WASP-121 b : a hot Jupiter close to tidal disruption transiting an active F star
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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+0.064−0.062 MJup, a radius of 1.865 ± 0.044 RJup, and transits every 1.2749255+0.0000020−0.0000025 days an active F6-type main-sequence star (V = 10.4, 1.353+0.080−0.079 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∘.3−5∘.5. 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.
Delrez , L , Santerne , A , Almenara , J-M , Anderson , D R , Cameron , A C , Díaz , R F , Gillon , M , Hellier , C , Jehin , E , Lendl , M , 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 , V & West , R G 2016 , ' WASP-121 b : a hot Jupiter close to tidal disruption transiting an active F star ' Monthly Notices of the Royal Astronomical Society , vol 458 , no. 4 , pp. 4025-4043 . DOI: 10.1093/mnras/stw522
Monthly Notices of the Royal Astronomical Society
© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://dx.doi.org/10.1093/mnras/stw522
Funding for WASP comes from consortium universities and from UK’s Science and Technology Facilities Council. TRAPPIST is a project funded by the Belgian Fund for Scientific Research (Fonds National de la Recherche Scientifique, F.R.S.-FNRS) under grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Fundation (SNF). The Swiss Euler Telescope is operated by the University of Geneva, and is funded by the Swiss National Science Foundation. LD acknowledges support of the F.R.I.A. fund of the FNRS. MG, EJ and VVG are FNRS Research Associates. ML acknowledges support of the European Research Council through the European Union‘s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 336480. AHMJT received funding from a fellowship provided by the Swiss National Science Foundation under grant number P300P2-147773.ASis supported by the European Union under a Marie Curie Intra-European Fellowship for Career Development with reference FP7-PEOPLE- 2013-IEF, number 627202.