  M31 RV is a luminous red variable star that appeared for several months in
the bulge of M31 during 1988. Unlike classical novae, M31 RV was cool
throughout its outburst. Interest in this object has revived recently because
of its strong resemblance to V838 Mon, a luminous Galactic variable star that
appeared in 2002 and is illuminating a spectacular light echo, and has evolved
to ever-cooler surface temperatures. V4332 Sgr is a third object which was also
a red supergiant throughout its eruption.
  We have examined archival Hubble Space Telescope (HST) images of the site of
M31 RV, obtained fortuitously in 1999 with the WFPC2 camera in parallel mode
during spectroscopic observations of the nucleus of M31. We located the site of
M31 RV in the HST frames precisely through astrometric registration with
ground-based CCD images, including several taken during the outburst. No light
echo is seen at the M31 RV site, implying that M31 RV is not surrounded by
circumstellar (or interstellar) dust similar to that around V838 Mon, or that
its extent is less than ~1.7 pc.
  The stellar population at the outburst site consists purely of old red
giants; there is no young population, such as seen around V838 Mon. There are
no stars of unusual color at the site, suggesting that M31 RV had faded below
HST detectability in the 11 years since outburst, that it is an unresolved
companion of one of the red giants in the field, or that it is one of the red
giants. We suggest future observations that may help decide among these
possibilities.
