Evidence of a Sub-Saturn around EPIC 211945201
Abstract
We report here strong evidence for a sub-Saturn around EPIC 211945201 and confirm its planetary nature. EPIC 211945201b was found to be a planetary candidate from K2 photometry in Campaigns 5 and 16, transiting a bright star (V mag = 10.15, G0 spectral type) in a 19.492 day orbit. However, the photometric data combined with false positive probability calculations using VESPA was not sufficient to confirm the planetary scenario. Here, we present high-resolution spectroscopic follow up of the target using the PARAS spectrograph (19 radial velocity observations) over a time baseline of 420 days. We conclusively rule out the possibility of an eclipsing binary system and confirm the 2σ detection of a sub-Saturn planet. The confirmed planet has a radius of 6.12 ± 0.1 R ⊕, and a mass of {27}-12.6+14 {M}\oplus . We also place an upper limit on the mass (within the 3σ confidence interval) at 42 M ⊕ above the nominal value. This results in the Saturn-like density of {0.65}-0.30+0.34 {{g}} {cm}}-3. Based on the mass and radius, we provide a preliminary model-dependent estimate that the heavy element content is 60%-70% of the total mass. This detection is important as it adds to a sparse catalog of confirmed exoplanets with masses between 10 and 70 M ⊕ and radii between 4 and 8 R ⊕, whose masses and radii are measured to a precision of 50% or better (only 23 including this work).
- Publication:
-
The Astronomical Journal
- Pub Date:
- July 2018
- DOI:
- 10.3847/1538-3881/aac436
- arXiv:
- arXiv:1805.03466
- Bibcode:
- 2018AJ....156....3C
- Keywords:
-
- planetary systems;
- stars: individual: EPIC 211945201;
- techniques: photometric;
- techniques: radial velocities;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication in The Astronomical Journal, 17 pages, 8 figures