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Session 107 - Open Clusters.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[107.03] Angular Momentum Evolution of Low-Mass Stars in Open Clusters

A. Krishnamurthi, D. M. Terndrup, M. H. Pinsonneault, K. Sellgren (Ohio State U.), J. R. Stauffer (CfA)

We present the initial results of a monitoring program conducted to determine the photometric rotational periods of low mass stars in the Pleiades. This is part of a large program to determine rotational periods for stars in different open clusters across a range in masses and ages. We have monitored stars of spectral type G - M in the Pleiades. We discuss the implications of our observations for the theories of angular momentum evolution in stars. We explore the correlations between rotational period and X-Ray and chromospheric activities.

We have constructed low mass stellar models with different assumptions about internal angular momentum transport, angular momentum loss, and accretion disk lifetimes in the pre-main-sequence phase of evolution. The effect of imposing a saturation on angular momentum loss at high rotation rates is also explored. We compare cluster rotation data with our models and discuss the implications for the models of angular momentum loss. We find that the inferred star-disk coupling timecale required to reproduce the observed rotation rates in young clusters is a strong function of the timescale for internal angular momentum transport and that different scenarios make different predictions for clusters younger than the Pleiades.

Program listing for Thursday