We report the first discovery of a thick-disk planet, LHS 1815b (TOI-704b, TIC 260004324), detected in the TESS survey. LHS 1815b transits a bright (V = 12.19 mag, K = 7.99 mag) and quiet M dwarf located 29.87±0.02pc away with a mass of 0.502±0.015M⊙ and a radius of 0.501±0.030R⊙. We validate the planet by combining space and ground-based photometry, spectroscopy, and imaging. The planet has a radius of 1.088±0.064R⊕ with a 3σ mass upper-limit of 8.7M⊕. We analyze the galactic kinematics and orbit of the host star LHS1815 and find that it has a large probability (Pthick/Pthin=6482) to be in the thick disk with a much higher expected maximal height (Zmax=1.8kpc) above the Galactic plane compared with other TESS planet host stars. Future studies of the interior structure and atmospheric properties of planets in such systems using for example the upcoming James Webb Space Telescope (JWST), can investigate the differences in formation efficiency and evolution for planetary systems between different Galactic components (thick and thin disks, and halo).
@article{arxiv.2003.04525,
title = {LHS 1815b: The First Thick-Disk Planet Detected By TESS},
author = {Tianjun Gan and Avi Shporer and John H. Livingston and Karen A. Collins and Shude Mao and Alessandro A. Trani and Davide Gandolfi and Teruyuki Hirano and Rafael Luque and Keivan G. Stassun and Carl Ziegler and Steve B. Howell and Coel Hellier and Jonathan M. Irwin and Jennifer G. Winters and David R. Anderson and César Briceño and Nicholas Law and Andrew W. Mann and Xavier Bonfils and Nicola Astudillo-Defru and Eric L. N. Jensen and Guillem Anglada-Escudé and George R. Ricker and Roland Vanderspek and David W. Latham and Sara Seager and Joshua N. Winn and Jon M. Jenkins and Gabor Furesz and Natalia M. Guerrero and Elisa Quintana and Joseph D. Twicken and Douglas A. Caldwell and Peter Tenenbaum and Chelsea X. Huang and Pamela Rowden and Bárbara Rojas-Ayala},
journal= {arXiv preprint arXiv:2003.04525},
year = {2020}
}