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K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf

Smith, A. M. S. and Howard, A. W. and Petigura, E. (2018) K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf. Monthly Notices of the Royal Astronomical Society, 474 (4). pp. 5523-5533. ISSN 0035-8711.

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We report the discovery in K2's Campaign 10 of a transiting terrestrial planet in an ultra-short-period orbit around an M3-dwarf. K2-137 b completes an orbit in only 4.3 h, the second shortest orbital period of any known planet, just 4 min longer than that of KOI 1843.03, which also orbits an M-dwarf. Using a combination of archival images, adaptive optics imaging, radial velocity measurements, and light-curve modelling, we show that no plausible eclipsing binary scenario can explain the K2 light curve, and thus confirm the planetary nature of the system. The planet, whose radius we determine to be 0.89 ± 0.09 R⊕, and which must have an iron mass fraction greater than 0.45, orbits a star of mass 0.463 ± 0.052 M⊙ and radius 0.442 ± 0.044 R⊙.

Item Type:Article
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URLURL TypeDescription Paper
Howard, A. W.0000-0001-8638-0320
Petigura, E.0000-0003-0967-2893
Additional Information:© 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 November 3. Received 2017 November 2; in original form 2017 July 14. Published: 08 November 2017. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. We greatly thank the NOT staff members for their precious support during the observations. Based on observations obtained with the NOT, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofísica de Andalucia under a joint agreement with the University of Copenhagen and NOTSA. DG gratefully acknowledges the financial support of the Programma Giovani Ricercatori – Rita Levi Montalcini – Rientro dei Cervelli (2012) awarded by the Italian Ministry of Education, Universities and Research. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The WIYN/NESSI observations were conducted as part of an approved NOAO observing program (PI: Livingston, proposal ID 2017A-0377). Data presented herein were obtained at the WIYN Observatory from telescope time allocated to NN-EXPLORE through the scientific partnership of the National Aeronautics and Space Administration, the National Science Foundation, and the National Optical Astronomy Observatory. This work was supported by a NASA WIYN PI Data Award, administered by the NASA Exoplanet Science Institute. NESSI was funded by the NASA Exoplanet Exploration Program and the NASA Ames Research Center. NESSI was built at the Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. This research has made use of NASA's Astrophysics Data System, the SIMBAD data base, operated at CDS, Strasbourg, France, the Exoplanet Orbit Database and the Exoplanet Data Explorer at, and the Exoplanets Encyclopaedia at We also used Astropy, a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013), and the DASCH project at Harvard, which is partially supported by NSF grants AST-0407380, AST-0909073, and AST-1313370. The Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under grant no. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under grant no. AST-1238877, the University of Maryland, and Eotvos Lorand University. The Digitized Sky Surveys were produced at the STScI under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. The National Geographic Society – Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. SzCs acknowledges support from the Hungarian OTKA Grant K113117. Finally, we wish to thank the anonymous referee whose comments helped to improve the manuscript.
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR)UNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
University of HawaiiUNSPECIFIED
Max Planck Institute for Astronomy (MPIA)UNSPECIFIED
Max Planck Institute for Extraterrestrial PhysicsUNSPECIFIED
Johns Hopkins UniversityUNSPECIFIED
Durham UniversityUNSPECIFIED
University of EdinburghUNSPECIFIED
Queen's University BelfastUNSPECIFIED
Harvard-Smithsonian Center for AstrophysicsUNSPECIFIED
Las Cumbres Observatory Global Telescope NetworkUNSPECIFIED
National Central University of TaiwanUNSPECIFIED
Space Telescope Science InstituteUNSPECIFIED
University of MarylandUNSPECIFIED
Eotvos Lorand University (ELTE)UNSPECIFIED
National Geographic SocietyUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Samuel Oschin FoundationUNSPECIFIED
Eastman Kodak CompanyUNSPECIFIED
Hungarian Scientific Research Fund (OTKA)K113117
Subject Keywords:planets and satellites: detection, planets and satellites: individual: K2-137 b
Issue or Number:4
Record Number:CaltechAUTHORS:20180103-165734518
Persistent URL:
Official Citation:A M S Smith, J Cabrera, Sz Csizmadia, F Dai, D Gandolfi, T Hirano, J N Winn, S Albrecht, R Alonso, G Antoniciello, O Barragán, H Deeg, Ph Eigmüller, M Endl, A Erikson, M Fridlund, A Fukui, S Grziwa, E W Guenther, A P Hatzes, D Hidalgo, A W Howard, H Isaacson, J Korth, M Kuzuhara, J Livingston, N Narita, D Nespral, G Nowak, E Palle, M Pätzold, C M Persson, E Petigura, J Prieto-Arranz, H Rauer, I Ribas, V Van Eylen; K2-137 b: an Earth-sized planet in a 4.3-h orbit around an M-dwarf, Monthly Notices of the Royal Astronomical Society, Volume 474, Issue 4, 11 March 2018, Pages 5523–5533,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84077
Deposited By: Melissa Ray
Deposited On:05 Jan 2018 18:23
Last Modified:03 Oct 2019 19:14

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