A Jovian planet in an eccentric 11.5 day orbit around HD 1397 discovered by TESS

¹ Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland
e-mail: Louise.Nielsen@unige.ch
² Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
³ Department of Earth Sciences, University of California, Riverside, CA 92521, USA
⁴ University of Southern Queensland, Centre for Astrophysics, Toowoomba, QLD 4530, Australia
⁵ SETI Institute, Mountain View, CA 94043, USA
⁶ Proto-Logic LLC, Washington, DC 20009, USA
⁷ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁸ Department of Physics and Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139, USA
⁹ Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, PA 18015, USA
¹⁰ Leidos/NASA Ames Research Center, Moffett Field, CA 94035, USA
¹¹ Department of Physics & Astronomy, Vanderbilt University, 6301 Stevenson Center Ln., Nashville, TN 37235, USA
¹² Department of Earth, Atmospheric, and Planetary Sciences, and Department of Aeronautics and Astronautics, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
¹³ Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
¹⁴ NASA Ames Research Center, Moffett Field, CA 94035, USA
¹⁵ Caltech/IPAC-NASA Exoplanet Science Institute, M/S 100-22, 770 S. Wilson Ave, Pasadena, CA 91106, USA
¹⁶ UC Santa Cruz, Department of Astronomy & Astrophysics, 1156 High Street, Santa Cruz, CA 95064, USA
¹⁷ NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20771, USA
¹⁸ Department of Astronomy, The University of Texas at Austin, 2515 Speedway C1400, Austin, TX 78712, USA
¹⁹ Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
²⁰ Astronomy Department, University of Florida, 211 Bryant Space Science Center, PO Box 112055, Gainesville, FL 32611-2055, USA
²¹ Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, USA
²² Exoplanetary Science at UNSW, School of Physics, UNSW Sydney, NSW 2052, Australia
²³ School of Astronomy and Space Science, Key Laboratory of Ministry of Education, Nanjing University, Nanjing, PR China

Received: 5 November 2018
Accepted: 18 February 2019

Abstract

The Transiting Exoplanet Survey Satellite TESS has begun a new age of exoplanet discoveries around bright host stars. We present the discovery of HD 1397b (TOI-120.01), a giant planet in an 11.54-day eccentric orbit around a bright (V = 7.9) G-type subgiant. We estimate both host star and planetary parameters consistently using EXOFASTv2 based on TESS time-series photometry of transits and radial velocity measurements with CORALIE and MINERVA-Australis. We also present high angular resolution imaging with NaCo to rule out any nearby eclipsing binaries. We find that HD 1397b is a Jovian planet, with a mass of 0.415 ± 0.020 M_J and a radius of 1.026 ± 0.026 R_J. Characterising giant planets in short-period eccentric orbits, such as HD 1397b, is important for understanding and testing theories for the formation and migration of giant planets as well as planet-star interactions.