Validation of a temperate fourth planet in the K2-133 multiplanet system

Abstract

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 starwith 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.

A possibly inflated planet around the bright young star DS Tucanae A

“…As a final step, we run the free and open source validation tool vespa (Morton 2012 to evaluate the false positive probability (FPP) of DS Tuc A b in a Bayesian framework. vespa has been widely used (e.g., Montet et al 2015;Crossfield et al 2016;Malavolta et al 2018;Mayo et al 2018;Wells et al 2019) to estimate the probability that a given signal is actually produced by a real planet and not the result of different astrophysical configurations. As reported in Morton (2012), the false positive scenarios explored by vespa are: i) a non-associated back/foreground eclipsing binary blended inside the photometric aperture of the target (BEB), ii) a hierarchical triple system where two components eclipse (HEB), iii) an eclipsing binary (EB), iv) a non-associated blended back/foreground star hosting a transiting planet (Bpl).…”