The faint 2011 outburst of the black hole X-ray binary candidate MAXI J1543-564

We report on a spectral-timing analysis of the black hole X-ray binary candidate MAXI J1543-564 during its 2011 outburst. All 99 pointed observations of this outburst obtained with the Rossi X-ray Timing Explorer (RXTE) were included in our study. We computed the fundamental diagrams commonly used to study black hole transients, and fitted power density and energy spectra to study the spectral and timing parameters along the outburst. The determination of timing parameters and hence of exact transitions between different states was hampered by the rather low count rate at which this outburst was observed. We detected two periods of exponential decay, one after the source was brightest, which was interrupted by several flares, and another one during the high soft state. The detection of these decays allowed us to obtain an estimate for the source distance of at least 8.5 kpc. This leaves two possible explanations for the observed low count rate; either the source has a distance similar to that of other black hole X-ray binary candidates and it is intrinsically faint, or it has a similar luminosity, but is located more than 12 kpc away from us. Furthermore, in the high/soft state the source spectrum appears to be completely disc dominated.