for solar mass stars, but discrepancies are apparent for stars with $0.6 \la M \la 1.0 M_{\odot}$. We also find that for late-K through early-M dwarf stars in this cluster rapid rotators tend to be bluer than slow rotators in $B-V$ but redder than slow rotators in $V-I_{C}$. This result supports the hypothesis that the significant discrepancy between the observed and predicted temperatures and radii of low-mass main sequence stars is due to stellar activity.'
author:
- 'J. D. Hartman, B. S. Gaudi, M. H. Pinsonneault, K. Z. Stanek, M. J. Holman, B. A. McLeod, S. Meibom, J. A. Barranco, and J. S. Kalirai'
title: 'Deep MMT[^1] Transit Survey of the Open Cluster M37 III: Stellar Rotation at 550 Myr'
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Introduction
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This paper is the third in a series of papers on a deep survey for transiting planets in the open cluster M37 (NGC 2099) using the MMT. In the first paper [@Hartman.07a Paper I] we introduced the survey, described the spectroscopic and photometric observations and the data reduction, determined the fundamental parameters (age, metallicity, distance and reddening) of the cluster, and obtained its mass and luminosity functions and radial density profile. In the second paper [@Hartman.07b Paper 