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Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) : I. Detection of hot neutral sodium at high altitudes on WASP-49b
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Wyttenbach, A., Lovis, C., Ehrenreich, D., Bourrier, V., Pino, L., Allart, R., Astudillo-Defru, N., Cegla, H. M., Heng, K., Lavie, B., Melo, C., Murgas, F., Santerne, A., Ségransan, D., Udry, S. and Pepe, F. (2017) Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) : I. Detection of hot neutral sodium at high altitudes on WASP-49b. Astronomy & Astrophysics, 602 . A36. doi:10.1051/0004-6361/201630063 ISSN 0004-6361.
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Official URL: http://dx.doi.org/10.1051/0004-6361/201630063
Abstract
High-resolution optical spectroscopy during the transit of HD 189733b, a prototypical hot Jupiter, allowed the resolution of the Na i D sodium lines in the planet, giving access to the extreme conditions of the planet upper atmosphere. We have undertaken HEARTS, a spectroscopic survey of exoplanet upper atmospheres, to perform a comparative study of hot gas giants and determine how stellar irradiation affect them. Here, we report on the first HEARTS observations of the hot Saturn-mass planet WASP-49b. We observed the planet with the HARPS high-resolution spectrograph at ESO 3.6 m telescope. We collected 126 spectra of WASP-49, covering three transits of WASP-49b. We analyzed and modeled the planet transit spectrum, while paying particular attention to the treatment of potentially spurious signals of stellar origin. We spectrally resolve the Na i D lines in the planet atmosphere and show that these signatures are unlikely to arise from stellar contamination. The large contrasts of 2.0 ± 0.5% (D2) and 1.8 ± 0.7% (D1) require the presence of hot neutral sodium (2950+400-500 K) at high altitudes (~1.5 planet radius or ~45 000 km). From estimating the cloudiness index of WASP-49b, we determine its atmosphere to be cloud free at the altitudes probed by the sodium lines. WASP-49b is close to the border of the evaporation desert and exhibits an enhanced thermospheric signature with respect to a farther-away planet such as HD 189733b.
| Item Type: | Journal Article | ||||||||
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| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
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| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
| Journal or Publication Title: | Astronomy & Astrophysics | ||||||||
| Publisher: | EDP Sciences | ||||||||
| ISSN: | 0004-6361 | ||||||||
| Official Date: | June 2017 | ||||||||
| Dates: |
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| Volume: | 602 | ||||||||
| Article Number: | A36 | ||||||||
| DOI: | 10.1051/0004-6361/201630063 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Restricted or Subscription Access |
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