# A 12-Year Activity Cycle for HD 219134

@article{Johnson2016A1A,
title={A 12-Year Activity Cycle for HD 219134},
author={Marshall C. Johnson and Michael Endl and William D. Cochran and Stefano Meschiari and Paul Robertson and P. Macqueen and Erik J. Brugamyer and Caroline Caldwell and A. P. Hatzes and Iv'an Ram'irez and Robert A. Wittenmyer},
journal={arXiv: Earth and Planetary Astrophysics},
year={2016}
}
• Published 16 February 2016
• Physics, Geology
• arXiv: Earth and Planetary Astrophysics
The nearby (6.5 pc) star HD 219134 was recently shown by Motalebi et al. (2015) and Vogt et al. (2015) to host several planets, the innermost of which is transiting. We present twenty-seven years of radial velocity observations of this star from the McDonald Observatory Planet Search program, and nineteen years of stellar activity data. We detect a long-period activity cycle measured in the Ca II $S_{HK}$ index, with a period of $4230 \pm 100$ days (11.7 years), very similar to the 11-year…

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