Testing the Disk Regulation Paradigm with Spitzer Observations. I.   Rotation Periods of Pre-main Sequence Stars in the IC 348 Cluster
  We present 75 new stellar rotation periods in the young cluster IC348. Stars estimated to be less massive than 0.25 Mo show a unimodal distribution with a peak at P ~1-2 d) and a tail of slower rotators, while stars estimated to be more massive than 0.2 Mo show a bimodal distribution with peaks at ~2 and ~8 d. We combine all published rotation periods in IC348 with Spitzer/IRAC photometry in order to test the disk-braking paradigm. We find no evidence that the tail of slow rotators in low-mass stars or the long period peak in high-mass stars are preferentially populated by objects with disks as might be expected based on the current disk-braking model. Also, we find no significant correlation between period and the magnitude of the IR-excess, regardless of the mass range considered. Our results do not support a strong correlation in this cluster between rotation period and the presence of a disk as predicted by disk-braking theory. Rather, they are consistent with the suggestion that the correlation between period and the amplitude of the (I-K) excess reported in the past is a secondary manifestation of the correlation between the amplitude of near-IR excess and mass. Finally, we find some indication that the disk fraction decreases significantly for stars with very short periods (P < 1.5 d). This is the only feature of our sample that could potentially be interpreted as evidence for disk braking. It has been proposed that the observational signatures of disk braking might be significantly masked by the intrinsic breadth of the initial period distribution. We argue that more rigorous modeling of angular momentum evolution and a quantitative analysis of the observational data are required before the disk-braking model can be regarded as inconsistent with observations. 
Lucas Cieza and Nairn Baliber