The future of exoplanet science is bright, as TESS once again demonstrates with the discovery of its longest-period confirmed planet to date. We hereby present HD 21749b (TOI 186.01), a sub-Neptune in a 36-day orbit around a bright (V = 8.1) nearby (16 pc) K4.5 dwarf. TESS measures HD21749b to be 2.61−0.16+0.17R⊕, and combined archival and follow-up precision radial velocity data put the mass of the planet at 22.7−1.9+2.2M⊕. HD 21749b contributes to the TESS Level 1 Science Requirement of providing 50 transiting planets smaller than 4 R⊕ with measured masses. Furthermore, we report the discovery of HD 21749c (TOI 186.02), the first Earth-sized (Rp=0.892−0.058+0.064R⊕) planet from TESS. The HD21749 system is a prime target for comparative studies of planetary composition and architecture in multi-planet systems.
@article{arxiv.1901.00051,
title = {TESS delivers its first Earth-sized planet and a warm sub-Neptune},
author = {Diana Dragomir and Johanna Teske and Maximilian N. Gunther and Damien Ségransan and Jennifer A. Burt and Chelsea X. Huang and Andrew Vanderburg and Elisabeth Matthews and Xavier Dumusque and Keivan G. Stassun and Joshua Pepper and George R. Ricker and Roland Vanderspek and David W. Latham and Sara Seager and Joshua N. Winn and Jon M. Jenkins and Thomas Beatty and François Bouchy and Timothy M. Brown and R. Paul Butler and David R. Ciardi and Jeffrey D. Crane and Jason D. Eastman and Luca Fossati and Jim Francis and Benjamin J. Fulton and B. Scott Gaudi and Robert F. Goeke and David James and Todd C. Klaus and Rudolf B. Kuhn and Christophe Lovis and Michael B. Lund and Scott McDermott and Martin Paegert and Francesco Pepe and Joseph E. Rodriguez and Lizhou Sha and Stephen A. Shectman and Avi Shporer and Robert J. Siverd and Aylin Garcia Soto and Daniel J. Stevens and Joseph D. Twicken and Stéphane Udry and Steven Villanueva and Sharon X. Wang and Bill Wohler and Xinyu Yao and Zhuchang Zhan},
journal= {arXiv preprint arXiv:1901.00051},
year = {2019}
}