In this paper we discuss the recently discovered radio transient in the nuclear region of M 82 .
It has been suggested that this source is an X-ray binary , which , given the radio flux density , would require an X-ray luminosity , L _ { X } \sim 6 \times 10 ^ { 42 } erg s ^ { -1 } if it were a stellar mass black hole that followed established empirical relations for X-ray binaries .
The source is not detected in the analysis of the X-ray archival data .
Using a 99 % confidence level upper limit we find that L _ { X } \leq 1.8 \times 10 ^ { 37 } erg s ^ { -1 } and 1.5 \times 10 ^ { 37 } erg s ^ { -1 } , using powerlaw and disk blackbody models respectively .
The source is thus unlikely to be a traditional microquasar , but could be a system similar to SS 433 , a Galactic microquasar with a high ratio of radio to X-ray luminosity .