Monitor: rotation periods of low-mass stars in young open clusters

Jonathan Irwin (CfA)

The rotation rate of a star is one of the few fundamental stellar properties which is directly accessible observationally, by measuring photometric periods. I summarise results from rotation period measurements for F-M stars in a range of clusters spanning ages of ~1 Myr to 250 Myr, including data from the literature, and a sample of new periods from the Monitor project, a large-scale time-domain photometric survey of young open clusters and star-forming regions. The results confirm a strong mass-dependence of the rotational period distributions also seen in v sin i measurements, which appears to persist from the youngest ages in the sample to the zero age main sequence, evolving in a manner which can be approximately reproduced by simple models of rotational evolution. The origin of this mass-dependence is still not clear however. Finally, I summarise prospects for future work in this area, highlighting the lack of measurements for mid to late M-dwarfs at intermediate ages (~500 Myr), which are important for constraining the evolution at the low-mass end.