Multicolor Photometry of the SU Majoris Dwarf Nova V1504 Cygni

On the basis of multicolor observations of the dwarf nova V1504 Cyg, made from 1988 to 2001 at the Crimean Astrophysical Observatory and at the Crimean Laboratory of the P. K. Shternberg State Astronomical Institute in bands of the standard BVR photometric system, the brightness characteristics and color indices were obtained for a superoutburst and normal outbursts of the star. At an outburst maximum V1504 Cyg is bluer than at a minimum, with the ascending branch of an outburst being characterized by redder color indices than the descending branch. A detailed analysis of the behavior of two outbursts is consistent with Smak's model A, in which an outburst is caused by temperature instability developing first in the outer parts of the accretion disk around the compact component of the binary system and propagating into the inner parts. The characteristics of the other outburst are consistent with Smak's model B, in which instability develops first in the inner parts of the disk. It is suggested that type A outbursts are typical of V1504 Cyg, while type B outbursts are rare.     

Multicolor Photometric Study of the NOVA V1494 Aql in 2002

R and I band CCD observations of the nova V1494 Aql during July-November 2002 are reported and the V, R, and I light curves are analyzed. The orbital light curve of this nova has an eclipse-like form with two unequal humps before and after the eclipse. The approach to the eclipse lasts twice as long as the emergence from it. The overall duration of the eclipse is about 0.45P _orb. The depth of eclipse increases with wavelength and averages 0^m.3 (V), 0^m.5 (R), and 0^m.7 (I). The secondary, shallow minimum has an average depth of 0^m.1 in R and I and about 0^m.03 in V. The hump at phase 0.65 is higher than the one at phase 0.17. The most probable explanation for the observed variations in the light with the phase of the orbital period may be self eclipsing of the accretion column in the magnetic exploding variable (white dwarf) together with partial eclipsing of the accretion region by the secondary component.