Three small planets transiting the bright young field star K2-233
astro-ph.EP
/ Authors
Trevor J. David, Ian J. M. Crossfield, Björn Benneke, Erik A. Petigura, Erica J. Gonzales, Joshua E. Schlieder, Liang Yu, Howard T. Isaacson, Andrew W. Howard, David R. Ciardi
and 7 more authors
Eric E. Mamajek, Lynne A. Hillenbrand, Ann Marie Cody, Adric Riedel, Hans Martin Schwengeler, Christopher Tanner, Martin Ende
/ Abstract
We report the detection of three small transiting planets around the young K3 dwarf K2-233 (2MASS J15215519-2013539) from observations during Campaign 15 of the K2 mission. The star is relatively nearby ($d$ = 69 pc) and bright ($V$ = 10.7 mag, $K_s$ = 8.4 mag), making the planetary system an attractive target for radial velocity follow-up and atmospheric characterization with the James Webb Space Telescope. The inner two planets are hot super-Earths ($R_b$ = 1.40 $\pm$ 0.06 R$_\oplus$, $R_c$ = 1.34 $\pm$ 0.08 R$_\oplus$), while the outer planet is a warm sub-Neptune ($R_d$ = 2.6 $\pm$ 0.1 R$_\oplus$). We estimate the stellar age to be 360$^{+490}_{-140}$ Myr based on rotation, activity, and kinematic indicators. The K2-233 system is particularly interesting given recent evidence for inflated radii in planets around similarly-aged stars, a trend potentially related to photo-evaporation, core-cooling, or both mechanisms.