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Eleven Multiplanet Systems from K2 Campaigns 1 and 2 and the Masses of Two Hot Super-Earths

Sinukoff, Evan and Howard, Andrew W. and Petigura, Erik A. and Schlieder, Joshua E. and Crossfield, Ian J. M. and Ciardi, David R. and Fulton, Benjamin J. and Isaacson, Howard and Aller, Kimberly M. and Baranec, Christoph and Beichman, Charles A. and Hansen, Brad M. S. and Knutson, Heather A. and Law, Nicholas M. and Liu, Michael C. and Riddle, Reed and Dressing, Courtney D. (2016) Eleven Multiplanet Systems from K2 Campaigns 1 and 2 and the Masses of Two Hot Super-Earths. Astrophysical Journal, 827 (1). Art. No. 78. ISSN 0004-637X.

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We present a catalog of 11 multiplanet systems from Campaigns 1 and 2 of the K2 mission. We report the sizes and orbits of 26 planets split between seven two-planet systems and four three-planet systems. These planets stem from a systematic search of the K2 photometry for all dwarf stars observed by K2 in these fields. We precisely characterized the host stars with adaptive optics imaging and analysis of high-resolution optical spectra from Keck/HIRES and medium-resolution spectra from IRTF/SpeX. We confirm two planet candidates by mass detection and validate the remaining 24 candidates to >99% confidence. Thirteen planets were previously validated or confirmed by other studies, and 24 were previously identified as planet candidates. The planets are mostly smaller than Neptune (21/26 planets), as in the Kepler mission, and all have short periods (P < 50 days) due to the duration of the K2 photometry. The host stars are relatively bright (most have Kp < 12.5 mag) and are amenable to follow-up characterization. For K2-38, we measured precise radial velocities using Keck/HIRES and provide initial estimates of the planet masses. K2-38b is a short-period super-Earth with a radius of 1.55 ± 0.16 R⊕, a mass of 12.0 ± 2.9 M⊕, and a high density consistent with an iron-rich composition. The outer planet K2-38c is a lower-density sub-Neptune-size planet with a radius of 2.42 ± 0.29 R⊕ and a mass of 9.9 ± 4.6 M⊕ that likely has a substantial envelope. This new planet sample demonstrates the capability of K2 to discover numerous planetary systems around bright stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sinukoff, Evan0000-0002-5658-0601
Howard, Andrew W.0000-0001-8638-0320
Petigura, Erik A.0000-0003-0967-2893
Ciardi, David R.0000-0002-5741-3047
Fulton, Benjamin J.0000-0003-3504-5316
Isaacson, Howard0000-0002-0531-1073
Baranec, Christoph0000-0002-1917-9157
Knutson, Heather A.0000-0002-0822-3095
Law, Nicholas M.0000-0001-9380-6457
Liu, Michael C.0000-0003-2232-7664
Riddle, Reed0000-0002-0387-370X
Dressing, Courtney D.0000-0001-8189-0233
Additional Information:© 2016 The American Astronomical Society. Received 2015 November 28; revised 2016 May 10; accepted 2016 May 17; published 2016 August 9. We thank Sam Grunblatt, Matthew Hosek Jr., John Livingston, and Geoff Marcy for helpful discussions. We thank Lauren Weiss and Lea Hirsch for their help with observing with Keck-HIRES. E.S. is supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). E.A.P. acknowledges support from a Hubble Fellowship grant HST-HF2-51365.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. A.W.H. acknowledges support for our K2 team through a NASA Astrophysics Data Analysis Program grant. A.W.H. and I.J.M.C. acknowledge support from the K2 Guest Observer Program. E.D.L. received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 313014 (ETAEARTH). The research of J.E.S. was supported by an appointment to the NASA Postdoctoral Program at NASA Ames Research Center, administered by Oak Ridge Associated Universities through a contract with NASA. B.J.F. acknowledges support from a National Science Foundation Graduate Research Fellowship under grant no. 2014184874. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract no. DE-AC02-05CH11231. This work made use of the SIMBAD database (operated at CDS, Strasbourg, France), NASA's Astrophysics Data System Bibliographic Services, and data products from the Two Micron All Sky Survey (2MASS), the APASS database, the SDSS-III project, and the Digitized Sky Survey. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). 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. This research was made possible through the use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund. This study benefits from use of the Robo-AO system, which was developed by collaborating partner institutions, the California Institute of Technology, and the Inter-University Centre for Astronomy and Astrophysics, and with the support of the National Science Foundation under grant nos. AST-0906060, AST-0960343, and AST-1207891, the Mt. Cuba Astronomical Foundation, and by a gift from Samuel Oschin. Ongoing science operation support of Robo-AO is provided by the California Institute of Technology and the University of Hawai'i. C.B. acknowledges support from the Alfred P. Sloan Foundation. Some of the data presented herein were obtained at the W. M. Keck Observatory (which is operated as a scientific partnership among Caltech, UC, and NASA). The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Kepler - The Kepler Mission, K2 - , Keck:I (HIRES) - KECK I Telescope, Keck:II (NIRC2) - KECK II Telescope, IRTF (Spex) - Infrared Telescope Facility, Palomar:Hale (PALM-3000/PHARO) - , PO:1.5 m (Robo-AO) - .
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
NASA Hubble FellowshipHST-HF2-51365.001-A
NASANAS 5-26555
K2 Guest Observer ProgramUNSPECIFIED
European Research Council (ERC)313014 (ETAEARTH)
NASA Postdoctoral ProgramUNSPECIFIED
NSF Graduate Research Fellowship2014184874
Department of Energy (DOE)DE-AC02-05CH11231
Robert Martin Ayers Sciences FundUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
University of Hawai‘iUNSPECIFIED
Subject Keywords:planetary systems – stars: late-type – stars: solar-type – techniques: photometric – techniques: radial velocities – techniques: spectroscopic
Record Number:CaltechAUTHORS:20160810-152533844
Persistent URL:
Official Citation:Evan Sinukoff et al 2016 ApJ 827 78
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69553
Deposited By: Tony Diaz
Deposited On:10 Aug 2016 23:02
Last Modified:19 Oct 2017 22:21

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