  CAL83 is a prototype of the class of Super Soft X-ray Sources (SXS). It is a
binary consisting of a low mass secondary that is transferring mass onto a
white dwarf primary and is the only known SXS surrounded by an ionisation
nebula, made up of the interstellar medium (ISM) ionised by the source itself.
With the VIMOS IFU we obtained spectra over a 25\times25" field of view,
encompassing one quarter of the nebula. Emission line maps - H I, He II, [O
III], [N II], and [S II] - are produced in order to study the morphology of the
ionised gas. We include CAL83 on diagrams of various diagnostic ion ratios to
compare it to other X-ray ionised sources. Finally we computed some simple
models of the ionised gas around CAL83 and compare the predicted to the
observed spectra. CAL83 appears to have a fairly standard ionisation nebula as
far as the morphology goes: the edges where H is recombining are strong in the
low stage ionisation lines and the central, clumpy regions are stronger in the
higher stage ionisation lines. But the He II emission is unusual in being
confined to one side of CAL83 rather than being homogeneously distributed as
with the other ions. We model the CAL83 nebula with cloudy using model
parameters for SXSs found in the literature. The He II emission does not fit in
with model predictions; in fact none of the models is able to fit the observed
spectrum very well. The spectral line images of the region surrounding CAL83
are revealing and instructive. However, more modelling of the spectrum of the
ionised gas is necessary, and especially for the high-ionisation level emission
from CAL83. In particular, we wish to know if the He II emission and the other
nebular lines are powered by the same ionising source.
