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Abstract

PSRJ1910-5959A (J1910A) is a binary millisecond pulsar in a 0.837 day
circular orbit around a helium white dwarf (HeWD) companion. This pulsar is
located 6.3 arcmin away from the centre of the globular cluster NGC6752. Given
the large offset, the association of the pulsar to NGC6752 has been debated. We
have made use of two decades of archival Parkes 64-m "Murriyang" telescope data
and recently carried out observations with the MeerKAT telescope. We obtained
Pulse times of arrival using standard data reduction techniques and analysed
using Bayesian pulsar timing techniques. We analysed the pulsar's total
intensity and polarisation profile, to study the interstellar scattering along
the line of sight, and the pulsar's geometry by applying the rotating vector
model. We obtain precise measurements of several post-Keplerian parameters: the
range $r=0.202(6)T_\odot$ and shape s=0.999823(4) of the Shapiro delay, from
which we infer the orbital inclination to be $88.9^{+0.15}_{-0.14}\deg$ and the
masses of both the pulsar and the companion to be $1.55(7)M_{\odot}$ and
$0.202(6)M_{\odot}$ respectively; a secular change in the orbital period
$\dot{P}_{\rm b}=-53^{+7.4}_{-6.0}\times 10^{-15}$\,s\,s$^{-1}$ that proves the
association to NGGC6752 and a secular change in the projected semi-major axis
of the pulsar $\dot{x}= -40.7^{+7.3}_{-8.2}\times10^{-16}$\,s\,s$^{-1}$ that is
likely caused by the spin-orbit interaction from a misaligned HeWD spin, at
odds with the likely isolated binary evolution of the system. We also discuss
some theoretical models for the structure and evolution of WDs in NS-WD
binaries by using J1910A's companion as a test bed. J1910A is a rare system for
which several parameters of both the pulsar and the HeWD companion can be
accurately measured. As such, it is a test bed to discriminate between
alternative models for HeWD structure and cooling.