A 12-year activity cycle for the nearby planet host star HD 219134

Johnson, Marshall C. and Endl, Michael and Cochran, William D. and Meschiari, Stefano and Robertson, Paul and MacQueen, Phillip J. and Brugamyer, Erik J. and Caldwell, Caroline and Hatzes, Artie P. and Ramirez, Ivan and Wittenmyer, Robert A. (2016) A 12-year activity cycle for the nearby planet host star HD 219134. The Astrophysical Journal, 821 (2). ISSN 0004-637X

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The nearby (6.5 pc) star HD 219134 was recently shown by Motalebi et al. and Vogt et al. to host several planets,
the innermost of which is transiting. We present 27 years of radial velocity (RV) observations of this star from the McDonald Observatory Planet Search program, and 19 years of stellar activity data. We detect a long-period
activity cycle measured in the Ca II SHK index, with a period of 4230±100 days (11.7 years), very similar to the 11 year solar activity cycle. Although the period of the Saturn-mass planet HD 219134 h is close to half that of the activity cycle, we argue that it is not an artifact due to stellar activity. We also find a significant periodicity in the SHK data due to stellar rotation with a period of 22.8 days. This is identical to the period of planet f identified by Vogt et al., suggesting that this RV signal might be caused by rotational modulation of stellar activity rather than a
planet. Analysis of our RVs allows us to detect the long-period planet HD 219134 h and the transiting super-Earth
HD 219134 b. Finally, we use our long time baseline to constrain the presence of longer period planets in the
system, excluding to 1s objects with M sin i > 0.36MJ at 12 years (corresponding to the orbital period of Jupiter)
and M sin i > 0.72MJ at a period of 16.4 years (assuming a circular orbit for an outer companion).

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version made accessible, in accordance with the copyright policy of the publisher.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 20 Mar 2017 07:00
Last Modified: 17 Aug 2017 05:20
Uncontrolled Keywords: stars; HD 219134; rotation; techniques; radial velocities; spectroscopic techniques
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.3847/0004-637X/821/2/74
URI: http://eprints.usq.edu.au/id/eprint/30647

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