  The RSCVn system Sigma Geminorum was observed by XMM-Newton on April 2001
during a large flare. We model the emission measure distribution (EMD) during
the flare and during a quiescence period. In the flare, a two phase behaviour
is found in which the cool plasma (kT < 2 keV) is not disturbed while a large
hot component, at temperatues of kT > 3 keV emerges. Fundamental limitations on
EMD modeling of high temperature plasmas are then discussed, in the context of
the Sigma Gem flare.
