Volume 524, December 2010
|Number of page(s)||9|
|Published online||22 November 2010|
Steady jets from radiatively efficient hard states in GRS 1915+105
Onsala Space Observatory,
2 European Southern Observatory, Karl-Schwarzschild-Str 2, 85748 Garching, Germany
3 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
4 School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
5 Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
6 The University of Cambridge, Mullard Radio Astronomy Observatory, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
Received: 4 May 2010
Accepted: 3 September 2010
Recent studies of different X-ray binaries (XRBs) have shown a clear correlation between the radio and X-ray emission. We present evidence of a close relationship found between the radio and X-ray emission at different epochs for GRS 1915+105, using observations from the Ryle Telescope and Rossi X-ray Timing Explorer satellite. The strongest correlation was found during the hard state (also known as the “plateau” state), where a steady AU-scale jet is known to exist. Both the radio and X-ray emission were found to decay from the start of most plateau states, with the radio emission decaying faster. An empirical relationship of was then fitted to data taken only during the plateau state, resulting in a power-law index of ξ ~ 1.7 ± 0.3, which is significantly higher than in other black hole XRBs in a similar state. An advection-flow model was then fitted to this relationship and compared to the universal XRB relationship as described by Gallo et al. (2003, MNRAS, 344, 60). We conclude that either (I) the accretion disk in this source is radiatively efficient, even during the continuous outflow of a compact jet, which could also suggest a universal turn-over from radiatively inefficient to efficient for all stellar-mass black holes at a critical mass accretion rate (ṁc ≈ 1018.5 g/s); or (II) the X-rays in the plateau state are dominated by emission from the base of the jet and not the accretion disk (e.g. via inverse Compton scattering from the outflow).
Key words: accretion, accretion disks / black hole physics / radiation mechanisms: non-thermal / X-rays: binaries / stars: winds, outflows / ISM: jets and outflows
© ESO, 2010
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