Strömgren Hβ -photometry of stars in dark clouds

We present uvbyβ photometry of 64 stars in 6 small dark clouds. From the photometry we infer approximate spectral types of the observed stars and derive distances and color excesses for each of them. We further derive new distance estimates to some of the globules based on the distances of individual stars possibly included in their peripheries. For clouds where sufficient target stars are available (CB3, CB52, and CB54), a clear trend of increasing linear polarization (as measured by Sen et al. 2000) with extinction is observed. We also find excellent correlation between polarization and extinction for the entire sample. The location of the stars on the polarization-extinction diagram is consistent with that for field stars found by Serkowski et al. (1975). The relation between polarization and extinction evident for the stars of our sample suggests perfect grain alignment and constant grain properties along each line of sight (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)