Detecting Stellar Magnetic Cycles and Rotation Period Using UF’s Dharma Planet Survey

Francisco Mendez

Authors: Francisco Mendez, Jian Ge, Yinan Zhao, Kevin Willis, Benjamin Kimock, Nolan Grieves, Bo Ma, Dingshan Deng, Sun Yan, Derod Deal

Faculty Mentor:  Dr. Jian Ge

College:  College of Liberal Arts and Sciences


Stellar activity is the biggest noise source for small radial velocity measurements. Consequently, it makes low-mass exoplanet detection a challenge. We focus on the measurement of stellar magnetic cycles and rotation periods of 23 FGK type stars using two well-known activity indicators: The H alpha (656.3 nm) and Ca IRT (849.8 nm 854.2 nm, and 866.2 nm) lines. We analyzed the long-term variability to measure the magnetic cycles of these stars. Then, we used the Lomb-Scargle periodogram to detect the rotation period. Because of the short observation time span, we could not detect whole magnetic cycles, but instead phases. Our results show three different magnetic cycle phases: Active, Quiet, or Transition. Likewise, we were able to detect four different rotation phases: Significant, Not Significant, Stable, and Immeasurable rotation. The most significant result is shown in the star HD115043. We measured a rotation period of ~6 days using both activity indicators. This result can be supported with previous literature work. We concluded that each activity indicator is sensitive to different types of activity. In addition, the Ca IRT is not sensitive enough for rotation measurements; however, we could still calculate this parameter using it, and support our results with the literature.

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