TOI-222: a single-transit TESS candidate revealed to be a 34-d eclipsing binary with CORALIE, EulerCam, and NGTS

We report the period, eccentricity, and mass determination for the TESS single-transit event candidate TOI-222, which displayed a single 3000 ppm transit in the TESS two-minute cadence data from Sector 2. We determine the orbital period via radial velocity measurements (P = 33.9 days), which allowed for ground-based photometric detection of two subsequent transits. Our data show that the companion to TOI-222is a low mass star, with a radius of 0.27 R_sun and a mass of 0.23 M_sun. This makes TOI-222 one of the longest period low-mass eclipsing binary systems to be characterised with accurate radii and masses. It also showcases the ability to efficiently discover systems from TESS single transit events using a combination of radial velocity monitoring coupled with high precision ground-based photometry.

[1]  Jason D. Eastman,et al.  Minerva-Australis. I. Design, Commissioning, and First Photometric Results , 2019, Publications of the Astronomical Society of the Pacific.

[2]  L. Hillenbrand,et al.  New Low-mass Eclipsing Binary Systems in Praesepe Discovered by K2 , 2017, 1706.03084.

[3]  Keivan G. Stassun,et al.  Empirical Accurate Masses and Radii of Single Stars with TESS and Gaia , 2017, 1710.01460.

[4]  Howard Isaacson,et al.  Kepler Planet-Detection Mission: Introduction and First Results , 2010, Science.

[5]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[6]  Keivan G. Stassun,et al.  HD 202772A b: A Transiting Hot Jupiter around a Bright, Mildly Evolved Star in a Visual Binary Discovered by TESS , 2018, The Astronomical Journal.

[8]  A. Gimenez,et al.  Accurate masses and radii of normal stars: modern results and applications , 2009, 0908.2624.

[9]  D. Monet,et al.  THE FOURTH US NAVAL OBSERVATORY CCD ASTROGRAPH CATALOG (UCAC4) , 2012, 1212.6182.

[10]  梅畑 豪紀,et al.  39th COSPAR Scientific Assembly , 2012 .

[11]  Gilles Chabrier,et al.  Evolution of low-mass star and brown dwarf eclipsing binaries , 2007, 0707.1792.

[12]  J. Hagelberg,et al.  Signs of strong Na and K absorption in the transmission spectrum of WASP-103b , 2017, 1708.05737.

[13]  R. G. West,et al.  WASP-42 b and WASP-49 b: two new transiting sub-Jupiters , 2012, 1205.2757.

[14]  B. Scott Gaudi,et al.  An Estimate of the Yield of Single-transit Planetary Events from the Transiting Exoplanet Survey Satellite , 2018, The Astronomical Journal.

[15]  Daniel Foreman-Mackey,et al.  Fast and Scalable Gaussian Process Modeling with Applications to Astronomical Time Series , 2017, 1703.09710.

[16]  Don Pollacco,et al.  Single site observations of TESS single transit detections , 2018, Astronomy & Astrophysics.

[17]  D. Gough,et al.  The influence of a magnetic field on Schwarzschild's criterion for convective instability in an ideally conducting fluid , 1966 .

[18]  F. Bouchy,et al.  The EBLM project , 2019, Astronomy & Astrophysics.

[19]  K. Stassun,et al.  Evidence for a Systematic Offset of −80 μas in the Gaia DR2 Parallaxes , 2018, The Astrophysical Journal.

[20]  K. Stassun,et al.  EVIDENCE FOR A SYSTEMATIC OFFSET OF −0.25 mas IN THE GAIA DR1 PARALLAXES , 2016, 1609.05390.

[21]  T. Henning,et al.  HD 1397b: A Transiting Warm Giant Planet Orbiting A V = 7.8 mag Subgiant Star Discovered by TESS , 2018, The Astronomical Journal.

[22]  Mark Clampin,et al.  Transiting Exoplanet Survey Satellite , 2014, 1406.0151.

[23]  A. Jord'an,et al.  Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters , 2015, 1503.07020.

[24]  Observatoire de la Côte d'Azur,et al.  Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties , 2016, 1609.04172.

[25]  Laura Kreidberg,et al.  batman: BAsic Transit Model cAlculatioN in Python , 2015, 1507.08285.

[26]  F. Faedi,et al.  Single transit candidates from K2: detection and period estimation , 2015, 1512.03722.

[27]  D. Ciardi,et al.  Understanding Super-Earths with MINERVA-Australis at USQ's Mount Kent Observatory , 2018, 1806.09282.

[28]  Nate B. Lust,et al.  ON CORRELATED-NOISE ANALYSES APPLIED TO EXOPLANET LIGHT CURVES , 2016, 1610.01336.

[29]  Cyril Cavadore,et al.  HARPS: ESO's coming planet searcher. Chasing exoplanets with the La Silla 3.6-m telescope , 2002 .

[30]  D. Rubin,et al.  Inference from Iterative Simulation Using Multiple Sequences , 1992 .

[31]  K. Stassun,et al.  Accurate Empirical Radii and Masses of Planets and Their Host Stars with Gaia Parallaxes , 2016, 1609.04389.

[32]  F. Pepe,et al.  A Jovian planet in an eccentric 11.5 day orbit around HD 1397 discovered by TESS , 2018, Astronomy & Astrophysics.

[33]  L. Fossati,et al.  TESS’s first planet , 2018, Astronomy & Astrophysics.

[34]  C. Bailer-Jones,et al.  Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2 , 2018, The Astronomical Journal.

[35]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[36]  Chelsea X. Huang,et al.  TESS Discovery of a Transiting Super-Earth in the pi Mensae System , 2018, The astrophysical journal. Letters.

[37]  J. Southworth.  Homogeneous studies of transiting extrasolar planets - II. Physical properties , 2008, 0811.3277.

[38]  K. Braun,et al.  HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS , 2015, 1501.01635.

[39]  A. Tokovinin.  Ten Years of Speckle Interferometry at SOAR , 2018, 1801.04772.

[40]  P. G. Jonker,et al.  American Astronomical Society Meeting Abstracts , 2011 .

[41]  Edward Gillen,et al.  The Next Generation Transit Survey (NGTS) , 2018 .

[42]  Rafael Brahm,et al.  CERES: A Set of Automated Routines for Echelle Spectra , 2016, 1609.02279.

[43]  P. Cargile,et al.  THE SOLAR NEIGHBORHOOD. XXXVII. THE MASS–LUMINOSITY RELATION FOR MAIN-SEQUENCE M DWARFS , 2016, 1608.04775.

[44]  Martin C. Stumpe,et al.  Multiscale Systematic Error Correction via Wavelet-Based Bandsplitting in Kepler Data , 2014 .

[45]  Martin C. Stumpe,et al.  Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction , 2012, 1203.1383.

[46]  David Charbonneau,et al.  The transit light curve project. I. Four consecutive transits of the exoplanet XO-1b , 2006 .

[47]  Molefe Mokoene,et al.  The Messenger , 1995, Outrageous Fortune.

[48]  L. Buchhave,et al.  KIC 1571511B: a benchmark low-mass star in an eclipsing binary system in the Kepler field , 2011, 1111.2578.

[49]  Martin G. Cohen,et al.  THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE): MISSION DESCRIPTION AND INITIAL ON-ORBIT PERFORMANCE , 2010, 1008.0031.

[50]  C. Soubiran,et al.  Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec , 2014, 1407.2608.

[51]  P. Maxted,et al.  The atmospheric parameters of FGK stars using wavelet analysis of CORALIE spectra , 2018, 1801.06106.

[52]  R. Paul Butler,et al.  THE HARPS-TERRA PROJECT. I. DESCRIPTION OF THE ALGORITHMS, PERFORMANCE, AND NEW MEASUREMENTS ON A FEW REMARKABLE STARS OBSERVED BY HARPS , 2012, 1202.2570.

[53]  A. Collier Cameron,et al.  The thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 μm , 2009, 0911.5087.

[54]  Tsevi Mazeh,et al.  Correcting systematic effects in a large set of photometric light curves , 2005, astro-ph/0502056.