  The divergent part of the one-loop effective action in Chiral Perturbation
Theory with virtual photons has been evaluated in an arbitrary covariant gauge.
The differential operator, that emerges in the functional determinant, is of a
non-minimal type, for which the standard heat kernel methods are not directly
applicable. Both SU(2) and SU(3) cases have been worked out. A comparison with
existing results in the literature is given.
