SPIN EQUILIBRIUM WITH OR WITHOUT GRAVITATIONAL WAVE EMISSION: THE CASE OF XTE J1814-338 AND SAX J1808.4-3658

In this Letter we present a new analysis of the torques acting on the accreting millisecond X-ray pulsars SAX J1808.4-3658 and XTE J1814-338, and show how our results can be used to constrain theoretical models of the spin evolution. In particular, we find upper limits on any spin-up/down phase of XTE J1814-338 of |ν-dot| < or approx. 1.5x10-14 Hzs-1 at 95% confidence level. We examine the possibility that a gravitational wave torque may be acting in these systems and suggest that a more likely scenario is that both systems are close to spin equilibrium, as set by the disk/magnetosphere interaction.