We shall now try to obtain an idea about the temperature of the shell using the presence of the elements observed in emission, as we have done in other papers of this series. Judging from the the ionization stage of the elements present in emission, we can say that the spectum corresponds to a late B or early A type object, a fact which would place the temperature of the shell at about 10 000 K. Assuming the photospheric temperature to be 15 000 K, and a black- body model for the two entities, one can calculate the radius of a surface which would dominate at wavelengths beyond 5 500 A, which is what one observes. It results a radius of 1.6 times the radius of a 15 000 degree star, which would correspond to the distance of the shell. This is rather close to the surface of the star, but is in line with the radius which can be deduced from the H alpha profile (Jaschek & Jaschek 1993) and which gives 2.7 stellar radii.