Transient radio emission from the X-ray nova ASM 2000+25

Abstract

A transient radio source associated with the soft X-ray nova ASM 2000+25 has been observed with the VLA. A nondetection 9 days after the initial X-ray outburst was followed by detections at 1.49 and 4.9 GHz 22 days later. Forty to 60 days after outburst it was a rapidly decaying, optically thin source with flux densities proportional to t-4ν-0.5. The radio data can be fitted to a synchrotron radio source model of a homogeneous, adiabatically expanding sphere of relativistic electrons with an energy spectral index of 2.0.