Parallel tracks in infrared versus X-ray emission in black hole X-ray transient outbursts: a hysteresis effect? |
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| Authors: | David M Russell Thomas J Maccarone Elmar G Körding Jeroen Homan |
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| Institution: | School of Physics and Astronomy, University of Southampton, Highfield, Southampton, Hampshire SO17 1BJ;Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 37-287 Cambridge, MA 02139, USA |
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| Abstract: | We report the discovery of a new hysteresis effect in black hole X-ray binary state transitions, that of the near-infrared (NIR) flux (which most likely originates in the jets) versus X-ray flux. We find, looking at existing data sets, that the IR emission of black hole X-ray transients appears to be weaker in the low/hard state rise of an outburst than the low/hard state decline of an outburst at a given X-ray luminosity. We discuss how this effect may be caused by a shift in the radiative efficiency of the inflowing or outflowing matter, or variations in the disc viscosity or the spectrum/power of the jet. In addition we show that there is a correlation (in slope but not in normalization) between IR and X-ray luminosities on the rise and decline, for all three low-mass black hole X-ray binaries with well-sampled IR and X-ray coverage: L NIR∝ L 0.5–0.7X . In the high/soft state this slope is much shallower; L NIR∝ L 0.1–0.2X , and we find that the NIR emission in this state is most likely dominated by the viscously heated (as opposed to X-ray heated) accretion disc in all three sources. |
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| Keywords: | accretion accretion discs black hole physics X-rays: binaries |
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