WASP-50 b: a hot Jupiter transiting a moderately active solar-type star

M. Gillon, A.~P. Doyle, M. Lendl, P.~F.~L. Maxted, A.~H.~M.~J. Triaud, D.~R. Anderson, S.~C.~C. Barros, J. Bento, A. Collier-Cameron, B. Enoch, F. Faedi, C. Hellier, E. Jehin, P. Magain, J. Montalbán, F. Pepe, D. Pollacco, D. Queloz, B. Smalley, D. SegransanA.~M.~S. Smith, J. Southworth, S. Udry, R.~G. West, P.~J. Wheatley

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29 Citations (Scopus)


We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.0295 plusmn 0.0009 AU) around a moderately bright (V = 11.6, K = 10) G9 dwarf (0.89 plusmn 0.08 M$_⊙$, 0.84 plusmn 0.03 R$_⊙$) in the Southern constellation Eridanus. Thanks to high-precision follow-up photometry and spectroscopy obtained by the telescopes TRAPPIST and Euler, the mass and size of this planet, WASP-50 b, are well constrained to 1.47 plusmn 0.09 M$_Jup$ and 1.15 plusmn 0.05 R$_Jup$, respectively. The transit ephemeris is 2 455 558.6120 (plusmn0.0002) + N times 1.955096 (plusmn0.000005) HJD$_UTC$. The size of the planet is consistent with basic models of irradiated giant planets. The chromospheric activity (log R'$_HK = -4.67$) and rotational period (P$_rot$ = 16.3 plusmn 0.5 days) of the host star suggest an age of 0.8 plusmn 0.4 Gy that is discrepant with a stellar-evolution estimate based on the measured stellar parameters ($$_∗$ = 1.48 plusmn 0.10 $$_⊙$, T$_eff$ = 5400 plusmn 100 K, [Fe/H] = -0.12 plusmn 0.08) which favors an age of 7 plusmn 3.5 Gy. This discrepancy could be explained by the tidal and magnetic influence of the planet on the star, in good agreement with the observations that stars hosting hot Jupiters tend to show faster rotation and magnetic activity. We measure a stellar inclination of 84$_-31+6$ deg, disfavoring a high stellar obliquity. Thanks to its large irradiation and the relatively small size of its host star, WASP-50 b is a good target for occultation spectrophotometry, making it able to constrain the relationship between hot Jupiters' atmospheric thermal profiles and the chromospheric activity of their host stars. The photometric time-series used in this work are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr ( or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A88
Original languageEnglish
Pages (from-to)A88
JournalAstronomy and Astrophysics
Publication statusPublished - 1 Sept 2011


  • techniques: spectroscopic, planetary systems, techniques: radial velocities, stars: individual: WASP-50, techniques: photometric


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