Following the 2008 outburst decay of the black hole candidate H 1743-322 in X-ray and radio

Peter G Jonker, James C A Miller-Jones, Jeroen Homan, Laura E Gallo, M. Rupen, J. A. Tomsick, R. P. Fender, P Kaaret, D. T.H. Steeghs, Manuel A P Torres, Rudy A D Wijnands, Sera B Markoff, W. H.G. Lewin

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In this paper, we report on radio (Very Large Array and Austrialian Telescope Compact Array) and X-ray (RXTE, Chandra and Swift) observations of the outburst decay of the transient black hole candidate H 1743-322 in early 2008. We find that the X-ray light curve followed an exponential decay, levelling off towards its quiescent level. The exponential decay time-scale is ≈4 days and the quiescent flux corresponds to a luminosity of erg s-1. This together with the relation between quiescent X-ray luminosity and orbital period reported in the literature suggests that H 1743-322 has an orbital period longer than ≈10 h. Both the radio and X-ray light curve show evidence for flares. The radio-X-ray correlation can be well described by a power-law with index ≈0.18. This is much lower than the index of ≈0.6-0.7 found for the decay of several black hole transients before. The radio spectral index measured during one of the radio flares while the source is in the low-hard state is -0.5 ± 0.15, which indicates that the radio emission is optically thin. This is unlike what has been found before in black hole sources in the low-hard state. We attribute the radio flares and the low index for the radio-X-ray correlation to the presence of shocks downstream the jet flow, triggered by ejection events earlier in the outburst. We find no evidence for a change in X-ray power-law spectral index during the decay, although the relatively high extinction of NH ≈ 2.3 × 1022 cm-2 limits the detected number of soft photons and thus the accuracy of the spectral fits.

Original languageEnglish
Pages (from-to)1255-1263
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Jan 2010
Externally publishedYes


  • Accretion, accretion discs
  • Binaries
  • Stars: individual: H 1743-322
  • X-rays: binaries

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