A 38 Million Year Old Neptune-sized Planet in the Kepler Field

Creators: Bouma, L. G.; Curtis, J. L.; Masuda, K.; Hillenbrand, L. A.; Stefánsson, G.; Isaacson, H.; Narita, N.; Fukui, A.; Ikoma, M.; Tamura, M.; Kraus, A. L.; Furlan, E.; Gnilka, C. L.; Lester, K. V.; Howell, S. B.

Abstract

Kepler 1627A is a G8V star previously known to host a 3.8 R⊕ planet on a 7.2 day orbit. The star was observed by the Kepler space telescope because it is nearby (d = 329 pc) and it resembles the Sun. Here, we show using Gaia kinematics, TESS stellar rotation periods, and spectroscopic lithium abundances that Kepler 1627 is a member of the 38⁺⁶₋₅ Myr old δ Lyr cluster. To our knowledge, this makes Kepler 1627Ab the youngest planet with a precise age yet found by the prime Kepler mission. The Kepler photometry shows two peculiarities: the average transit profile is asymmetric, and the individual transit times might be correlated with the local light-curve slope. We discuss possible explanations for each anomaly. More importantly, the δ Lyr cluster is one of ∼10³ coeval groups whose properties have been clarified by Gaia. Many other exoplanet hosts are candidate members of these clusters; their ages can be verified with the trifecta of Gaia, TESS, and ground-based spectroscopy.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 October 12; revised 2021 December 6; accepted 2021 December 27; published 2022 February 9. The authors are grateful to J. Winn, J. Spake, A. Howard, and T. David for illuminating discussions and suggestions, and to R. Kerr for providing us with the Kerr et al. (2021) membership list prior to its publication. The authors are also grateful to K. Collins for helping resolve the scheduling conflict that would have otherwise prevented the MuSCAT3 observations. L.G.B. acknowledges support from a Charlotte Elizabeth Procter Fellowship from Princeton University, as well as from the TESS GI Program (NASA grant 80NSSC21K0335) and the Heising-Simons Foundation (51 Pegasi b Fellowship). Keck/NIRC2 imaging was acquired by program 2015A/N301N2L (PI: A. Kraus). In addition, this paper is based in part on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center and under financial support by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory. This work is partly supported by JSPS KAKENHI Grant Nos. 22000005, JP15H02063, JP17H04574, JP18H05439, and JP18H05442, JST PRESTO grant No. JPMJPR1775, and the Astrobiology Center of National Institutes of Natural Sciences (NINS; grant No. AB031010). This paper also includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission directorate. We thank the TESS Architects (G. Ricker, R. Vanderspek, D. Latham, S. Seager, and J. Jenkins) and the many TESS team members for their efforts to make the mission a continued success. Finally, this research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. We also thank the Keck Observatory staff for their support of HIRES and remote observing. We recognize the importance that the summit of Maunakea has within the indigenous Hawaiian community, and are deeply grateful to have the opportunity to conduct observations from this mountain. Software: altaipony (Ilin et al. 2021), astrobase (Bhatti et al. 2018), astropy (Astropy Collaboration et al. 2018), astroquery (Ginsburg et al. 2018), corner (Foreman-Mackey 2016), exoplanet (Foreman-Mackey et al. 2021), and its dependencies Agol et al. (2020); Kipping (2013); Luger et al. (2019); Theano Development Team (2016), PyMC3 (Salvatier et al. 2016), scipy (Jones et al. 2001), TESS-point (Burke et al. 2020), wotan (Hippke et al. 2019). Facility: Astrometry: Gaia (Gaia Collaboration et al. 2018b; Gaia Collaboration 2021a). Imaging: Second Generation Digitized Sky Survey. Keck:II (NIRC2; www2.keck.hawaii.edu/inst/nirc2). Gemini:North ('Alopeke; Scott et al. (2018, 2021). Spectroscopy: Keck:I (HIRES; Vogt et al. 1994). Photometry: Kepler (Borucki et al. 2010), MuSCAT3 (Narita et al. 2020), TESS (Ricker et al. 2015).

Attached Files

Published - Bouma_2022_AJ_163_121.pdf

Accepted Version - 2112.14776.pdf

Files

2112.14776.pdf

Files (10.7 MB)

Name	Size	Download all
2112.14776.pdf md5:8b22defe78a40b1a1c00cbcfb3dc3e71	6.6 MB	Preview Download
Bouma_2022_AJ_163_121.pdf md5:29ee6ac9de4cb3076c298cb3f07d0da2	4.1 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes