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Identifying Young Kepler Planet Host Stars from Keck–HIRES Spectra of Lithium

Berger, Travis A. and Howard, Andrew W. and Boesgaard, Ann Merchant (2018) Identifying Young Kepler Planet Host Stars from Keck–HIRES Spectra of Lithium. Astrophysical Journal, 855 (2). Art. No. 115. ISSN 1538-4357.

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The lithium doublet at 6708 Å provides an age diagnostic for main sequence FGK dwarfs. We measured the abundance of lithium in 1305 stars with detected transiting planets from the Kepler mission using high-resolution spectroscopy. Our catalog of lithium measurements from this sample has a range of abundance from A(Li) = 3.11 ± 0.07 to an upper limit of −0.84 dex. For a magnitude-limited sample that comprises 960 of the 1305 stars, our Keck–HIRES spectra have a median signal-to-noise ratio of 45 per pixel at ~6700 Å with spectral resolution λ/(Δλ) = R = 55,000. We identify 80 young stars that have A(Li) values greater than the Hyades at their respective effective temperatures; these stars are younger than ~650 Myr, the approximate age of the Hyades. We then compare the distribution of A(Li) with planet size, multiplicity, orbital period, and insolation flux. We find larger planets preferentially in younger systems, with an A–D two-sided test p-value = 0.002, a > 3σ confidence that the older and younger planet samples do not come from the same parent distribution. This is consistent with planet inflation/photoevaporation at early ages. The other planet parameters (Kepler planet multiplicity, orbital period, and insolation flux) are uncorrelated with age.

Item Type:Article
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URLURL TypeDescription Paper
Berger, Travis A.0000-0002-2580-3614
Howard, Andrew W.0000-0001-8638-0320
Boesgaard, Ann Merchant0000-0002-8468-9532
Additional Information:© 2018. The American Astronomical Society. Received 2017 September 29; revised 2018 January 19; accepted 2018 February 19; published 2018 March 14. T.A.B. thanks Daniel Huber, Sam Grunblatt, Conor McPartland, Benjamin Boe, Christian Flores, Maissa Salama, and Zhoujian Zhang for useful discussion regarding the pipeline and statistical tests. T.A.B. also thanks Michael Lum for his model atmosphere interpolation code and guidance with MOOG and Christopher Waters for his assistance with equivalent width fitting packages. A.W.H. acknowledges NASA grant NNX12AJ23G. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. The authors thank Joshua Winn, Benjamin Fulton, David Soderblom, and Howard Isaacson for feedback and discussion on previous drafts of this paper. The authors also thank the many observers who helped gather these spectra. Additionally, the authors thank the reviewer for the useful comments on the submitted drafts of this paper. 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 authors thank the time allocation committees of the University of Hawaii, the University of California, and the California Institute of Technology for large allocations of telescope time. Finally, the authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Software: MOOG (Sneden et al. 2012), LMFIT (Newville et al. 2014), PyRAF (Science Software Branch at STScI 2012), SciPy (Jones et al. 2001), Pandas (McKinney 2010), Matplotlib (Hunter 2007).
Group:Astronomy Department
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:planetary systems; stars: abundances
Issue or Number:2
Record Number:CaltechAUTHORS:20180328-133307509
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Official Citation:Travis A. Berger et al 2018 ApJ 855 115
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85479
Deposited By: George Porter
Deposited On:28 Mar 2018 22:00
Last Modified:03 Oct 2019 19:31

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