WASP-20b and WASP-28b: a hot Saturn and a hot Jupiter in near-aligned orbits around solar-type stars

Hellier; Smalley; Maxted

Abstract

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 (0.31?MJup; 1.46?RJup) in a 4.9-day, near-aligned (? = 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 (0.91?MJup; 1.21?RJup) in a 3.4-day, near-aligned (? = 8 ± 18°) orbit around a V = 12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7+ 2-1 Gyr and 6000 ± 100 K for WASP-20; 5+ 3-2 Gyr and 6100 ± 150 K 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.

Citation

Hellier, Smalley, & Maxted. (2015). WASP-20b and WASP-28b: a hot Saturn and a hot Jupiter in near-aligned orbits around solar-type stars. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/201423591

• Acceptance Date: Dec 5, 2014
• Publication Date: Feb 24, 2015
• Journal: Astronomy & Astrophysics
• Print ISSN: 0004-6361
• Publisher: EDP Sciences
• DOI: https://doi.org/10.1051/0004-6361/201423591
• Keywords: planetary systems, stars, WASP-20b, WASP-28b
• Publisher URL: https://doi.org/10.1051/0004-6361/201423591