Timing of a young mildly recycled pulsar with a massive white dwarf companion

We report on timing observations of the recently discovered binary pulsar PSR J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is in a 9.4-h orbit with a massive, M_WD > 0.93 M_☉, white dwarf (WD) companion. We present, for the first time, a phase-coherent timing solution, with precise spin, astrometric and Keplerian orbital parameters. This shows that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order of magnitude than any other recycled pulsar-massive WD system. We derive an upper limit on the true age of the system of 150 Myr. We investigate the formation of PSR J1952+2630 using detailed modelling of the mass-transfer process from a naked helium star on to the neutron star following a common-envelope phase (Case BB Roche lobe overflow). From our modelling of the progenitor system, we constrain the accretion efficiency of the neutron star, which suggests a value between 100 and 300 per cent of the Eddington accretion limit. We present numerical models of the chemical structure of a possible oxygen-neon-magnesium WD companion. Furthermore, we calculate the past and the future spin evolution of PSR J1952+2630, until the system merges in about 3.4 Gyr due to gravitational wave emission. Although we detect no relativistic effects in our timing analysis, we show that several such effects will become measurable with continued observations over the next 10 yr; thus, PSR J1952+2630 has potential as a testbed for gravitational theories....