Effects of rotation on the colours and line indices of stars. I - The Alpha Persei Cluster

Abstract

Analysis of the available observational data for the Alpha-Persei cluster members shows that rotation effects on the intermediate-band indices c1 and (u-b) are considerable. In c1, rotation produces a reddening of 0.040 magnitudes per 100 km/s. In (u-b), the effect for B stars is found to be 0.06 magnitudes per 100 km/s of V sin i. The binaries and peculiar stars are found to behave differently in the color excess (due to rotation) versus V sin i diagrams. These empirical effects can be utilized to recalibrate these color indices and also to separate members that are either chemically peculiar or in binary systems.