Search for Dwarf Novae in DASCH Scans Near M44

摘要

Dwarf novae (DNe) are a subclass of Cataclysmic Variables (CVs)with outbursts powered by a disk instability leading to a sudden increase inthe accretion rate. The Digital Access to a Sky Century at Harvard (DASCH)Collaboration is preparing to digitize over 500,000 Harvard plates from the1880s to the 1980s with limiting magnitudes ranging from B = 14-19. As ademonstration project, we have scanned more than 500 plates in the fieldscentered on the galactic open cluster M44. There are twenty-one CVs in thefields within ten degrees of M44 covered by the scans Here we present thepreliminary results of DN outbursts of the known CVs to derive long-term DNoutburst duty cycles. In addition, a one hundred year light curve for a XM M-Newton source is also presented to demonstrate DASCH capabilities.