Parkes observations for project P1000 semester 2018OCTS_05

Hot subdwarf (sdB) stars are core-helium burning stars with thin hydrogen envelopes and masses around 0.5 Msun. A large fraction of sdBs are members of short-period binaries with periods below a few days. Orbital shrinkage through a common envelope phase is the only likely formation channel for such short-period sdB binaries. \r\nAlthough most of the companions are low mass main sequence stars or white dwarfs, one proposed evolutionary channel produces an sdB with a recycled pulsar companion where the pulsar forms after two common envelope phases and a short X-ray binary phase. Theoretical models predict that about 1% of the compact sdB binaries should have pulsar companions. \r\nSo far no pulsar companion to an sdB has yet been detected unambiguously whereas six candidates have been identified. Here we propose 13.5 hrs of observing time to conduct a deep search for radio pulsars around four candidate sdB+pulsar systems which are accessible with Parkes. A detection would (a) be the first time a pulsar bound to an sdB star has been detected, confirming the efficacy of the predicted binary-evolution channel; and (b) allow for an accurate estimate of the sdB mass, testing models for these enigmatic stars.