2016/06/30 by Travis S. Metcalfe, Ricky Egeland, Jennifer van Saders · 1 citation
Physics and Astronomy · #astro-ph.SR
paper · pdf · doi:10.3847/2041-8205/826/1/l2
published as Astrophys.J 826, L2 (2016) · 7 pages, 2 tables, 2 figures. ApJL accepted, Colloquium available at https://youtu.be/_3MdLAt8i-o
arxiv created 2016/08/26 · arxiv updated 2016/08/29
Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation-age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro~2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation-age relations. We use these data along with a sample of well characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.