Quantifying the Accretion Rate of V1500 Cygni

V1500 Cyg is an old classical nova that harbors a highly magnetic white dwarf primary. V1500 Cyg erupted in 1975, but recent infrared observations reveal a source with large amplitude variations that had been ascribed to irradiation of the secondary star by the hot primary. We find, however, that a substantial fraction of the orbitally modulated light is due to cyclotron emission, suggesting magnetic accretion is the dominant irradiation source. Thus, V1500 Cyg has an accretion rate that is much higher than found in other old novae. Such anomalously high accretion rates could allow the mass of the white dwarfs in such systems to grow to the Chandrasekhar limit, and thus highly magnetic old novae are excellent candidates for producing Type Ia SNe.