The unusual radio transient in M82: an SS 433 analogue?

TL;DR

This paper analyzes a radio transient in M82, suggesting it is unlikely a typical microquasar due to low X-ray luminosity, and may instead resemble SS 433, a Galactic microquasar with high radio to X-ray ratio.

Contribution

The study provides new constraints on the nature of the M82 radio transient, proposing it as an SS 433 analogue rather than a traditional microquasar.

Findings

X-ray luminosity upper limits are much lower than expected for a stellar mass black hole.

The source's properties are consistent with an SS 433-like system.

It is unlikely to be a typical microquasar based on X-ray data.

Abstract

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, $L_{\rm X}\,\sim6\times10^{42}$\,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 $L_{\rm X} \leq 1.8 \times 10^{37}$\,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.