The California Legacy Survey. V. Chromospheric Activity Cycles in Main-sequence Stars

Creators: Isaacson, Howard^{1, 2}; Howard, Andrew W.³; Fulton, Benjamin^{3, 4}; Petigura, Erik A.⁵; Weiss, Lauren M.⁶; Kane, Stephen R.^{2, 7}; Carter, Brad²; Beard, Corey⁸; Giacalone, Steven³; Van Zandt, Judah⁵; Murphy, Joseph M. Akana⁹; Dai, Fei³; Chontos, Ashley^{10, 11}; Polanski, Alex S.¹²; Rice, Malena¹³; Lubin, Jack^{5, 8}; Brinkman, Casey¹⁰; Rubenzahl, Ryan A.³; Blunt, Sarah¹⁴; Yee, Samuel W.¹¹; MacDougall, Mason G.⁵; Dalba, Paul A.⁹; Tyler, Dakotah⁵; Behmard, Aida¹⁵; Angelo, Isabel⁵; Pidhorodetska, Daria⁷; Mayo, Andrew W.^{1, 16}; Holcomb, Rae⁸; Turtelboom, Emma V.¹; Hill, Michelle L.⁷; Bouma, Luke G.³; Zhang, Jingwen¹⁰; Crossfield, Ian J. M.¹²; Saunders, Nicholas¹⁰

1. University of California, Berkeley
2. University of Southern Queensland
3. California Institute of Technology
4. NASA Exoplanet Science Institute
5. University of California, Los Angeles
6. University of Notre Dame
7. University of California, Riverside
8. University of California, Irvine
9. University of California, Santa Cruz
10. University of Hawaii at Manoa
11. Princeton University
12. University of Kansas
13. Yale University
14. Northwestern University
15. American Museum of Natural History
16. University of Copenhagen

Abstract

We present optical spectroscopy of 710 solar neighborhood stars collected over 20 years to catalog chromospheric activity and search for stellar activity cycles. The California Legacy Survey stars are amenable to exoplanet detection using precise radial velocities, and we present their Ca ii H and K time series as a proxy for stellar and chromospheric activity. Using the High Resolution Echelle Spectrometer at Keck Observatory, we measured stellar flux in the cores of the Ca ii H and K lines to determine S-values on the Mount Wilson scale and the log(R'HK) metric, which is comparable across a wide range of spectral types. From the 710 stars, with 52,372 observations, 285 stars were sufficiently sampled to search for stellar activity cycles with periods of 2–25 yr, and 138 stars showed stellar cycles of varying length and amplitude. S-values can be used to mitigate stellar activity in the detection and characterization of exoplanets. We used them to probe stellar dynamos and to place the Sun's magnetic activity into context among solar neighborhood stars. Using precise stellar parameters and time-averaged activity measurements, we found tightly constrained cycle periods as a function of stellar temperature between log(R'HK) of −4.7 and −4.9, a range of activity in which nearly every star has a periodic cycle. These observations present the largest sample of spectroscopically determined stellar activity cycles to date.

Copyright and License

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 Daniel Huber, Simon Albrecht, Simon Murphy, and Aaron Householder for helpful comments, and Lee Rosenthal for his early work on CLS. And we thank the anonymous referee for constructive feedback during review.

This work was supported by NASA Keck PI Data Awards, administered by the NASA Exoplanet Science Institute. 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 made use of NASA's Astrophysics Data System.

This project would not have been possible without major allocations of Keck telescope time from the University of California, the California Institute of Technology, the University of Hawaii, and NASA. This work utilized the SIMBAD astronomical database.

Author contributions: H.I. conducted the analysis and wrote the paper. A.W.H. was an originator of the survey. B.F., E.A.P., and L.M.W. are original collaborators on CLS. S.R.K. and B.C. advised on the analysis. Authors C.B. to N.S. in the author list above provided comments on the paper and contributed to the observing effort in order of their appearance.

The data collected here, previously published and novel, was gathered on over 1500 individual nights by 152 unique observers. Without their contribution to astronomical data collection, this work would not be possible.

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.

Contributions

Facilities

Keck:I - KECK I Telescope (HIRES)

Software References

We made use of the following publicly available Python modules: Astropy (Astropy Collaboration et al. 2013, 2018, 2022), matplotlib (Hunter 2007), numpy (van der Walt et al. 2011), scipy (Virtanen et al. 2020), and pandas (McKinney 2010). IDL was used to extract the spectral line information (ENVI version 4.8; Exelis Visual Information Solutions, Boulder, Colorado).

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Resource type: Journal Article
Publisher: American Astronomical Society
Published in: Astrophysical Journal Supplement Series, 274(2), 35, ISSN: 0067-0049.
Languages: English