1540022

We propose to perform two 170 ks INTEGRAL ToO observations of a transient millisecond X-ray pulsar in outburst. To constrain the broadband spectrum we also request one 30 ks simultaneous NuSTAR and two 50 ks XMM-Newton observations. The target can be either one of the fifteen known transient accreting millisecond X-ray pulsars (AMXPs) in the case of a new outburst or a newly observed object of this class. These observations allow us to study the broad band spectrum in detail from hard to soft X-ray energies as well as the timing properties or eclipsing features of the source during its outburst. The high-statistics spectral information make it possible to disentangle the contributions of soft black body reflection (if any) and hard Comptonized spectral components. Moreover we will detect type-I X-ray bursts and/or for the first time also burst oscillations at high-energy (if present). In particular we will be able to study the energy spectrum in a broad energy range (0.1-300 keV) and with unprecedented high-sensitivity above 20 keV. The INTEGRAL and XMM-Newton observations will also allow a timing analysis to study the pulse profile time lags and pulsed spectrum and so will provide important constraints on emission mechanisms.Similar proposals were approved for the INTEGRAL AO2-AO14 cycles and during these years our ToO has been triggered eight times i.e. in 2003 we observed XTE J1807-294 in 2004 2005 2009 2011 and 2013 we triggered on newly discovered sources IGR J00291+5934 HETE 1900.1-2455 IGR J17511-3057 IGR J17498-2921 and IGR J18245-2452 respectively. In 2015 we triggered on IGR J00291+5934 and SAX J1748.5-2021 (data have been made public because it was not clear whether the source in outburst was the AMXP). [truncated! Please see actual data for full text]