Surveys of exoplanet host stars are valuable tools for assessing population level trends in exoplanets, and their outputs can include stellar ages, activity, and rotation periods. We extracted chromospheric activity measurements from the California-Kepler Survey Gaia survey spectra in order to probe connections between stellar activity and fundamental stellar properties. Building on the California Kepler Survey's legacy of 1189 planet host star stellar properties including temperature, surface gravity metallicity, and isochronal age, we add measurements of the Ca ii H and K lines as a proxy for chromospheric activity for 879 planet hosting stars. We used these chromospheric activity measurements to derive stellar rotation periods. We find a discrepancy between photometrically derived and activity-derived rotation periods for stars on the Rossby Ridge. These results support the theory of weakened magnetic braking. We find no evidence for metallicity-dependent activity relations, within the metallicity range of −0.2 to +0.3 dex. With our single epoch spectra we identify stars that are potentially in Maunder minimum–like state using a combination of log(R_(HK)′) and position below the main sequence. We do not yet have the multiyear time series needed to verify stars in Maunder minimum–like states. These results can help inform future theoretical studies that explore the relationship between stellar activity, stellar rotation, and magnetic dynamos.
The California-Kepler Survey. XI. A Survey of Chromospheric Activity through the Lens of Precise Stellar Properties
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1.
California Institute of Technology
Abstract
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
The authors extend thanks to Travis Metcalfe and Luke Bouma for helpful discussions on early versions of the paper. We also thank Ryan Rubenzahl, Sarah Blunt, and Aida Behmard for providing feedback during group discussions.
Some of 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. This research has made use of NASA's Astrophysics Data System. L.M.W. acknowledges support from the NASA-Keck Key Strategic Mission Support program (grant No. 80NSSC19K1475) and the NASA Exoplanet Research Program (grant No. 80NSSC23K0269). Support was provided by the Simons Foundation grant "Planetary Context of Habitability and Exobiology".
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 project would not have been possible without major allocations of Keck telescope time from the University of California, California Institute of Technology, the University of Hawaii, and NASA. This work utilized the Exoplanet Archive, SIMBAD, the Community Follow-up Program, and data from NASA's Kepler Space Telescope.
Facilities
Keck:I (HIRES) - KECK I Telescope, Kepler - The Kepler Mission
Software References
We made use of the following publicly available Python modules: astropy (Astropy Collaboration et al. 2013), matplotlib (Hunter 2007), numpy/scipy (van der Walt et al. 2011), and pandas (McKinney 2010). Interactive Data Language (IDL) was used to extract the spectral line information.
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Additional details
- ISSN
- 1538-4357
- W. M. Keck Foundation
- National Aeronautics and Space Administration
- 80NSSC19K1475
- National Aeronautics and Space Administration
- 80NSSC23K0269
- Simons Foundation
- Caltech groups
- Astronomy Department