HD 4915: A Maunder Minimum Candidate
Abstract
We study the magnetic activity cycle of HD 4915 using the Ca ii HK emission line strengths measured by Keck I/High Resolution Echelle Spectrometer (HIRES) spectrograph. The star has been observed as a part of California Planet Search Program from 2006 to present. We note decreasing amplitude in the magnetic activity cycle, a pattern suggesting the star's entry into a Magnetic Grand Minimum state, reminiscent of the Sun's Maunder and Dalton Minima. We recommend further monitoring of the star to confirm the grand minimum nature of the dynamo, which would provide insight into the state of the Sun's chromosphere and the global magnetic field during its grand minima. We also recommend continued observations of HK emission lines, and ground- or space-based photometric observations to estimate the sunspot coverage.
Additional Information
© 2018 The American Astronomical Society. Received 2018 January 29; revised 2018 June 13; accepted 2018 June 28; published 2018 August 16. We thank the referee for a constructive report that improved this Letter, and for pointing us to the Donahue et al. identification of HD 3651 as an MGM candidate. We thank Eric Mamajek for useful discussions and for hunting down the early use of the term "Dalton Minimum."9 We also thank Thomas Beatty, Fabienne Bastien, Mark Giampapa, David Soderblom, and Larry Ramsey for useful discussions that improved the Letter. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. 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 Bibliographic Services, the SIMBAD database, operated at CDS, Strasbourg, France, and the AstroBetter blog and wiki. This material is based upon work supported by the NSF Postdoctoral Research Fellowship in Biology under grant No. AST-1602662. Facility: Keck:I (HIRES). -Attached Files
Published - Shah_2018_ApJL_863_L26.pdf
Submitted - 1801.09650.pdf
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Additional details
- Eprint ID
- 88858
- Resolver ID
- CaltechAUTHORS:20180816-110707560
- Pennsylvania State University
- Eberly College of Science
- Pennsylvania Space Grant Consortium
- W. M. Keck Foundation.
- NSF Astronomy and Astrophysics Fellowship
- AST-1602662
- Created
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2018-08-16Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department