Abstract
The existing radio and X-ray flux correlation for Galactic black holes in the hard and quiescent states relies on a sample which is mostly dominated by two sources (GX 339-4 and V404 Cyg) observed in a single outburst. In this paper, we report on a series of radio and X-ray observations of the recurrent black hole GX 339-4 with the Australia Telescope Compact Array, the Rossi X-ray Timing Explorer and the Swift satellites. With our new long term campaign, we now have a total of 88 quasi-simultaneous radio and X-ray observations of GX 339-4 during its hard state, covering a total of seven outbursts over a 15--year period. Our new measurements represent the largest sample for a stellar mass black hole, without any bias from distance uncertainties, over the largest flux variations and down to a level that could be close to quiescence, making GX 339-4 the reference source for comparison with other accreting sources (black holes, neutrons stars, white dwarfs and active galactic nuclei). Our results demonstrate a very strong and stable coupling between radio and X-ray emission, despite several outbursts of different nature and separated by a period of quiescence. The radio and X-ray luminosity correlation of the form L_X ~L_Rad^0.62 +/-0.01 confirms the non-linear coupling between the jet and the inner accretion flow powers and better defines the standard correlation track in the radio-X-ray diagram for stellar mass black holes. We further note epochs of deviations from the fit that significantly exceed the measurement uncertainties, especially during the formation and destruction of the compact jets ...[abridged]. We incorporated our new data in a more global study of black hole candidates strongly supporting a scale invariance in the jet-accretion coupling of accreting black holes, and confirms the existence of two populations of sources in the radio/X-ray diagram.
Highlights
Stellar mass black holes (BH) in accreting binaries undergo occasional outbursts with transitions between different spectral states, usually defined by their X-ray spectral and timing properties (McClintock & Remillard 2006; Belloni 2010)
Two main spectral states can be defined as follows: 1) the hard state is characterised by a comptonised X-ray spectrum with a weak or absent (e.g. Tomsick et al 2008) thermal contribution from the accretion disc, and the presence of powerful self-absorbed compact jets (Corbel et al 2000; Dhawan, Mirabel & Rodrıguez 2000; Fender 2001; Stirling et al 2001), 2) the soft state is mostly dominated by the thermal emission from the accretion disc and the absence of relativistic jets (Fender et al 1999; Coriat et al 2011b; Russell et al 2011)
The work on the radio/X-ray flux correlation by Corbel et al (2003) used data from 1997, when GX 339−4 was in a period of extended and persistent hard state, and data from the decay of the 1998/99 outburst
Summary
Stellar mass black holes (BH) in accreting binaries undergo occasional outbursts with transitions between different spectral states, usually defined by their X-ray spectral and timing properties (McClintock & Remillard 2006; Belloni 2010). Two main spectral states can be defined as follows: 1) the hard state is characterised by a comptonised X-ray spectrum with a weak or absent (e.g. Tomsick et al 2008) thermal contribution from the accretion disc, and the presence of powerful self-absorbed compact jets (Corbel et al 2000; Dhawan, Mirabel & Rodrıguez 2000; Fender 2001; Stirling et al 2001), 2) the soft state is mostly dominated by the thermal emission from the accretion disc and the absence of relativistic jets (Fender et al 1999; Coriat et al 2011b; Russell et al 2011). Emission from the companion star is usually negligible for low mass X-ray binaries in outburst
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