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

Abstract

Multiwavelength observations of Galactic black hole (GBH) transients during state transitions and in the low/hard state may provide detailed information on the accretion structure of these systems. The object 4U 1543-47 is a GBH transient that was covered exceptionally well in X-rays and the infrared (daily observations) and reasonably well in the optical and radio during its outburst decay in 2002. When all the available information is gathered from the intermediate and the low/hard states, 4U 1543-47 makes an important contribution to our understanding of state transitions and the role of outflows in the high-energy emission properties of black hole binaries. The evolution of the X-ray spectral and temporal properties and the infrared light curve place strong constraints on different models to explain the overall emission from accreting black holes. The overall spectral energy distribution is consistent with a synchrotron origin for the optical and infrared emission; however, the X-ray flux is above the power-law continuation of the optical and infrared flux. The infrared light curve, the HEXTE light curve, and the evolution of the X-ray photon index indicate that the major source of hard X-rays cannot be direct synchrotron radiation from an acceleration region in a jet for most of the outburst decay.