diagram for radio pulsars. The cross represents the position of the pulsar in IGR J00291 with period and period derivative as determined in Section 5.1 under the assumption that the observed spin-down is caused by magneto-dipole torques. I plot also the position of SAX J1808.4−3658 (red star; Patruno et al. 2009) and SWIFT J1756.9−2508 (blue circle; Patruno et al. 2010a). The latter has no detected spin-down during quiescence, and therefore the position is determined by using an upper limit on the spin-down.