  Two short X-ray exposures (< 3600 s each) of the radio-quiet Seyfert 1.2
galaxy UGC 3973 (Mrk 79) were conducted with XMM-Newton as part of an AGN
snap-shot survey. In this paper we concentrate on the significance and possible
origin of a narrow 8 keV (rest-frame) line-like emission feature detected with
the pn instrument during the second observation. Simulations show that the
feature is significant at 96.0-98.4% confidence, depending on what a priori
assumptions are made. The feature cannot be attributed to background
contamination and appears to be variable (or transient) since it was not
detected in the first observation of UGC 3973 six months earlier. However, a
constant feature cannot be completely dismissed, based on the 90% upper-limit
on the flux from the first observation. There is some indication that the
feature is variable over the duration of the second observation as well. We
discuss various models (e.g. Ni emission, recombination edges, outflows, disc
lines) which could potentially produce an emission feature at such energies.
