Zodiacal exoplanets in time (ZEIT) - II. A `super-Earth' orbiting a young K dwarf in the Pleiades Neighbourhood
Abstract
We describe a `super-Earth'-size (2.30 ± 0.16 R⊕) planet transiting an early K-type dwarf star in the Campaign 4 field observed by the K2 mission. The host star, EPIC 210363145, was identified as a candidate member of the approximately 120 Myr-old Pleiades cluster based on its kinematics and photometric distance. It is rotationally variable and exhibits near-ultraviolet emission consistent with a Pleiades age, but its rotational period is ≈20 d and its spectrum contains no Hα emission nor the Li I absorption expected of Pleiades K dwarfs. Instead, the star is probably an interloper that is unaffiliated with the cluster, but younger (≲1.3 Gyr) than the typical field dwarf. We ruled out a false positive transit signal produced by confusion with a background eclipsing binary by adaptive optics imaging and a statistical calculation. Doppler radial velocity measurements limit the companion mass to <2 times that of Jupiter. Screening of the light curves of 1014 potential Pleiades candidate stars uncovered no additional planets. An injection-and-recovery experiment using the K2 Pleiades light curves with simulated planets, assuming a planet population like that in the Kepler prime field, predicts only 0.8-1.8 detections (versus ∼20 in an equivalent Kepler sample). The absence of Pleiades planet detections can be attributed to the much shorter monitoring time of K2 (80 d versus 4 yr), increased measurement noise due to spacecraft motion, and the intrinsic noisiness of the stars.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2017
- DOI:
- 10.1093/mnras/stw2345
- arXiv:
- arXiv:1606.05812
- Bibcode:
- 2017MNRAS.464..850G
- Keywords:
-
- planets and satellites: general;
- stars: low-mass;
- planetary systems;
- open clusters and associations: individual: Pleiades;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- submitted to MNRAS, comments welcome