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The pulsar J1203+0038 rotates with a frequency $\nu\approx 592$ Hz and hasbeen observed to transition between a radio state, during which it is visibleas a millisecond radio pulsar, and and a Low Mass X-ray Binary state, duringwhich accretion powered X-ray pulsations are visible. Timing during the twophases reveals that during the LMXB phase the neutron star is spinning down ata rate of $\dot{\nu}\approx -3 \times 10^{-15}$ Hz/s, which is approximately27\% faster than the rate measured during the radio phase, $\dot{\nu}\approx-2.4 \times 10^{-15}$ Hz/s, and at odds with the predictions of accretionmodels. In this letter we suggest that the increase in spin-down rate iscompatible with gravitational wave emission, and in particular to the creationof a `mountain' during the accretion phase. We show that asymmetries inpycno-nuclear reaction rates in the crust can lead to a large enough massquadrupole to explain the observed spin-down rate, which so far has no otherself-consistent explanation, and that radio timing at the onset of the nextmillisecond radio pulsar phase can test this scenario. Another possibility isthat an unstable $r$-mode with amplitude $\alpha\approx 5\times10^{-8}$ may bepresent in the system.

Are gravitational waves spinning down PSR J1023+0038?