Discovery of a Transiting Adolescent Sub-Neptune Exoplanet with K2

Creators: David, Trevor J.; Mamajek, Eric E.; Vanderburg, Andrew; Schlieder, Joshua E.; Bristow, Makennah; Petigura, Erik A.; Ciardi, David R.; Crossfield, Ian J. M.; Isaacson, Howard T.; Cody, Ann Marie; Stauffer, John R.; Hillenbrand, Lynne A.; Bieryla, Allyson; Latham, David W.; Fulton, Benjamin J.; Rebull, Luisa M.; Beichman, Chas; Gonzales, Erica J.; Hirsch, Lea A.; Howard, Andrew W.; Vasisht, Gautam; Ygouf, Marie

Abstract

The role of stellar age in the measured properties and occurrence rates of exoplanets is not well understood. This is in part due to a paucity of known young planets and the uncertainties in age-dating for most exoplanet host stars. Exoplanets with well-constrained ages, particularly those which are young, are useful as benchmarks for studies aiming to constrain the evolutionary timescales relevant for planets. Such timescales may concern orbital migration, gravitational contraction, or atmospheric photoevaporation, among other mechanisms. Here we report the discovery of an adolescent transiting sub-Neptune from K2 photometry of the low-mass star EPIC 247267267. From multiple age indicators, we estimate the age of the star to be 120 Myr, with a 68% confidence interval of 100–760 Myr. The size of EPIC 247267267 b (R P = 2.8 ± 0.1 R⊕) combined with its youth make it an intriguing case study for photoevaporation models, which predict enhanced atmospheric mass loss during early evolutionary stages.

Additional Information

© 2018 The American Astronomical Society. Received 2018 January 19; revised 2018 October 27; accepted 2018 November 4; published 2018 December 6. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We thank the anonymous referee for comments which improved this manuscript. T.J.D. and E.E.M. acknowledge support from the Jet Propulsion Laboratory Exoplanetary Science Initiative. M.B. acknowledges support from the North Carolina Space Grant Consortium. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. 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. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership of 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 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. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by 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, the 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 grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. 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. Facilities: FLWO:1.5 m (TRES) - , Keck:I (HIRES) - KECK I Telescope, Keck:II (NIRC2) - KECK II Telescope, Kepler - The Kepler Mission, PS1 - Panoramic Survey Telescope and Rapid Response System Telescope #1 (Pan-STARRS), Shane (ShARCS) - Lick Observatory's 3m Shane Telescope. Software: emcee (Foreman-Mackey et al. 2013), forecaster (Chen & Kipping 2017b), isoclassify (Huber et al. 2017), k2sc (Aigrain et al. 2016), k2sff (Vanderburg & Johnson 2014), pytransit (Parviainen 2015), radvel (Fulton et al. 2018), vespa (Morton 2015).

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