IY UMa: accretion disc evolution after superoutburst

Abstract

CCD photometry of the newly discovered eclipsing dwarf nova IY UMa is used to study the physical properties of the accretion disc in the late decline and quiescence stages. Eclipse mapping analysis shows that in these stages the accretion disc is cool with approximately flat radial brightness temperature distribution and T_BR about 5000-5500 K. The hot spot is found to lie close along the stream trajectory at distance 0.36a and 0.25a from the disc center in February and March. The orbital hump strength decreases by about 30 % in a month. Taking the smallest possible size of the hot spot, we derive an upper limit for its brightness temperature, 15900 K and 13800 K, respectively.