Following the 2008 outburst decay of the black hole candidate H1743-322 in X-ray and radio

Autor: Jonker, P. G., Miller-Jones, J., Homan, J., Gallo, E., Rupen, M., Tomsick, J., Fender, R. P., Kaaret, P., Steeghs, D. T. H., Torres, M. A. P., Wijnands, R., Markoff, S., Lewin, W. H. G.
Rok vydání: 2009
Předmět:
Druh dokumentu: Working Paper
DOI: 10.1111/j.1365-2966.2009.15717.x
Popis: In this Paper we report on radio (VLA and ATCA) and X-ray (RXTE, Chandra and Swift) observations of the outburst decay of the transient black hole candidate H1743-322 in early 2008. We find that the X-ray light curve followed an exponential decay, leveling off towards its quiescent level. The exponential decay timescale is ~4 days and the quiescent flux corresponds to a luminosity of 3x10^32 (d/7.5 kpc)^2 erg/s. This together with the relation between quiescent X-ray luminosity and orbital period reported in the literature suggests that H1743-322 has an orbital period longer than ~10 hours. 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 N_H =2.3x10^22 cm^-2 limits the detected number of soft photons and thus the accuracy of the spectral fits.
Comment: 10 pages, 4 figures, accepted for publication by MNRAS
Databáze: arXiv
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