ORCID Profile
0000-0002-3555-480X
Current Organisation
CNRS
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Publisher: American Astronomical Society
Date: 26-05-2021
Abstract: We present a study on the spatially scanned spectroscopic observations of the transit of GJ 1132 b, a warm (∼500 K) super-Earth (1.13 R ⊕ ) that was obtained with the G141 grism (1.125–1.650 μ m) of the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. We used the publicly available Iraclis pipeline to extract the planetary transmission spectra from the five visits and produced a precise transmission spectrum. We analyzed the spectrum using the TauREx3 atmospheric retrieval code, with which we show that the measurements do not contain molecular signatures in the investigated wavelength range and are best fit with a flat-line model. Our results suggest that the planet does not have a clear primordial, hydrogen-dominated atmosphere. Instead, GJ 1132 b could have a cloudy hydrogen-dominated atmosphere, have a very enriched secondary atmosphere, be airless, or have a tenuous atmosphere that has not been detected. Due to the narrow wavelength coverage of WFC3, these scenarios cannot be distinguished yet, but the James Webb Space Telescope may be capable of detecting atmospheric features, although several observations may be required to provide useful constraints.
Publisher: American Astronomical Society
Date: 14-08-2020
Publisher: American Astronomical Society
Date: 09-12-2020
Publisher: American Astronomical Society
Date: 22-01-2021
DOI: 10.3847/PSJ/ABD022
Abstract: We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST, and K2 transit-time measurements, and revisit an N -body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets’ densities may be described with a single rocky mass–radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%–5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s −1 , or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers, which we cannot explain with an eighth planet we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system.
Publisher: Springer Science and Business Media LLC
Date: 09-01-2023
DOI: 10.1038/S41586-022-05591-3
Abstract: Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems 1,2 . Access to the chemical inventory of an exoplanet requires high-precision observations, often inferred from in idual molecular detections with low-resolution space-based 3–5 and high-resolution ground-based 6–8 facilities. Here we report the medium-resolution ( R ≈ 600) transmission spectrum of an exoplanet atmosphere between 3 and 5 μm covering several absorption features for the Saturn-mass exoplanet WASP-39b (ref. 9 ), obtained with the Near Infrared Spectrograph (NIRSpec) G395H grating of JWST. Our observations achieve 1.46 times photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO 2 (28.5 σ ) and H 2 O (21.5 σ ), and identify SO 2 as the source of absorption at 4.1 μm (4.8 σ ). Best-fit atmospheric models range between 3 and 10 times solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO 2 , underscore the importance of characterizing the chemistry in exoplanet atmospheres and showcase NIRSpec G395H as an excellent mode for time-series observations over this critical wavelength range 10 .
Publisher: Springer Science and Business Media LLC
Date: 02-09-2022
DOI: 10.1038/S41586-022-05269-W
Abstract: Carbon dioxide (CO 2 ) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO 2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called ‘metallicity’) 1–3 , and thus the formation processes of the primary atmospheres of hot gas giants 4–6 . It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets 7–9 . Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO 2 , but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification 10–12 . Here we present the detection of CO 2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme 13,14 . The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO 2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO 2 , but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models.
Publisher: American Astronomical Society
Date: 09-06-2020
No related grants have been discovered for Jeremy Leconte.