Bright radio emission from an ultraluminous stellar-mass microquasar in M 31
Done, Chris; Macquart, Jean-Pierre; Della Valle, Massimo; Middleton, Matthew J.; Roberts, Timothy P.; Haberl, Frank; Seitz, Stella; Bower, Geoffrey C.; Carpenter, John; Pietsch, Wolfgang; Orio, Marina; Freyberg, Michael; Henze, Martin; Hatzidimitriou, Despina; Greiner, Jochen; Hernanz, Margarita; Miller-Jones, James C. A.; Hurley-Walker, Natasha; Scaife, Anna M. M.; Markoff, Sera; Riffeser, Arno; Hartmann, Dieter H.; Fender, Rob; Grainge, Keith; Rau, Arne; Reig, Pablo; Sala, Gloria; Gurwell, Mark; Dickinson, Hugh; Burwitz, Vadim; Charles, Phil; Walton, Dominic; Titterington, David; Harris, Jonathan; Daniel, Michael; Miah, Junayd; Morgan, John S.
United Kingdom, Netherlands, Australia, Germany, United States, Sweden, South Africa, Italy, Spain, Greece
Abstract
A subset of ultraluminous X-ray sources (those with luminosities of less than 1040 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. 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, 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, 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 1039 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.