RUTH ANGUS ASTRONOMY

This method of inferring a stellar age, given a rotation period is called gyrochronology. We used asteroseismic ages for around 300 Kepler field stars from Chaplin et al. (2014), with rotation periods from Garcia et al. (2014), to calibrate gyrochronology for old field stars. It seems as though stellar ages predicted by gyrochronology do not agree with those predicted by asteroseismology for these stars (see image right). The stars plotted are around solar mass and the old ones fall below the models that were calibrated using the the Sun (red) and nearby field stars (blue). Gyrochronology predicts that these stars are younger than their asteroseismic ages. Or put another way, these stars are too rapidly rotating for their age and mass. Are these stars binaries? Are the rotation periods wrong? Are the asteroseismic ages wrong? Are the models wrong? We still don't know the answers to these questions!

The Systematics-Insensitive Periodogram (SIP) is a simple extension of a sine-fitting periodogram, where instead of modelling the data with a sinusoidal signal alone, you model the data with a sinusoid plus a noise model. This technique avoids the necessity for directly detrending the light curves and should be better for detecting low amplitude signals in the data than a traditional 'detrend-then-compute-a-periodogram' approach.