TY  - JOUR
A1  - Wells, Robert
A1  - Poppenhäger, Katja
A1  - Watson, C. A.
T1  - Validation of a temperate fourth planet in the K2-133 multiplanet system
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present follow-up observations of the K2-133 multiplanet 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 star's 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.
KW  - techniques: photometric
KW  - planets and satellites: general
KW  - stars: individual: LP 358-499
KW  - stars: individual: K2-133
KW  - stars: low-mass
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz1334
SN  - 0035-8711
SN  - 1365-2966
VL  - 487
IS  - 2
SP  - 1865
EP  - 1873
PB  - Oxford Univ. Press
CY  - Oxford
ER  -