First detection of radio emission from a dwarf nova

Abstract

The dwarf novae represent a class of cataclysmic variable stars that typically exhibit random optical outbursts of 2–6 mag with mean outburst periods of 10–150 days. Dwarf novae are close binary systems composed of a late-type star which fills its critical Roche lobe and a white dwarf companion. The white dwarf is surrounded by a luminous accretion disk sustained by mass transfer from the late-type star. The disk is the seat of the eruptions. Although radiation has been detected from dwarf novae from IR through X-ray energies, radio emission has never been reported from these objects. We describe here a search for radio emission at 4.75 GHz from dwarf novae that has been carried out with the 100-m telescope at Effelsberg, West Germany. We have searched for radio emission from six dwarf novae and a source was discovered at the position of SU UMa. The source could only be detected during optical outbursts and was below the threshold during quiescence. We suggest here that the radio emission arises from a non-thermal process.