NOVA-PERSEI 1901 - DETECTION OF THE SITE OF ITS BRIGHTEST LIGHT-ECHO

The large bipolar nebula around GK Per, discovered originally by Bode et al, from IRAS data, has now been detected at H alpha. There is enha nced emission from the southwestern edge, where it is colliding with t he interstellar medium. The morphology of this ridge shows a striking similarity to the brightest of the light-echo features observed in 190 1 and 1902. Bode et al. interpreted this nebula as an ancient planetar y, but there are severe problems with this interpretation: for example , the oldest known nebulae are a factor of 100 younger than the minimu m age for a white dwarf in a nova. Two main explanations are considere d. The first is that the nebula is composed of material accumulated fr om past nova events, although both its smooth morphology and the remar kably asymmetric structure of the nova shell argue against this scenar io. The other is that it was produced during the quiescent mass-loss p hase of the central binary, since the mass-loss rate may be substantia lly enhanced in this system because of the evolved nature of the secon dary. A straightforward observational test of these possibilities is s uggested.