An Extremely Slow Nova?

The binary companion to the peculiar F supergiant HD 172481 is shown to be a Mira variable with a pulsation period of 312 days. Its characteristics are within the normal range found for solitary Miras of that period, although its pulsation amplitude and mass-loss rate (M(dot) ~ 3 x 10^{-6} solar masses per year) are higher than average. Reasons are given for suspecting that the F supergiant, which has L ~ 10^4 solar luminosities, is a white dwarf burning hydrogen accreted from its companion.