Validation of a Temperate Fourth Planet in the K2-133 Multi-planet System

We present follow-up observations of the K2-133 multi-planet system. Previously, we announced that K2-133 contained three super-Earths orbiting an M1.5V host star – with tentative evidence of a fourth outer-planet orbiting at the edge of the temperate zone.

Here we report on the validation of the presence of the fourth planet, determining a radius of 1.73+0.14−0.13 R⊕. The four planets span the radius gap of the exoplanet population, meaning further follow-up would be worthwhile to obtain masses and test theories of the origin of the gap. In particular, the trend of increasing planetary radius with decreasing incident flux in the K2-133 system supports the claim that the gap is caused by photo-evaporation of exoplanet atmospheres. Finally, we note that K2-133 e orbits on the edge of the stars temperate zone, and that our radius measurement allows for the possibility that this is a rocky world. Additional mass measurements are required to confirm or refute this scenario.

R. Wells, K. Poppenhaeger, C. A. Watson
(Submitted on 13 May 2019)
Comments: Accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1905.05206 [astro-ph.EP] (or arXiv:1905.05206v1 [astro-ph.EP] for this version)
Submission history
From: Robert Wells
[v1] Mon, 13 May 2019 18:00:08 UTC (1,821 KB)
https://arxiv.org/abs/1905.05206
Astrobiology