  We find that the classical nova V723 Cas (1995) is still an active X-ray
source more than 12 years after outburst and analyze seven X-ray observations
carried out with Swift between 2006 January 31 and 2007 December 3. The average
count rate is 0.022+/-0.01 cts s^-1 but the source is variable within a factor
of two of the mean and does not show any signs of turning off. We present
supporting optical observations which show that between 2001 and 2006 an
underlying hot source was present with steadily increasing temperature. In
order to confirm that the X-ray emission is from V723 Cas, we extract a ROSAT
observation taken in 1990 and find that there was no X-ray source at the
position of the nova. The Swift XRT spectra resemble those of the Super Soft
X-ray binary Sources (SSS) which is confirmed by RXTE survey data which show no
X-ray emission above 2 keV between 1996 and 2007. Using blackbody fits we
constrain the effective temperature to between T_eff=(2.8-3.8)x10^5 K and a
bolometric luminosity >5x10^36 erg s^-1 and caution that luminosities from
blackbodies are generally overestimated and temperatures underestimated. We
discuss a number of possible explanations for the continuing X-ray activity,
including the intriguing possibility of steady hydrogen burning due to renewed
accretion.
