Multiwavelength Observations of the Galactic Black Hole Transient 4U 1543−47 during Outburst Decay: State Transitions and Jet Contribution

Multiwavelength observations of Galactic black hole (GBH) transients duringthe state transitions and in the low/hard state may provide detailedinformation on the accretion structure of these systems. 4U1543-47 is a GBHtransient that was covered exceptionally well in X-ray and infrared (dailyobservations) and reasonably well in optical and radio during its outburstdecay in 2002. When all the available information is gathered in theintermediate and the low/hard state, 4U1543-47 makes an important contributionto our understanding of state transitions and the role of outflows on the highenergy emission properties of black hole binaries. The evolution of the X-rayspectral and temporal properties and the IR light curve place strongconstraints on different models for explaining the overall emission fromaccreting black holes. The overall spectral energy distribution is consistentwith synchrotron origin for the optical and infrared emission, however, theX-ray flux is above the power-law continuation of the optical and infraredflux. The infrared light curve, the HEXTE light curve and the evolution of theX-ray photon index indicate that the major source of hard X-rays cannot bedirect synchrotron radiation from an acceleration region in a jet for most ofthe outburst decay.Comment: 11 pages, 8 figures, revised version accepted by the Astrophysical Journa