The Relation Between Absorption Velocity and Rate of Decline for Galactic Novae.

The relations between times of decline of light and the velocities of the principal and diffuse enhance,d absorption spectra are determined from observations of twenty- one galactic novae. These agree closely with relations between rates of development of spectra and the absorption velocities of six bright novae, as previously found by the author. It is concluded that (i) the spectral stage is a function of the difference of magnitude from maximum; (2) the time of decline or of spectral change is inversely proportional to the square of the velocity of the principal spectrum; and (s), in the average case, the velocity of the diffuse enhanced spectrum is twice that of the principal spectrum. The observed relations are radically different from that proposed by Zwicky, viz., the lifetime is directly proportional to the velocity. Such a relation, adjusted on a super~ nova, is fortuitously satisfied by some rapid common novae, but stars of slow and intermediate rate deviate very far from Zwicky's relation