First microquasar outside of our Galaxy found

A new paper by Matthew Middleton (previously at the University of Durham, now University of Amsterdam) and his large international team of co-authors has been published in Nature, bringing together X-ray and radio observations of a source in our neighbouring galaxy, M31 or Andromeda. The authors were able to characterise this source as a rare highly compact, accreting, ultraluminous Black Hole. The European Space Agency’s XMM-Newton satellite first detected XMMU J004243.6+412519 in early 2012 and recorded a peak luminosity of 1.26 x 1039 erg per second, from which the researchers could calculate a mass accretion rate close to the theoretical maximum (Eddington limit).

Based on follow-up observations in X-ray and radio, the team found that the source’s emissions were variable, indicating that they were not nebular in origin but rather due to a highly compact region that emits relativistic jets. One of the authors, CAASTRO Associate Investigator Jean-Pierre Macquart (Curtin University), was involved in the scintillation analysis of this study.

Thanks to having collected both X-ray and radio data, the team can be confident that their discovery is a Black Hole with an estimated stellar mass of approximately ten times that of our Sun. It appears to be dominated by its accretion disk that is drawing from a lower-mass companion star. Only four such objects have been previously found in our Milky Way, and XMMU J004243.6+412519 is the first of these ‘microquasars’ that is located outside of our Galaxy.

Publication details:

Middleton, M. J., Miller-Jones, J. C. A., Markoff, S., Fender, R., Henze, M., Hurley-Walker, N., Scaife, A. M. M., Roberts, T. P., Walton, D., Carpenter, J., Macquart, J-P., Bower, G. C., Gurwell, M., Pietsch, W., Haberl, F., Harris, J., Daniel, M., Miah, M., Done, C., Morgan, J., Dickinson, H., Charles, P., Burwitz, V., Della Valle, M., Freyberg, M., Greiner, J., Hernanz, M., Hartmann, D. H., Hatzidimitriou, D., Riffeser, A., Sala, G., Seitz, S., Reig, P., Rau, A., Orio, M., Titterington, D., and Grainge, K. in Nature (December 2012)

Bright radio emission from an ultraluminous stellar-mass microquasar in M31