WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star

L. Delrez, A. Santerne, J.-M. Almenara, D. R. Anderson, Andrew Collier Cameron, R. F. Díaz, M. Gillon, C. Hellier, E. Jehin, M. Lendl, P. F. L. Maxted, M. Neveu-VanMalle, F. Pepe, D. Pollacco, D. Queloz, D. Ségransan, B. Smalley, A. M. S. Smith, A. H. M. J. Triaud, S. UdryV. Van Grootel, R. G. West

Research output: Contribution to journalArticlepeer-review

118 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)4025-4043
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date7 Mar 2016
Publication statusPublished - 1 Jun 2016


  • Techniques: photometric
  • Techniques: radial velocities
  • Techniques: spectroscopic
  • Stars: individual: WASP-121
  • Planetary systems


Dive into the research topics of 'WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star'. Together they form a unique fingerprint.

Cite this