Description
The MgIIk emission line is a good indicator of the level of chromospheric activity in late-type stars. We investigate the dependence of this activity indicator on fundamental stellar parameters. To this purpose we use IUE observations of the MgIIk line in 225 late-type stars of luminosity classes I-V, with different levels of chromospheric activity. We first re-analyse the relation between MgIIk line luminosity and stellar absolute magnitude, performing linear fits to the points. The ratio of MgII surface flux to total surface flux is found to be independent of stellar luminosity for evolved stars and to increase with decreasing luminosity for dwarfs. We also analyse the MgIIk line surface flux-metallicity connection.
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