8. Concluding remarks
Since the spectral evolution of this nova after the light maximum has been very similar to that exhibited by normal classical novae (Iijima & Rosino 1996; 1997, and a detailed report will be made in a forthcoming paper), this object may not be classified in the group of symbiotic novae such as RT Ser, RR Tel, PU Vul etc., even if the evolution was very slow. It seems that RR Pic, HR Del and the present nova construct a group of rare classical novae characterized by slowest evolution.
Friedjung (1992) analysed the properties of HR Del in detail and suggested that the very slow explosion may have occurred under a critical condition. A recent theoretical work by Kato and Hachisu (1994) showed that extremely slow explosions may occur on a white dwarf with a mass of less than 0.6 . The derived mass 0.58 of the white dwarf in this system seems to be consistent with that expected from their model. Kovetz and Prialnik (1985) suggested that the explosion on such a low mass white dwarf could occur only under a very restricted condition. Detailed studies about this nova are required to advance our knowledge about the critical condition of novae's explosions.
© European Southern Observatory (ESO) 1998
Online publication: September 17, 1998