Ages of Stars and Planets in the Kepler Field Younger than Four Billion Years
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1.
California Institute of Technology
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2.
Carnegie Observatories
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3.
University of California, Berkeley
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4.
Osaka University
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5.
Carnegie Mellon University
Abstract
Recent analyses of FGK stars in open clusters have helped clarify the precision with which a star's rotation rate and lithium content can be used as empirical indicators for its age. Here we apply this knowledge to stars observed by Kepler. Rotation periods are drawn from previous work; lithium is measured from new and archival Keck/HIRES spectra. We report rotation-based ages for 23,813 stars (harboring 795 known planets) for which our method is applicable. We find that our rotational ages recover the ages of stars in open clusters spanning 0.04–2.5 Gyr; they also agree with ≳90% of the independent lithium ages. The resulting yield includes 63 planets younger than 1 Gyr at 2σ, and 109 with median ages below 1 Gyr. This is about half the number expected under the classic assumption of a uniform star formation history. The age distribution that we observe, rather than being uniform, shows that the youngest stars in the Kepler field are 3–5 times rarer than stars 3 Gyr old. This trend holds for both known planet hosts and for the parent stellar sample. We attribute this "demographic cliff" to a combination of kinematic heating and a declining star formation rate in the Galaxy's thin disk, and highlight its impact on the age distribution of known transiting exoplanets.
Copyright and License
© 2024. 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.
Acknowledgement
We thank Kevin Schlaufman and the reviewer for suggestions that significantly improved the manuscript. This work was supported by the Heising-Simons 51 Pegasi b Fellowship (L.G.B. and E.K.P.), the Carnegie Institution for Science's Carnegie Fellowship (L.G.B.), and the Arthur R. Adams SURF Fellowship (E.K.P.). The HIRES data were obtained at the Keck Observatory. We recognize the importance and reverence that the summit of Maunakea has always held within the indigenous Hawaiian community, and we are deeply grateful for the opportunity to conduct observations from this mountain.
Funding
This work was supported by the Heising-Simons 51 Pegasi b Fellowship (L.G.B. and E.K.P.), the Carnegie Institution for Science's Carnegie Fellowship (L.G.B.), and the Arthur R. Adams SURF Fellowship (E.K.P.).
Contributions
Per https://credit.niso.org/: Conceptualization: L.G.B. Data curation: L.G.B., A.W.H., H.I. Formal analysis: L.G.B., K.M. Funding acquisition: L.G.B. Investigation: L.G.B., E.K.P. Methodology: L.G.B., E.K.P., K.M. Project administration: L.G.B., L.A.H., A.W.H. Resources: L.G.B., A.W.H. Software: L.G.B. Supervision: L.G.B., L.A.H. Validation: L.G.B., K.M. Visualization: L.G.B. Writing-original draft: L.G.B. Writing-review and editing: all authors.
Facilities
Gaia - (Gaia Collaboration et al. 2023), Kepler - The Kepler Mission (W. J. Borucki et al. 2010), Keck:I - KECK I Telescope (HIRES) (S. S. Vogt et al. 1994), CTIO:2MASS, FLWO:2MASS - (M. F. Skrutskie et al. 2006), Sloan - Sloan Digital Sky Survey Telescope (D. G. York et al. 2000).
Software References
astropy (Astropy Collaboration et al. 2013,2018, 2022), claude (https://claude.ai/), eagles (R. D. Jeffries et al. 2023), gyro-interp (L. G. Bouma et al. 2023; V0.6 available at doi:10.5281/zenodo.13733242), matplotlib (J. D. Hunter 2007), numpy (S. van Der Walt et al. 2011), scipy (P. Virtanen et al. 2020).
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Additional details
- Heising-Simons Foundation
- 51 Pegasi b Fellowship
- Carnegie Institution for Science
- Carnegie Fellowship
- California Institute of Technology
- Arthur R. Adams SURF Fellowship
- Accepted
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2024-10-07Accepted
- Available
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2024-11-26Published
- Caltech groups
- Astronomy Department
- Publication Status
- Published