Does phi Herculis have a corona ?

Abstract

High resolution IUE spectra of Phi Herculis have been searched for indicators of a chromosphere or transition region but none have been found, which could mean that the soft X-rays observed by HEAO-1 may have an alternative origin than a conventional corona in this Hg-Mn star. The possibility that white dwarfs could be responsible for the X-rays from this and some other similar stars is raised.