Parkes observations for project P1021 semester 2022APRS_04

Brief description

We propose to continue our observations of PSR J1653-4518 and PSR J1812-15, a pair of long spin-period binary pulsars which both show degrees of orbitally-dependent variability. Binary pulsars are valuable objects of scientific study, allowing for multiple applications including tests of gravity, probes of the neutron star equation of state, and fossil records of stellar evolution. Long spin-period pulsars in binary systems are generally much rarer than faster-spinning `recycled’ pulsars, and represent an under-explored region of pulsar binary evolution. This is particularly true of PSR J1812-15, for which only one other pulsar (B1718-19) seems remotely comparable.

Based on previous Parkes proposals, our understanding of these pulsars has significantly increased (including the development of a timing solution for PSR J1653-4518), such that we anticipate their publication in early 2022. However, a minimal low-cadence timing campaign is still required to pursue lingering questions regarding both pulsars. For PSR J1812-15, this data is required to address ongoing problems with phase connection, which may be caused by an undiagnosed glitch or other un-modelled timing effect. For PSR J1653-4518, this data is required to maintain phase-connection in support of a multifrequency observing campaign targeting high-frequency emission during the pulsar’s next anticipated eclipse in November 2022 (an effect seen in similar binary systems). These observations will set up additional publishable results beyond the anticipated near-term publications in early 2022.