models generated in this paper can be made available on request.The newly operational JWST offers the potential to study the atmospheres of distant worlds with precision that has not been achieved before. One of the first exoplanets observed by JWST in the summer of 2022 was WASP-96 b, a hot Saturn orbiting a G8 star. As a part of the Early Release Observations programme, one transit of WASP-96 b was observed with NIRISS/SOSS to capture its transmission spectrum from 0.6 to 2.85 μm. In this work, we utilize four retrieval frameworks to report precise and robust measurements of WASP-96 b's atmospheric composition. We constrain the logarithmic volume mixing ratios of multiple chemical species in its atmosphere, including: H2O =, CO2 =, and K =, thus generally consistent with 1× solar (with the exception of CO2). Notably, our results offer a first abundance constraint on potassium in WASP-96 b's atmosphere and important inferences on carbon-bearing species such as CO2 and CO. Our short wavelength NIRISS/SOSS data are best explained by the presence of an enhanced Rayleigh scattering slope, despite previous inferences of a clear atmosphere - although we find no evidence for a grey cloud deck. Finally, we explore the data resolution required to appropriately interpret observations using NIRISS/SOSS. We find that our inferences are robust against different binning schemes. That is, from low R = 125 to the native resolution of the instrument, the bulk atmospheric properties of the planet are consistent. Our systematic analysis of these exquisite observations demonstrates the power of NIRISS/SOSS to detect and constrain multiple molecular and atomic species in the atmospheres of hot giant planets
The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultra Hot Jupiter WASP-18 b
We present high-resolution dayside thermal emission observations of the
exoplanet WASP-18b using IGRINS on Gemini South. We remove stellar and telluric
signatures using standard algorithms, and we extract the planet signal via
cross correlation with model spectra. We detect the atmosphere of WASP-18b at a
signal-to-noise ratio (SNR) of 5.9 using a full chemistry model, measure H2O
(SNR=3.3), CO (SNR=4.0), and OH (SNR=4.8) individually, and confirm previous
claims of a thermal inversion layer. The three species are confidently detected
(>4) with a Bayesian inference framework, which we also use to retrieve
abundance, temperature, and velocity information. For this ultra-hot Jupiter
(UHJ), thermal dissociation processes likely play an important role. Retrieving
abundances constant with altitude and allowing the temperature-pressure profile
to freely adjust results in a moderately super-stellar carbon to oxygen ratio
(C/O=0.75^{+0.14}_{-0.17}) and metallicity ([M/H]=1.03^{+0.65}_{-1.01}).
Accounting for undetectable oxygen produced by thermal dissociation leads to
C/O=0.45^{+0.08}_{-0.10} and [M/H]=1.17^{+0.66}_{-1.01}. A retrieval that
assumes radiative-convective-thermochemical-equilibrium and naturally accounts
for thermal dissociation constrains C/O<0.34 (2) and
[M/H]=0.48^{+0.33}_{-0.29}, in line with the chemistry of the parent star.
Looking at the velocity information, we see a tantalising signature of
different Doppler shifts at the level of a few km/s for different molecules,
which might probe dynamics as a function of altitude and location on the planet
disk. Our results demonstrate that ground-based, high-resolution spectroscopy
at infrared wavelengths can provide meaningful constraints on the compositions
and climate of highly irradiated planets. This work also elucidates potential
pitfalls with commonly employed retrieval assumptions when applied to UHJ
spectra.Comment: 27 pages, 18 figures, submitted to AAS Journals. Community feedback
welcom
Awesome SOSS: Transmission Spectroscopy of WASP-96b with NIRISS/SOSS
The future is now - after its long-awaited launch in December 2021, JWST
began science operations in July 2022 and is already revolutionizing exoplanet
astronomy. The Early Release Observations (ERO) program was designed to provide
the first images and spectra from JWST, covering a multitude of science cases
and using multiple modes of each on-board instrument. Here, we present
transmission spectroscopy observations of the hot-Saturn WASP-96b with the
Single Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and
Slitless Spectrograph, observed as part of the ERO program. As the SOSS mode
presents some unique data reduction challenges, we provide an in-depth
walk-through of the major steps necessary for the reduction of SOSS data:
including background subtraction, correction of 1/f noise, and treatment of the
trace order overlap. We furthermore offer potential routes to correct for field
star contamination, which can occur due to the SOSS mode's slitless nature. By
comparing our extracted transmission spectrum with grids of atmosphere models,
we find an atmosphere metallicity between 1x and 5x solar, and a solar
carbon-to-oxygen ratio. Moreover, our models indicate that no grey cloud deck
is required to fit WASP-96b's transmission spectrum, but find evidence for a
slope shortward of 0.9m, which could either be caused by enhanced Rayleigh
scattering or the red wing of a pressure-broadened Na feature. Our work
demonstrates the unique capabilities of the SOSS mode for exoplanet
transmission spectroscopy and presents a step-by-step reduction guide for this
new and exciting instrument.Comment: MNRAS, in press. Updated to reflect published versio
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