Chromospheric emission and rotation of main sequence stars

A qualitative approach to the problem of the chromospheric emission and rotation in main-sequence stars based on a consistent analysis of recently published data of stars from F8 to K5, is presented. The analysis has been performed using the following physical parameters: total power emission in the CaII K line, stellar rotation period from chromospheric emission variability, stellar ages from lithium abundance. The author derives expressions for the K line luminosity of both one solar mass stars and arbitrary stars. For the rotation period of main-sequence stars, an expression is derived which depends only on the masses and the ages. So, a direct result is obtained for the initial angular momentum and for the angular momentum at the Zero Age Main Sequence, setting t=0 and t=t0, respectively. (G.J.P.)