Testing the Disk Regulation Paradigm withSpitzerObservations. I. Rotation Periods of Pre–Main‐Sequence Stars in the IC 348 Cluster

Abstract

We present 105 stellar rotation periods in the young cluster IC 348, 75 of which are new detections, increasing the total number of known periods in this cluster to 143. The period distribution resembles that seen in the heart of the Orion Nebula cluster by Herbst and colleagues. Stars estimated to be less massive than 0.25 M☉ show a unimodal distribution of fast rotators (P ~ 1-2 days) and a tail of slower rotators, while stars estimated to be more massive than 0.25 M☉ show a bimodal distribution with peaks at ~2 and ~8 days. We combine all published rotation periods in IC 348 with Spitzer mid-IR (3.6, 4.5, 5.8, and 8.0 μm) photometry, an unprecedentedly efficient and reliable disk indicator, 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. We find some indication that the disk fraction decreases significantly for stars with very short periods (P 1.5 days), which 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.