Parkes observations for project P1021 semester 2021APRS_25

We propose to continue our observations of PSR J1653-45, a 951-ms pulsar in a long, 1.5-yr orbit, which experiences apparent eclipses whose nature have yet to be fully understood. 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.\r\n\r\nBased upon previous Parkes and ATCA proposals, our understanding of this pulsar has significantly increased. We have detected the pulsar in previously unexplored regions of its orbit, localised its position, and have constrained the start of the eclipse, such that a targeted campaign in the 2021APRS semester (during which the next eclipse is expected) will provide the breakthrough needed to solve and understand this pulsar. We therefore propose a high-cadence campaign with observations at least 1.4 times more sensitive than any previously recorded with Parkes during the eclipse. These observations will constrain the end of the eclipse and ensure that we detect the pulsar as early and often as possible, leading to a phase connected timing solution which will unlock the pulsar’s scientific potential. Through this, we hope to gain a greater understanding of this pulsar’s properties (as well as those of its companion) and how it fits into this under-explored class of unrecycled pulsar binaries.