[en] We present the discovery by the WASP-South survey of WASP-121 b, a new remarkable short-period transiting hot Jupiter. The planet has a mass of 1.183_{-0.062}^{+0.064} MJup, a radius of 1.865 ± 0.044 RJup, and transits every 1.274 9255_{-0.000 0025}^{+0.000 0020} days an active F6-type main-sequence star (V = 10.4, 1.353_{-0.079}^{+0.080} M⊙, 1.458 ± 0.030 R⊙, Teff = 6460 ± 140 K). A notable property of WASP-121 b is that its orbital semimajor axis is only ˜1.15 times larger than its Roche limit, which suggests that the planet is close to tidal disruption. Furthermore, its large size and extreme irradiation (˜7.1 109 erg s-1 cm-2) make it an excellent target for atmospheric studies via secondary eclipse observations. Using the TRAnsiting Planets and PlanetesImals Small Telescope, we indeed detect its emission in the z'-band at better than ˜4σ, the measured occultation depth being 603 ± 130 ppm. Finally, from a measurement of the Rossiter-McLaughlin effect with the CORALIE spectrograph, we infer a sky-projected spin-orbit angle of 257.8°_{-5.5°}^{+5.3°}. This result may suggest a significant misalignment between the spin axis of the host star and the orbital plane of the planet. If confirmed, this high misalignment would favour a migration of the planet involving strong dynamical events with a third body.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Delrez, Laetitia ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Santerne, A.
Almenara, J.-M.
Anderson, D. R.
Collier-Cameron, A.
Diaz, R. F.
Gillon, Michaël ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Hellier, C.
Jehin, Emmanuel ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Lendl, Monika ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Maxted, P. F. L.
Neveu-VanMalle, M.
Pepe, F.
Pollacco, D.
Queloz, D.
Ségransan, D.
Smalley, B.
Smith, A. M. S.
Triaud, A. H. M. J.
Udry, S.
Van Grootel, Valérie ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
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