Calibrating Gyrochronology using Kepler Asteroseismic targets

This is where I use rotation periods measured in K-ACF, as well as the asteroseismically determined ages and masses for the 505 stars in Chaplin et al, 2013 to calibrate the existing Gyrochronology relations of Barnes (2007) and(?) Mamajek and Hillenbrand (2008).

Stars can be used as clocks. The way in which they spin is thought to be tied to their mass and age so predictably that we can tell how old they are purely from how quickly they are rotating. At least that's what we thought, until now.

The method of dating stars using their rotation periods is called gyrochronology and here's a little background about how it works. When stars are born they have some rate of rotation. That's just because whatever gas cloud they form from will also be slowly rotating. As a cloud collapses into a proto-star it will rotate more rapidly due to angular momentum conservation and by the time it's a fully fledged main-sequence star it will be rotating once every few hours to few days. One would expect that these initial rotation periods are random. These gas clouds have some distrubution of rotation periods and it follows that the stars will too. That seems to be the case... for the young stars. After about 500 million years something strange happens: stars of the same mass and age all seems to rotate at the same rate. But how can that happen if they're all born with different rotation periods? The answer lies in the fact that stars spin-down. Once they arrive on the main-sequence they begin to lose angular momentum via their magnetic wind. The answer is that although they start out with different rates of rotation, they all undergo different rotational evolution over the first 500 million years of their lives: the fast rotators decelerate rapidly and the slow rotatators decelerate slowly.