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, Ks = 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 (Rb = 1.40 ± 0.06 R⊕, Rc = 1.34 ± 0.08 R⊕), while the outer planet is a warm sub-Neptune (Rd = 2.6 ± 0.1 R⊕). We estimate the stellar age to be 360−140+490 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.
@article{arxiv.1803.05056,
title = {Three small planets transiting the bright young field star K2-233},
author = {Trevor J. David and Ian J. M. Crossfield and Björn Benneke and Erik A. Petigura and Erica J. Gonzales and Joshua E. Schlieder and Liang Yu and Howard T. Isaacson and Andrew W. Howard and David R. Ciardi and Eric E. Mamajek and Lynne A. Hillenbrand and Ann Marie Cody and Adric Riedel and Hans Martin Schwengeler and Christopher Tanner and Martin Ende},
journal= {arXiv preprint arXiv:1803.05056},
year = {2018}
}