2015A&A...575A..61A

We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31M_Jup; 1.46R_Jup) in a 4.9-day, near-aligned (λ=12.7±4.2°) orbit around CD-24 102 (V=10.7; F9). Due to the low density of the planet and the apparent brightness of the host star, WASP-20 is a good target for atmospheric characterisation via transmission spectroscopy. WASP-28b is an inflated, Jupiter-mass planet (0.91M_Jup; 1.21R_Jup) in a 3.4-day, near-aligned (λ=8±18°) orbit around a V=12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7⁺²_–1Gyr and 6000±100K for WASP-20; 5⁺³_–2Gyr and 6100±150K for WASP-28), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars' spins via tidal dissipation.