WASP-31b: a low-density planet transiting a metal-poor, late-F-type dwarf star

D.~R. Anderson, A. Collier Cameron, C. Hellier, M. Lendl, T.~A. Lister, P.~F.~L. Maxted, D. Queloz, B. Smalley, A.~M.~S. Smith, A.~H.~M.~J. Triaud, R.~G. West, D.~J.~A. Brown, M. Gillon, F. Pepe, D. Pollacco, D. Ségransan, R.~A. Street, S. Udry