TOI-222: a single-transit TESS candidate revealed to be a 34-d eclipsing binary with CORALIE, EulerCam, and NGTS
Henning, Thomas; Latham, David W.; Jordán, Andrés; Espinoza, Néstor; Brahm, Rafael; Wheatley, Peter J.; Bayliss, Daniel; Wittenmyer, Robert A.; Moyano, Maximiliano; Ziegler, Carl; Vanderspek, Roland; Seager, Sara; Jenkins, Jon M.; Caldwell, Douglas A.; Günther, Maximilian N.; Eigmüller, Philipp; Casewell, Sarah L.; Gill, Samuel; Goad, Michael R.; Anderson, David R.; Armstrong, David J.; Burleigh, Matthew R.; Gillen, Edward; Jenkins, James S.; Lendl, Monika; McCormac, James; Udry, Stéphane; Vines, Jose I.; West, Richard G.; Mann, Andrew W.; Rodriguez, Joseph E.; Twicken, Joseph D.; Bryant, Edward M.; Schlieder, Joshua; Bouchy, François; Chaushev, Alexander; Louden, Tom; Nielsen, Louise D.; Raynard, Liam; Sarkis, Paula; Stassun, Keivan; Ricker, George; Krishnamurthy, Akshata; Doty, John; Okumura, Jack; Wright, Duncan J.; Law, Nicholas; Briceño, César; Pollacco, Don; Morris, Robert; Acton, Jack S.; Tilbrook, Rosanna H.; Villanueva, Steven; Turner, Oliver; Cooke, Benjamin F.; Addison, Brett; Belardi, Claudia; Marmier, Maxime; Hagelberg, Janis; Winn, Josh; Goeke, Bob
Switzerland, Austria, United Kingdom, United States, Germany, Chile, Australia, Canada
Abstract
We report the period, eccentricity, and mass determination for the Transiting Exoplanet Survey Satellite (TESS) single-transit event candidate TOI-222, which displayed a single 3000 ppm transit in the TESS 2-min cadence data from Sector 2. We determine the orbital period via radial velocity measurements (P = 33.9 d), which allowed for ground-based photometric detection of two subsequent transits. Our data show that the companion to TOI-222 is a low-mass star, with a radius of 0.18_{-0.10}^{+0.39} R⊙ and a mass of 0.23 ± 0.01 M⊙. This discovery showcases the ability to efficiently discover long-period systems from TESS single-transit events using a combination of radial velocity monitoring coupled with high-precision ground-based photometry.