the discoverers argue that if the source is further than 70 parsecs away, its high brightness temperature would require it to be powered by a coherent emission process. (if within 70 parsecs, the source could be either coherent or incoherent.) they also claim that most known coherent emission processes are unlikely explanations for the source. models proposed by others include a nulling pulsar, a pair of orbiting neutron stars, a radio-emitting white dwarf, and a pulsar precessing with a period of 77 minutes.