Journal
ASTRONOMY & ASTROPHYSICS
Volume 635, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201936640
Keywords
planets and satellites: atmospheres; planets and satellites: fundamental parameters; instrumentation: spectrographs; planets and satellites: individual: WASP-121b; methods: observational; techniques: spectroscopic
Categories
Funding
- Swiss National Science Foundation (SNSF) of the National Centre for Competence in Research PlanetS
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme [724427, 679633]
- FONDECYT [3180063]
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Ultra-hot Jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres. In this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot Jupiter WASP-121b. We first refine the orbital properties of WASP-121b, which is on a nearly polar (obliquity psi(North) = 88.1 +/- 0.25 degrees or psi(South) = 91.11 +/- 0.20 degrees) orbit, and exclude a high differential rotation for its fast-rotating (P < 1.13 days), highly inclined (i(star)i star North = 8.1(-2.6)(+3.0)degrees-2.6+3.0 degrees or i(star)(South) i star South = 171.9(-3.4)(+2.5)degrees-3.4+2.5 degrees ) star. We then present a new method that exploits the reloaded Rossiter-McLaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord. Its application to HARPS transit spectroscopy of WASP-121b reveals the absorption signature from metals, likely atomic iron, in the planet atmospheric limb. The width of the signal (14.3 +/- 1.2 km s(-1)) can be explained by the rotation of the tidally locked planet. Its blueshift (-5.2 +/- 0.5 km s(-1)) could trace strong winds from the dayside to the nightside, or the anisotropic expansion of the planetary thermosphere.
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