WASP-21b: a hot-Saturn exoplanet transiting a thick disc star

F. Bouchy; L. Hebb; I. Skillen; A. Collier Cameron; B. Smalley; S. Udry; D. R. Anderson; I. Boisse; B. Enoch; C. A. Haswell; G. Hébrard; C. Hellier; Y. Joshi; S. R. Kane; P. F. L. Maxted; M. Mayor; C. Moutou; F. Pepe; D. Pollacco; D. Queloz; D. Ségransan; E. K. Simpson; A. M. S. Smith; H. C. Stempels; R. Street; A. H. M. J. Triaud; R. G. West; P. J. Wheatley

doi:10.1051/0004-6361/201014817

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arXiv · 1006.2605

WASP-21b: a hot-Saturn exoplanet transiting a thick disc star

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Abstract

We report the discovery of WASP-21b, a new transiting exoplanet discovered by the Wide Angle Search for Planets (WASP) Consortium and established and characterized with the FIES, SOPHIE, CORALIE and HARPS fiber-fed echelle spectrographs. A 4.3-d period, 1.1% transit depth and 3.4-h duration are derived for WASP-21b using SuperWASP-North and high precision photometric observations at the Liverpool Telescope. Simultaneous fitting to the photometric and radial velocity data with a Markov Chain Monte Carlo procedure leads to a planet in the mass regime of Saturn. With a radius of 1.07 R_Jup and mass of 0.30 M_Jup, WASP-21b has a density close to 0.24 rho_Jup corresponding to the distribution peak at low density of transiting gaseous giant planets. With a host star metallicity [Fe/H] of -0.46, WASP-21b strengthens the correlation between planetary density and host star metallicity for the five known Saturn-like transiting planets. Furthermore there are clear indications that WASP-21b is the first transiting planet belonging to the thick disc.

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F. Bouchy, L. Hebb, I. Skillen, A. Collier Cameron, B. Smalley, S. Udry, D. R. Anderson, I. Boisse, B. Enoch, C. A. Haswell, G. Hébrard, C. Hellier, Y. Joshi, S. R. Kane, P. F. L. Maxted, M. Mayor, C. Moutou, F. Pepe, D. Pollacco, D. Queloz, D. Ségransan, E. K. Simpson, A. M. S. Smith, H. C. Stempels, R. Street, A. H. M. J. Triaud, R. G. West, P. J. Wheatley. 2010-06-14. WASP-21b: a hot-Saturn exoplanet transiting a thick disc star. https://doi.org/10.1051/0004-6361%2F201014817

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