A 33-Year Timing Solution of the Redback Millisecond Pulsar Terzan 5A

We present a 33.4-year timing solution of the redback pulsar system Terzan 5A (Ter5A). Redback pulsars are a class of millisecond pulsar with relativistic winds that strongly affect a close main sequence companion star. The ionized wind from the pulsar's ablation of its companion delays or completely obscures the regular pulses and perturbs the canonical "perfect'' astrophysical clock. Ter5A, also known as B1744-24A or J1748-2446A, has a 11.56 ms pulse period, a 0.1 solar mass dwarf companion star, and an orbital period of 1.82 hours. This system displays highly variable eclipsing and orbital perturbations. Using new timing techniques, we have determined a phase connected timing solution for this system over 33 years, the longest ever published for a redback pulsar. We find that the pulsar's spin variability is much larger than most globular cluster pulsars, and we see no evidence of strong correlations between orbital and spin variability of the pulsar. We also find that astrometric timing measurements are likely too strongly contaminated by this variability to be usable. Finally, we measure an orbital period contraction of -2.175 * 10^(-13), which is almost certainly the General Relativity-dominated orbital decay of the system.