The discovery and mass measurement of a new ultra-short-period Planet: K2-131b

Fei Dai, Joshua N. Winn, Davide Gandolfi, Sharon X. Wang, Johanna K. Teske, Jennifer Burt, Simon Albrecht, Oscar Barragán, William D. Cochran, Michael Endl, Malcolm Fridlund, Artie P. Hatzes, Teruyuki Hirano, Lea A. Hirsch, Marshall C. Johnson, Anders Bo Justesen, John Livingston, Carina M. Persson, Jorge Prieto-Arranz, Andrew VanderburgRoi Alonso, Giuliano Antoniciello, Pamela Arriagada, R. P. Butler, Juan Cabrera, Jeffrey D. Crane, Felice Cusano, Szilárd Csizmadia, Hans Deeg, Sergio B. Dieterich, Philipp Eigmüller, Anders Erikson, Mark E. Everett, Akihiko Fukui, Sascha Grziwa, Eike W. Guenther, Gregory W. Henry, Steve B. Howell, John Asher Johnson, Judith Korth, Masayuki Kuzuhara, Norio Narita, David Nespral, Grzegorz Nowak, Enric Palle, Martin Pätzold, Heike Rauer, Pilar Montañés Rodríguez, Stephen A. Shectman, Alexis M.S. Smith, Ian B. Thompson, Vincent Van Eylen, Michael W. Williamson, Robert A. Wittenmyer

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


We report the discovery of a new ultra-short-period planet and summarize the properties of all such planets for which the mass and radius have been measured. The new planet, K2-131b, was discovered in K2 Campaign 10. It has a radius of and orbits a G dwarf with a period of 8.9 hr. Radial velocities obtained with Magellan/PFS and TNG/HARPS-N show evidence for stellar activity along with orbital motion. We determined the planetary mass using two different methods: (1) the "floating chunk offset" method, based only on changes in velocity observed on the same night; and (2) a Gaussian process regression based on both the radial velocity and photometric time series. The results are consistent and lead to a mass measurement of and a mean density of g cm-3.

Original languageEnglish (US)
Article number226
JournalAstronomical Journal
Issue number6
StatePublished - Dec 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • individual (EPIC 228732031)
  • planetary systems - stars


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