Back to Volume
Paper: The Age-Rotation-Activity Relation: From Myrs to Gyrs
Volume: 448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
Page: 269
Authors: Covey, K. R.; Agüeros, M. A.; Lemonias, J. J.; Law, N. M.; Kraus, A. L.; Palomar Transient Factory Collaboration
Abstract: Over the past 40 years, observational surveys have established the existence of a tight relationship between a star's age, rotation period, and magnetic activity. The age-rotation-activity relation is essential for understanding the interplay between, and evolution of, a star's angular momentum content and magnetic dynamo. It also provides a valuable age estimator for isolated field stars. While the age-rotation-activity relation has been studied extensively in clusters younger than 500 Myr, its subsequent evolution is less constrained. Empirically measured rotation periods are scarce at intermediate ages (i.e., Hyades or older), complicating attempts to test reports of a break in the age-activity relation near 1 Gyr (e.g., Pace & Pasquini 2004; Giardino et al. 2008). Using the Palomar Transient Factory (PTF), we have begun a survey of stellar rotation to map out the late-stage evolution of the age-rotation-activity relation: the Columbia/Cornell/Caltech PTF (CCCP) survey of open clusters. The first CCCP target is the nearby ∼600 Myr Hyades-analog Praesepe; we have constructed PTF light curves containing >150 measurements spanning more than three months for ∼650 cluster members. We measure rotation periods for 40 K & M cluster members, filling the gap between the periods previously reported for solar-type Hyads (Radick et al. 1987; Prosser et al. 1995) and for a handful of low-mass Praesepe members (Scholz & Eislöffel 2007). Our measurements indicate that Praesepe's period-color relation undergoes a transition at a characteristic spectral type of ∼M1 — from a well-defined singular relation at higher mass, to a more scattered distribution of both fast and slow-rotators at lower masses. The location of this transition is broadly consistent with expectations based on observations of younger clusters and the assumption that stellar-spin down is the dominant mechanism influencing angular momentum evolution at ∼600 Myr. Combining these data with archival X-ray observations and Hα measurements provides a portrait of the ∼600 Myr age-rotation-activity relation (see contribution by Lemonias et al. in these proceedings). In addition to presenting the results of our photometric monitoring of Praesepe, we summarize the status and future of the CCCP survey.
Back to Volume