We report the results of an observation of the galactic black–hole binary 4U 1543-475 performed by XMM–Newton on 2002 August 18 , about two months after the start of an outburst detected by RXTE .
Despite the relatively low flux of the source , corresponding to a luminosity L _ { X } \sim 4 \times 10 ^ { 34 } erg s ^ { -1 } \sim 10 ^ { -5 } L _ { EDD } , we could obtain a good quality spectrum thanks to the high throughput of the XMM–Newton EPIC instrument .
The spectrum is well fit by a power law with photon index \Gamma =1.9–2 without any evidence for iron emission lines or for thermal emission from an accretion disk .
We could estimate an upper–limit on the disk bolometric luminosity as a function of the colour temperature : it is always lower than \sim 10 ^ { 33 } erg s ^ { -1 } , i.e .
less than 10 % of the source total luminosity .
Finally , we evaluated that the disk colour temperature must satisy the condition kT _ { col } < 0.25 keV in order to obtain an acceptable value for the disk inner radius .