By analyzing K2 short-cadence observations, we detect starspots on WASP-85A, the host star of the hot Jupiter WASP-85Ab. The detection of recurring starspot occultation events indicates that the planet’s orbit is aligned with the star’s rotational axis (λ \lt 14^\circ ) and suggests a stellar rotational period of 15.1 ± 0.6 days. The K2 light curve reveals a rotational modulation with a period of 13.6 ± 1.6 days, which is consistent with the period determined from starspots. There are no significant transit-timing variations, and thus no evidence of any additional planet in the system. Given the pronounced rotational modulation, we are only able to place an upper limit of 100 parts per million for any phase-curve modulations and the secondary eclipse.
The Astronomical Journal
- Pub Date:
- June 2016
- planets and satellites: individual: WASP-85Ab;
- stars: individual: WASP-85A;
- Astrophysics - Earth and Planetary Astrophysics
- 8 pages, 7 figures, 2 tables. Accepted for publication in The Astronomical Journal