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

Teruyuki Hirano, Fei Dai, John H. Livingston, Yuka Fujii, William D. Cochran, Michael Endl, Davide Gandolfi, Seth Redfield, Joshua N. Winn, Eike W. Guenther, Jorge Prieto-Arranz, Simon Albrecht, Oscar Barragan, Juan Cabrera, P. Wilson Cauley, Szilard Csizmadia, Hans Deeg, Philipp Eigmüller, Anders Erikson, Malcolm FridlundAkihiko Fukui, Sascha Grziwa, Artie P. Hatzes, Judith Korth, Norio Narita, David Nespral, Prajwal Niraula, Grzegorz Nowak, Martin Pätzold, Enric Palle, Carina M. Persson, Heike Rauer, Ignasi Ribas, Alexis M.S. Smith, Vincent Van Eylen

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


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+0.20R and 6.34365 ±0.00028 days for the inner planet; 1.95-0.22+0.27R and 13.85402 ±0.00088 days for the middle planet; and 1.64-0.17+0.18 R 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 ∼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 (US)
Article number124
JournalAstronomical Journal
Issue number3
StatePublished - Mar 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planets and satellites: detection
  • stars: individual (K2-155 = EPIC 210897587)
  • techniques: photometric
  • techniques: radial velocities
  • techniques: spectroscopic


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