dwarf nova

A dwarf nova (DN) is the flash of a type of cataclysmic variable star (a white dwarf accreting matter from a binary companion), that is generally less bright than a (typical) nova. Current theory ascribes dwarf novas to heating of accretion disk material due to a short-term increase in the accretion rate, i.e., some instability in the ongoing process. The term dwarf nova is also used to refer to the star, which is also termed a U Geminorum variable (UG). Some subtypes:

• UG SS Cygni variable (UGSS).
• UG SU Ursae Majoris (UGSU).
• UG WZ Sagittae (UGWZ).
• UG Z Camelopardalis (UGZ).