094022

In 2013 PSR J1023+0038 transformed from a rotation-powered radio millisecondpulsar state to an accretion-disk-dominated X-ray pulsar state where it hasremained since. In its current state it shows coherent X-ray pulsations at lowluminosities (~10^33 erg/s). Using XMM-Newton we have found that in the diskstate the pulsar is spinning down measurably faster compared to the radio-loudstate. This first of its kind long-term X-ray timing solution for anaccreting/transitional millisecond pulsar (tMSP) has helped us place usefulconstrains on models for disk-magnetosphere interaction. We propose to extendthe current timing solution with XMM-Newton through an impending J1023 statetransition in the near future in order to constrain accretion models. [truncated! Please see actual data for full text]