Observations of the outbursts of very-faint X-ray transients with XMM-Newton

We propose a 35 ks XMMNewton observation during the outburst of a veryfaintXray transient. These peculiar Xray binaries are underluminous by orders ofmagnitudes compared to the wellstudied classical (bright) Xray transientpopulation. Some of them have been identify as accreting neutron stars, whereasonly one black hole has been conclusively identified so far. However, the natureof the vast majority remains unclear. This XMMNewton observation will allow usto carry out a detailed spectral analysis of a very faint transient (< 10performed so far) in order to (i) shed light on the nature of this growingpopulation and (ii) the reason for their subluminous behaviour. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]