The rotation period distribution of pre-main-sequence stars in and around the Orion nebula.
STASSUN K.G., MATHIEU R.D., MAZEH T. and VRBA F.J.
Abstract (from CDS):
We report rotation periods for 254 stars in an area 40'x80' centered on the Orion Nebula. We show that these stars are likely members of the young (∼106 yr) Orion OBIc/d association. The rotation period distribution we determine, which is sensitive to periods 0.1<P<8 days, shows a sharp cutoff for periods P<0.5 days, corresponding to breakup velocity for these stars. Above 0.5 days the distribution is consistent with a uniform distribution; we do not find evidence for a ``gap'' of periods at 4-5 days. We find signatures of active accretion among stars at all periods; active accretion does not occur preferentially among slow rotators in our sample. We find no correlation between rotation period and near-IR signatures of circumstellar disks. In addition, we show that the distribution of vsini among stars in our sample bears striking resemblance to that of low-mass Pleiades stars. We discuss the implications of our findings for the evolution of stellar angular momentum during the pre-main-sequence phase. We argue that all stars in our sample must still deplete angular momentum by factors of roughly 5-10, if they are to preserve their vsini distribution over approximately the next 100 Myr. We consider in detail whether our findings are consistent with disk-regulated stellar rotation. We do not find observational evidence that magnetic disk-locking is the dominant mechanism in angular momentum evolution during the pre-main-sequence phase.