Bright radio emission from an ultraluminous stellar-mass microquasar in M 31

• Published in: Nature (London) Vol. 493; no. 7431; pp. 187 - 190
• Main Authors: Middleton, Matthew J., Miller-Jones, James C. A., Markoff, Sera, Fender, Rob, Henze, Martin, Hurley-Walker, Natasha, Scaife, Anna M. M., Roberts, Timothy P., Walton, Dominic, Carpenter, John, Macquart, Jean-Pierre, Bower, Geoffrey C., Gurwell, Mark, Pietsch, Wolfgang, Haberl, Frank, Harris, Jonathan, Daniel, Michael, Miah, Junayd, Done, Chris, Morgan, John S., Dickinson, Hugh, Charles, Phil, Burwitz, Vadim, Valle, Massimo Della, Freyberg, Michael, Greiner, Jochen, Hernanz, Margarita, Hartmann, Dieter H., Hatzidimitriou, Despina, Riffeser, Arno, Sala, Gloria, Seitz, Stella, Reig, Pablo, Rau, Arne, Orio, Marina, Titterington, David, Grainge, Keith
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.01.2013; Nature Publishing Group
• Subjects: 639/33/34/864; 639/624/400/1106; Accretion; Astronomy; Astrophysics; Black holes; Black holes (astronomy); Emissions; Environmental aspects; Humanities and Social Sciences; letter; Luminosity; Luminosity (Astronomy); Microquasars; multidisciplinary; Observations; Radio; Radio emission; Science; Stars & galaxies; X-ray sources; X-rays; Australia; United Kingdom; Netherlands
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature11697

A new ultraluminous X-ray source has been discovered in M 31, whose variability and associated bright, compact radio emission identify it as a stellar-mass black hole accreting close to the Eddington limit. The ULX factor in the Andromeda galaxy Ultra-luminous X-ray sources, or ULXs, are a subject of controversy as their extreme luminosities have not yet been satisfactorily explained. Here Matthew Middleton et al . report radio and X-ray observations of a bright new X-ray source in the nearby M31 Andromeda galaxy. Its radio luminosity is extremely high and variable on a timescale of tens of minutes, implying a highly compact source powered by accretion onto a stellar-mass black hole at close to the Eddington limit, the theoretical maximum rate of matter infall. The authors speculate that using the latest highly sensitive radio telescopes, future observations of transient ULX systems in nearby galaxies will reveal the causal relationship between the accretion flow and the powerful jet emission. A subset of ultraluminous X-ray sources (those with luminosities of less than 10 40  erg s −1 ; ref. 1 ) are thought to be powered by the accretion of gas onto black holes with masses of ∼5–20 , probably by means of an accretion disk 2 , 3 . The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole 4 , 5 , with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way 6 , and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10 39  erg s −1 . The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.