TESS Delivers Its First Earth-sized Planet and a Warm Sub-Neptune

Dragomir, Diana; Teske, Johanna; Gunther, Maximilian N.; Segransan, Damien; Burt, Jennifer A.; Huang, Chelsea X.; Vanderburg, Andrew; Matthews, Elisabeth; Dumusque, Xavier; Stassun, Keivan G.; Pepper, Joshua; Ricker, Eorge R.; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Beatty, Thomas; Bouchy, Rancois; Brown, Timothy M.; Butler, R. Paul; Ciardi, Avid R.; Crane, Jeffrey D.; Eastman, Jason D.; Fossati, Luca; Francis, Jim; Fulton, Benjamin J.; Gaudi, B. Scott; Goeke, Robert F.; James, David; Klaus, Todd C.; Kuhn, Rudolf B.; Lovis, Christophe; Lund, Michael B.; McDermott, Scott; Paegert, Martin; Pepe, Francesco; Rodriguez, Joseph E.; Sha, Lizhou; Shectman, Stephen A.; Shporer, Avi; Siverd, Robert J.; Soto, Aylin Garcia; Stevens, Daniel J.; Twicken, Joseph D.; Udry, Stephane; Villanueva, Steven, Jr.; Wang, Sharon X.; Wohler, Bill; Yao, Xinyu; Zhan, Zhuchang
2019
ASTROPHYSICAL JOURNAL LETTERS
DOI
10.3847/2041-8213/ab12ed
The future of exoplanet science is bright, as Transiting Exoplanet Survey Satellite (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 HD 21749b to be 2.61(-0.16)(+0.17)R(circle plus), and combined archival and follow-up precision radial velocity data put the mass of the planet at 22.7(-1.9)(+2.2)M(circle plus). HD 21749b contributes to the TESS Level 1 Science Requirement of providing 50 transiting planets smaller than 4 R-circle plus with measured masses. Furthermore, we report the discovery of HD 21749c (TOI 186.02), the first Earth-sized (R-p = 0.8921(-0.058)(+0.064)R(circle plus)) planet from TESS. The HD 21749 system is a prime target for comparative studies of planetary composition and architecture in multi-planet systems.