Rotation of young low-mass stars in the Orion Nebula cluster flanking fields

We have photometrically monitored similar to 3600 young, low-mass stars in four 45'x45' fields in the outer Orion Nebula cluster, surrounding but not including the Trapezium region. The 281 periodic variables we find do not p roduce the expected bimodal distribution of rotation periods. There is no u nambiguous correlation of period with I-C - I-S, H - K-S, and U-V color exc esses or more indirect disk indicators; the slowest rotators are not necess arily the disk candidates, and the disk candidates are not necessarily the slow rotators, regardless of how one defines a disk candidate. To the exten t that the small numbers allow, the disk candidates represent a constant fr action of the total sample to P = 15 days, beyond which there are no disk c andidates, inconsistent with the hypothesis that the more slowly rotating s tars are more likely to have disks. We find an intriguing relationship betw een specific angular momentum (j) and some excesses, namely, H - K-s excess es and the strongest U-V excesses; whereas stars are found with j values ra nging over similar to 10(6)-10(8) km(2) s(-1), disk candidates with these e xcesses are restricted to 10(6.5) km(2) s(-1) <j <10(7.5) km(2) s(-1). A si milar relationship is not found for the I-C - K-S disk candidates, or in th e less excessive U-V candidates. There is no clear correlation between sign al amplitude and period or log j. Other investigators have found difference s in period distributions for stars more and less massive than 0.25 M-.; we find ambiguous evidence for differences in distributions of P and no diffe rence in those of log j on either side of this boundary, although for stars more massive than similar to0.6 values M-., values appear to cluster aroun d j = 10(7) km(2) s(-1). When comparing the log j distribution derived here with those for other clusters, we find that it is consistent with a popula tion of stars draining angular momentum into disks. We conclude that disk l ocking may be operating, but it is not the complete solution to the problem of angular momentum distributions in young stars. We find weak (1.5-2 sigm a) evidence for a change in stellar structure, spot coverage, and/or disk c haracteristics for stars redder than V - I-C similar to2.5 (type similar to M3, similar to0.25 M-.). We find that at least similar to 10% of the stars have identical light curves (shape and phase) between the two seasons of o ur observations, suggesting that the lifetime of the photospheric disturban ce causing periodic modulations in these stars is at least a year.