We report the discovery from K2 of a transiting terrestrial planet in an ultra-short-period orbit around an M3-dwarf. K2-137 b completes an orbit in only 4.3 hours, the second-shortest orbital period of any known planet, just 4 minutes longer than that of KOI 1843.03, which also orbits an M-dwarf. Using a combination of archival images, AO imaging, RV measurements, and light curve modelling, we show that no plausible eclipsing binary scenario can explain the K2 light curve, and thus confirm the planetary nature of the system. The planet, whose radius we determine to be 0.89 +/- 0.09 Earth radii, and which must have a iron mass fraction greater than 0.45, orbits a star of mass 0.463 +/- 0.052 Msol and radius 0.442 +/- 0.044 Rsol.
@article{arxiv.1707.04549,
title = {K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf},
author = {A. M. S. Smith and J. Cabrera and Sz. Csizmadia and F. Dai and D. Gandolfi and T. Hirano and J. N. Winn and S. Albrecht and R. Alonso and G. Antoniciello and O. Barragán and H. Deeg and Ph. Eigmüller and M. Endl and A. Erikson and M. Fridlund and A. Fukui and S. Grziwa and E. W. Guenther and A. P. Hatzes and D. Hidalgo and A. W. Howard and H. Isaacson and J. Korth and M. Kuzuhara and J. Livingston and N. Narita and D. Nespral and G. Nowak and E. Palle and M. Pätzold and C. M. Persson and E. Petigura and J. Prieto-Arranz and H. Rauer and I. Ribas and V. Van Eylen},
journal= {arXiv preprint arXiv:1707.04549},
year = {2018}
}
Comments
12 pages, 9 figures, accepted for publication in MNRAS