Sixty Validated Planets from K2 Campaigns 5–8

Creators: Livingston, John H.; Crossfield, Ian J. M.; Petigura, Erik A.; Gonzales, Erica J.; Ciardi, David R.; Beichman, Charles A.; Christiansen, Jessie L.; Dressing, Courtney D.; Henning, Thomas; Howard, Andrew W.; Isaacson, Howard; Fulton, Benjamin J.; Kosiarek, Molly; Schlieder, Joshua E.; Sinukoff, Evan; Tamura, Motohide

Abstract

We present a uniform analysis of 155 candidates from the second year of NASA's K2 mission (Campaigns 5–8), yielding 60 statistically validated planets spanning a range of properties with median values of R_p = 2.5 R⊕, P = 7.1 days, T_(eq) = 811 K, and J = 11.3 mag. The sample includes 24 planets in 11 multiplanetary systems, as well as 18 false positives and 77 remaining planet candidates. Of particular interest are 18 planets smaller than 2 R⊕, five orbiting stars brighter than J = 10 mag, and a system of four small planets orbiting the solar-type star EPIC 212157262. We compute planetary transit parameters and false-positive probabilities using a robust statistical framework and present a complete analysis incorporating the results of an intensive campaign of high-resolution imaging and spectroscopic observations. This work brings the K2 yield to over 360 planets, and by extrapolation, we expect that K2 will have discovered ~600 planets before the expected depletion of its onboard fuel in late 2018.

Additional Information

© 2018 The American Astronomical Society. Received 2018 May 23; revised 2018 October 1; accepted 2018 October 6; published 2018 November 26. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the National Aeronautics and Space Administration (NASA) Science Mission directorate. This work benefited from the Exoplanet Summer Program in the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, a program funded by the Heising-Simons Foundation. Portions of this work were performed under contract with the Jet Propulsion Laboratory (JPL), funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. This research has made use of the NASA Exoplanet Archive, which is operated by Caltech, under contract with NASA's Exoplanet Exploration Program. This work made use of the SIMBAD database (operated at CDS, Strasbourg, France) and NASA's Astrophysics Data System Bibliographic Services. This research made use of the Infrared Science Archive, which is operated by the California Institute of Technology (Caltech), under contract with NASA. Portions of this work were performed at Caltech under contract with NASA. JHL gratefully acknowledges the support of the Japan Society for the Promotion of Science (JSPS) Research Fellowship for Young Scientists. ES is supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada. EAP acknowledges support by NASA through a Hubble Fellowship grant 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. BJF was supported by the National Science Foundation Graduate Research Fellowship under grant No. 2014184874. AWH acknowledges support for our K2 team through a NASA Astrophysics Data Analysis Program grant. AWH and IJMC acknowledge support from the K2 Guest Observer Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership between Caltech, the University of California, and NASA. The authors wish to extend special thanks to those of Hawai'ian ancestry, on whose sacred mountain of Maunakea we are privileged to be guests. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Kepler - The Kepler Mission, Gaia - , Keck (NIRC2 - , HIRES) - , Gemini (DSSI - , NIRI) - , Palomar (PHARO - , TripleSpec) - , WIYN (NESSI) - , NTT (SOFI) - , IRTF (SpeX). - Software: numpy (Oliphant 2006), scipy (Jones et al. 2001), matplotlib (Hunter 2007), lmfit (Newville et al. 2014), emcee (Foreman-Mackey et al. 2013), batman (Kreidberg 2015), isochrones (Morton 2015a), vespa (Morton 2015b).

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