Long-term evolution of the fastest accreting millisecond pulsar IGR J00291+5934

We propose a 70 ks XMM observation of the fastest accreting millisecond pulsar discovered so far, IGR J00291+5934, during its next outburst. A measure of its spin and orbital parameters will put firm constraints on its long-term evolution and on the mechanisms (magneto-dipole emission, gravitational radiation) proposed to explain it. The lack of neutron stars observed to spin at frequencies close the centrifugal break-up (~1.5 kHz) will be tackled on an observational basis. The observation will also give accurate pulsar ephemeris, to allow a search for the gamma-ray counterpart expected to turn on as the source switches to a rotation-powered pulsar state during X-ray quiescence. This is a re-submission of a proposal approved for the AO11 and 12, and which was not triggered.