0620061

We propose to perform a 260 ks INTEGRAL ToO observation of a transient millisecond X-ray pulsar in outburst. The target can be either one of the eight known transient accreting millisecond X-ray pulsars in thecase of a new outburst or a newly observed object of this class. As these transient sources have broad astronomical interest an outburst will trigger ToO criteria with other X-ray observatories. Theseobservations can be coordinated in order to study the broad band spectrum in detail from hard to soft X-ray energies as well as the timing properties of the source during its outburst. This will allow us to disentangle the contribution of soft black body reflection (if any) and hard Comptonized spectral components as wellas the detection of discrete emission/absorption features or Type I X-ray bursts (if present). In particular we will be able to study the energy spectrum of these sources which is usually observed to be quite hard even in outburst in a broad band energy range and with unprecedented high sensitivity above 20 keV. The INTEGRAL observation will also allow a timing analysis in an interesting and yet unexplored energy range. [truncated! Please see actual data for full text]