Zooming in on a sleeping giant: milliarcsecond high sensitivity array imaging of the black hole binary V404 Cyg in quiescence

Miller-Jones, J.C.A., Gallo, E., Rupen, M.P., Mioduszewski, A.J., Brisken, W.F., Fender, R.P., Jonker, P.G. and Maccarone, T.J. (2008) Zooming in on a sleeping giant: milliarcsecond high sensitivity array imaging of the black hole binary V404 Cyg in quiescence. Monthly Notices of the Royal Astronomical Society, 388 (4), 1751-1758. (doi:10.1111/j.1365-2966.2008.13495.x).

Abstract

Observations of the black hole X-ray binary V404 Cyg with the very long baseline interferometer the High Sensitivity Array (HSA) have detected the source at a frequency of 8.4GHz, providing a source position accurate to 0.3mas relative to the calibrator source. The observations put an upper limit of 1.3mas on the source size (5.2au at 4kpc) and a lower limit of 7 × 106 K on its brightness temperature during the normal quiescent state, implying that the radio emission must be non-thermal, most probably synchrotron radiation, possibly from a jet. The radio light curves show a short flare, with a rise time of ~30min, confirming that the source remains active in the quiescent state.

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