Description
We report the discovery by the WASP transit survey of a highly-irradiated, massive (2.242+/-0.080M_Jup_) planet which transits a bright (V=10.6), evolved F8 star every 2.9-days. The planet, WASP-71b, is larger than Jupiter (1.46+/-0.13R_Jup_), but less dense (0.71+/-0.16{rho}_Jup_). We also report spectroscopic observations made during transit with the CORALIE spectrograph, which allow us to make a highly-significant detection of the Rossiter-McLaughlin effect. We determine the sky-projected angle between the stellar-spin and planetary-orbit axes to be {lambda}=20.1+/-9.7degrees, i.e. the system is "aligned", according to the widely-used alignment criteria that systems are regarded as misaligned only when {lambda} is measured to be greater than 10 degrees with 3-{sigma} confidence.
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