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

Creators: Dragomir, Diana; Ciardi, David R.; Fulton, Benjamin J.

Abstract

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^(+0.17)_(-0.16) R⊕, and combined archival and follow-up precision radial velocity data put the mass of the planet at 22.7^(+2.2)_(-1.9) M⊕. 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 (R_p = 0.892^(+0.064)_(-0.058)R⊕) planet from TESS. The HD 21749 system is a prime target for comparative studies of planetary composition and architecture in multi-planet systems.

Additional Information

© 2019 The American Astronomical Society. Received 2018 December 31; revised 2019 March 8; accepted 2019 March 16; published 2019 April 15. We thank the referee for a careful report on the manuscript. The implementation of their suggestions has significantly improved the clarity of the Letter. Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This Letter includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). This Letter is based in part on observations collected at the European Southern Observatory under ESO programs 076.C-0762(A), 096.C-0499(A), 183.C-0972(A), and 072.C-0488(E). This work makes use of observations from the LCOGT network. D.D. and J.T. acknowledge support for this work provided by NASA through Hubble Fellowship grants HST-HF2-51372.001-A and HST-HF2-51399.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. M.N.G., J.B., and C.X.H. acknowledge support from MITs Kavli Institute as Torres postdoctoral fellows. A.V.'s work was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. J.E.R. was supported by the Harvard Future Faculty Leaders Postdoctoral fellowship. X.D. acknowledges support from the Branco Weiss Fellowship-Society in Science. Software: EXOFASTv2 (Eastman 2017), allesfitter (M. Güenther & T. Daylan 2019, in preparation), celerite (Foreman-Mackey et al. 2017), ellc (Maxted 2016), dynesty (https://github.com/joshspeagle/dynesty), emcee (Foreman-Mackey et al. 2013), celerite (Foreman-Mackey et al. 2017), RadVel (Fulton et al. 2018), SpecMatch (Petigura et al. 2017). Facilities: TESS - , ESO 3.6 m: HARPS - , Magellan Clay: Planet Finder Spectrograph - , VLT: NACO - , KELT - , LCO: NRES - , Euler 1.2 m: CORALIE. -

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