K2-155: A Bright Metal-poor M Dwarf with Three Transiting Super-Earths

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    Teruyuki Hirano, Tokyo Inst Technol, Tokyo Institute of Technology, Dept Earth & Planetary Sci, Meguro Ku, Fei Dai, Princeton Univ, Princeton University, Dept Astrophys Sci, John H. Livingston, Univ Tokyo, University of Tokyo, Grad Sch Sci, Dept Astron, Bunkyo Ku, Yuka Fujii, Tokyo Inst Technol, Earth Life Sci Inst, William D. Cochran, Univ Texas Austin, University of Texas Austin, McDonald Observ, Michael Endl, Univ Texas Austin, University of Texas Austin, McDonald Observ, Davide Gandolfi, Univ Torino, University of Turin, Dipartimento Fis, Seth Redfield, Wesleyan Univ, Van Vleck Observ, Joshua N. Winn, Princeton Univ, Princeton University, Dept Astrophys Sci, Eike W. Guenther, Thuringer Landessternwarte Tautenburg TLS, Jorge Prieto-Arranz, Univ Laguna ULL, Dept Astrofis,
  • Simon Albrecht
  • Oscar Barragan, Univ Torino, University of Turin, Dipartimento Fis, Juan Cabrera, German Aerosp Ctr, Inst Planetary Res, P. Wilson Cauley, Arizona State Univ, Sch Earth & Space Explorat, Szilard Csizmadia, German Aerosp Ctr, Inst Planetary Res, Hans Deeg, Univ Laguna ULL, Dept Astrofis, Philipp Eigmueller, German Aerosp Ctr, Inst Planetary Res, Anders Erikson, German Aerosp Ctr, Inst Planetary Res, Malcolm Fridlund, Chalmers Univ Technol, Onsala Space Observ, Dept Space Earth & Environm, Akihiko Fukui, Natl Astron Observ Japan, National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS) - Japan, Okayama Astrophys Observ, Sascha Grziwa, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch, Artie P. Hatzes, Thuringer Landessternwarte Tautenburg TLS, Judith Korth, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch, Norio Narita, Natl Astron Observ Japan, National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS) - Japan, Okayama Astrophys Observ, David Nespral, Univ Laguna ULL, Dept Astrofis, Prajwal Niraula, Wesleyan Univ, Van Vleck Observ, Grzegorz Nowak, Univ Laguna ULL, Dept Astrofis, Martin Paetzold, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch, Enric Palle, Univ Laguna ULL, Dept Astrofis, Carina M. Persson, Chalmers Univ Technol, Onsala Space Observ, Dept Space Earth & Environm, Heike Rauer, TU Berlin, Technical University of Berlin, Ctr Astron & Astrophys, Ignasi Ribas, Fac Ciencies, University of Barcelona, Inst Ciencies Espai CSIC IEEC, Alexis M. S. Smith, German Aerosp Ctr, Inst Planetary Res, Vincent Van Eylen, Leiden Univ, Leiden University, Leiden Observ

We report on the discovery of three transiting super-Earths around K2-155 (EPIC 210897587), a relatively bright early M dwarf (V = 12.81 mag) observed during Campaign 13 of the NASA K2 mission. To characterize the system and validate the planet candidates, we conducted speckle imaging and high-dispersion optical spectroscopy, including radial velocity measurements. Based on the K2 light curve and the spectroscopic characterization of the host star, the planet sizes and orbital periods are 1.55(-0.17)(+0.20) R-circle plus and 6.34365 +/- 0.00028 days for the inner planet; 1.95(-0.22)(+0.27) R-circle plus and 13.85402 +/- 0.00088 days for the middle planet; and 1.64(-0.17)(+0.18) R-circle plus and 40.6835 +/- 0.0031 days for the outer planet. The outer planet (K2-155d) is near the habitable zone, with an insolation 1.67 +/- 0.38 times that of the Earth. The planet's radius falls within the range between that of smaller rocky planets and larger gas-rich planets. To assess the habitability of this planet, we present a series of three-dimensional global climate simulations, assuming that K2-155d is tidally locked and has an Earth-like composition and atmosphere. We find that the planet can maintain a moderate surface temperature if the insolation proves to be smaller than similar to 1.5 times that of the Earth. Doppler mass measurements, transit spectroscopy, and other follow-up observations should be rewarding, as K2-155 is one of the optically brightest M dwarfs known to harbor transiting planets.

Original languageEnglish
Article number124
JournalAstronomical Journal
Volume155
Issue number3
Number of pages11
ISSN0004-6256
DOIs
StatePublished - Mar 2018

    Research areas

  • planets and satellites: detection, stars: individual (K2-155=EPIC 210897587), techniques: photometric, techniques: radial velocities, techniques: spectroscopic, PHOTOMETRIC SYSTEMS, ASIAGO DATABASE, OPEN CLUSTERS, MISSION, PLANET, STARS, RICH, SIGNATURES, TELESCOPE, ADPS

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