A uvby-beta survey of northern-hemisphere active binaries. II. The m1 deficiency.

New photometric observations, using the uvby and H-beta systems of 72 northern-hemisphere active binaries are discussed in order to explain the main characteristics of their spectral light intensity distribution. Values of the parameter delta(m1) range from 0.0 to 0.3 mag, which cannot be explained in terms of metal underabundance alone. The existence of some mechanism responsible for such a color-index anomaly is thus suggested and is found to be in close relation with the involved degree of solar-type activity.