  M31-RV was an extraordinarily luminous (~10^6 Lsun) eruptive variable,
displaying very cool temperatures (roughly 1000 Kelvins) as it faded. The
photometric behavior of M31-RV (and several other very red novae, i.e. luminous
eruptive red variables) has led to several models of this apparently new class
of astrophysical object. One of the most detailed models is that of
"mergebursts": hypothetical mergers of close binary stars. These are predicted
to rival or exceed the brightest classical novae in luminosity, but to be much
cooler and redder than classical novae, and to become slowly hotter and bluer
as they age. This prediction suggests two stringent and definitive tests of the
mergeburst hypothesis. First, there should always be a cool red remnant, and
NOT a hot blue remnant at the site of such an outburst. Second, the inflated
envelope of a mergeburst event should be slowly contracting, hence it must
display a slowly rising effective temperature. We have located a luminous,
UV-bright object within 0.4 arcsec (1.5 sigma of the astrometric position) of
M31-RV in archival WFPC2 images taken 10 years after the outburst: it resembles
an old nova. Twenty years after the outburst, the object remains much too hot
to be a mergeburst. Its behavior remains consistent with that of theoretical
nova models which erupt on a low mass white dwarf. Future Hubble UV and visible
images could determine if the M31-RV analogs (in M85 and in M99) are also
behaving like old novae.
