Simulated low-intensity optical pulsar observation with single-photon detector

Context. Optical radiation of pulsars offers valuable clues to the physics of neutron stars, which are our only probes of the most extreme states of matter in the present-day universe. Still, only about 1% of all cataloged pulsars have known optical counterparts. Aims. The goal of this work is to develop an observational method optimized for discovering faint optical pulsars. Methods. A single-photon detector transforms the signal received by the telescope into a pulse sequence. The events obtained are time tagged and transformed into a histogram of event time differences. The histogram envelope presents the autocorrelation of the recorded optical signal and thus displays any periodicity of the input signal. Results. Simulations show that faint pulsars radiating in the optical regime can be detected in a straightforward way. As an example, a fictitious pulsar with a V-magnitude of 24.6 mag and a signature like the Crab pulsar can be discovered within one minute using an 8-m class telescope. At the detector’s peak sensitivity the average optical flux density would then amount to Fν = 0.63 μJy. With a 40-m class telescope, such as the forthcoming European ELT, the detection of optical pulsars with magnitudes V < 30 mag is within reach for a measurement time of one minute. A two-hour “blind search” with the ELT could reach V ∼ 31.3 mag. Conclusions. This method allows detecting faint periodic optical radiation with simple equipment and easy signal processing.