Physical properties of the B and Be star populations of h and χ Persei

Abstract

We present a study of the B and Be star populations of the double cluster h and χ Persei. Blue optical spectroscopy is used to first measure projected rotational velocity, V sin i, effective surface temperature, T eff, and surface gravity, log g, for B-type sample stars, while available Strömgren photometry is used to calculate T eff and log g for the Be stars showing emission. In our sample of 104 objects for which we measured these stellar parameters, 28 are known or proposed Be stars. Of these Be stars, 22 show evidence of emission at the times of our observations, and furthermore, we find evidence in our data and the literature for at least 8 transient Be stars in the clusters. We find that the Be stars are not rotating near their critical velocity, contrary to the results of studies of similar open clusters. We compare the results of our analysis with other previous studies and find that the cluster members are more evolved than found by Huang & Gies but still retain much of their initial rotational angular momentum. © 2012. The American Astronomical Society. All rights reserved..