WASP-128b : a transiting brown dwarf in the dynamical-tide regime
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Massive companions in close orbits around G dwarfs are thought to undergo rapid orbital decay due to runaway tidal dissipation. We report here the discovery of WASP-128b, a brown dwarf discovered by the WASP survey transiting a G0V host on a 2.2 d orbit, where the measured stellar rotation rate places the companion in a regime where tidal interaction is dominated by dynamical tides. Under the assumption of dynamical equilibrium, we derive a value of the stellar tidal quality factor logQ′⋆=6.96 ± 0.19. A combined analysis of ground-based photometry and high-resolution spectroscopy reveals a mass and radius of the host, M⋆ = 1.16 ± 0.04 M⊙, R⋆ = 1.16 ± 0.02 R⊙, and for the companion, Mb = 37.5 ± 0.8Mj, Rb = 0.94 ± 0.02Rj, placing WASP-128b in the driest parts of the brown dwarf desert, and suggesting a mild inflation for its age. We estimate a remaining lifetime for WASP-128b similar to that of some ultra-short period massive hot Jupiters, and note it may be a propitious candidate for measuring orbital decay and testing tidal theories.
Hodžić , V , Triaud , A H M J , Anderson , D R , Bouchy , F , Cameron , A C , Delrez , L , Gillon , M , Hellier , C , Jehin , E , Lendl , M , Maxted , P F L , Pepe , F , Pollacco , D , Queloz , D , Ségransan , D , Smalley , B , Udry , S & West , R 2018 , ' WASP-128b : a transiting brown dwarf in the dynamical-tide regime ' , Monthly Notices of the Royal Astronomical Society , vol. 481 , no. 4 , pp. 5091–5097 . https://doi.org/10.1093/mnras/sty2512
Monthly Notices of the Royal Astronomical Society
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1093/mnras/sty2512