We report the discovery of GJ 1252 b, a planet with a radius of 1.193 ± 0.074 R⊕ and an orbital period of 0.52 days around an M3-type star (0.381 ± 0.019 M⊙, 0.391 ± 0.020 R⊙) located 20.385 ± 0.019 pc away. We use TESS data, ground-based photometry and spectroscopy, Gaia astrometry, and high angular resolution imaging to show that the transit signal seen in the TESS data must originate from a transiting planet. We do so by ruling out all false positive scenarios that attempt to explain the transit signal as originating from an eclipsing stellar binary. Precise Doppler monitoring also leads to a tentative mass measurement of 2.09 ± 0.56 M⊕. The host star proximity, brightness (V = 12.19 mag, K = 7.92 mag), low stellar activity, and the system's short orbital period make this planet an attractive target for detailed characterization, including precise mass measurement, looking for other objects in the system, and planet atmosphere characterization.
@article{arxiv.1912.05556,
title = {GJ 1252 b: A 1.2 $R_{\oplus}$ planet transiting an M3-dwarf at 20.4 pc},
author = {Avi Shporer and Karen A. Collins and Nicola Astudillo-Defru and Jonathan Irwin and Xavier Bonfils and Kevin I. Collins and Elisabeth Matthews and Jennifer G. Winters and David R. Anderson and James D. Armstrong and David Charbonneau and Ryan Cloutier and Tansu Daylan and Tianjun Gan and Maximilian N. Günther and Coel Hellier and Keith Horne and Chelsea X. Huang and Eric L. N. Jensen and John Kielkopf and Enric Palle and Ramotholo Sefako and Keivan G. Stassun and Thiam-Guan Tan and Andrew Vanderburg and George R. Ricker and David W. Latham and Roland Vanderspek and Sara Seager and Joshua N. Winn and Jon M. Jenkins and Knicole Colon and Courtney D. Dressing and Sébastien Lépine and Philip S. Muirhead and Mark E. Rose and Joseph D. Twicken and Jesus Noel Villasenor},
journal= {arXiv preprint arXiv:1912.05556},
year = {2020}
}