On the relation of hard X-ray peak flux and outburst waiting time in the black hole transient GX?339-4

摘要

Aims. We reinvestigate the empirical relationbetween the hard X-ray peak flux and the outburst waiting time foundpreviously in the black hole transient GX339-4. We verify therelation using the observed hard X-ray peak flux of the 2007 outburstof GX339-4, we clarify the nature of faint flares, and weestimate the lower limit to hard X-ray peak flux of the next outburst. Methods. We analyze Swift/BAT data obtained in thepast fouryears. Combined with the CGRO/BATSE and RXTE/HEXTElight curves, the observational data analyzed cover a period of18years. Results. The observation of the 2007 outburstconfirms the empirical relation discovered before, strengthening theapparent link between the mass in the accretion disk and the peakluminosity of the brightest hard state that the black hole transientcan reach. We also show that faint flares with peak fluxes lower thanabout 0.12crab do not affect the empirical relation. Wepredict that the hard X-ray peak flux of the next outburst should begreater than 0.65crab, which will make it at least the secondbrightest in hard X-rays since 1991. Key words: accretion, accretion disks -black hole physics - stars: individual: GX339-4