THE PHYSICAL-PROPERTIES OF A SLOW NOVA IN THE BULGE OF M31

Observations are presented of an extremely slow nova that was discover ed in the bulge of M31 in 1986. The evolution of the object was monito red with subsequent yearly spectra until 1990, as part of a general sp ectroscopic survey of novae in M31 underway at McDonald Observatory. T he spectra cover the nova's evolution in the nebular phase, and these observations have made this nova the most extensively observed extraga lactic nova to date. This has provided a unique opportunity to make th e first detailed comparison of the evolution and properties of an extr agalactic nova with those in our own Galaxy. Since the nova is situate d in the bulge, it is likely that the object represents an outburst as sociated with an older population of novae, in contrast with Galactic novae which are almost entirely discovered as old disk objects. Althou gh the evolution of this object was unusually slow, the derived mass o f the nebula gas of 5 x 10(-5) M., electron temperature of 13,000 K, a nd abundances determined from an analysis of the emission line intensi ties are typical of those seen in Galactic slow novae: with a close to solar helium abundance (He/H = 0.13 +/- 0.02) and roughly solar abund ances of oxygen and neon. In a previous study evidence was found for a possible systematic difference in the proportion of the types of obse rved outbursts between M31 bulge novae and Galactic novae. For individ ual novae, however, these results indicate that the general disparate properties seen in nova outbursts probably overwhelm the relatively sm aller differences that might be expected when comparing novae from dif ferent stellar populations. The implications for using extragalactic n ovae as distance indicators are discussed.