We perform a timing analysis on RXTE data of the accreting millisecond pulsar XTE J1751–305 observed during the April 2002 outburst .
After having corrected for Doppler effects on the pulse phases due to the orbital motion of the source , we performed a timing analysis on the phase delays , which gives , for the first time for this source , an estimate of the average spin frequency derivative < \dot { \nu } > = ( 3.7 \pm 1.0 ) \times 10 ^ { -13 } Hz/s .
We discuss the torque resulting from the spin-up of the neutron star deriving a dynamical estimate of the mass accretion rate and comparing it with the one obtained from X-ray flux .
Constraints on the distance to the source are discussed , leading to a lower limit of \sim 6.7 kpc .