Continued Timing of PSR J1023+0038: A Unique Testbed for Accretion Physics

Three years ago, PSR J1023+0038 (J1023) transformed from a rotationpoweredmillisecond pulsar state to an accretiondiskdominated Xray pulsar state. Inthis state it shows coherent Xray pulsations indicating active accretion at lowluminosities. Using these pulsations we have discovered that in the Xray stateJ1023 is spinning down 27% faster than the radio state (Jaodand et al. 2016).Along with this unique, longterm Xray timing solution for a transitionalmillisecond pulsar (tMSP) we also find a change in average orbital periodderivative between states. Extending the span of our timing solution to apossible J1023 transition (back to radio) in the coming year(s) is critical tounderstand tMSP transitions and accretion physics. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]