| Abstract : | Pulsars are usually detected by their narrow pulses or periodicity in time domain data. Typically, pulsar surveys use wider incoherent beams to map large areas of the sky, but the incoherent beam is less sensitive compared to regular imaging data. Separately, time-domain searches for pulsars are computationally expensive due to very large parameter space, and their detection sensitivity is affected by dispersion smearing, scattering, and rapid orbital motion of pulsars in binaries. The radio continuum images do not suffer from the limitations of time-domain searches, and therefore are equally sensitive to all pulsars, and allow us to find hard to detect pulsars, such as sub-millisecond pulsars, pulsar-black hole systems, and pulsars near the Galactic Centre. Building on a variance imaging technique proposed by Dai et al (2016), we have developed a new technique that detects pulsar candidates in radio images by measuring their scintillation bandwidth and timescale from the autocorrelation of dynamic spectra of sources. We use existing observations of PSR B1508+55 and its neighbouring sources as a test case for our technique. We demonstrate a method that extracts the dynamic spectrum of the pulsar and its neighbouring point sources by phasing and adding visibilities and show that the extracted dynamical spectrum is equivalent to that extracted from the GMRT phased-array beam and the full imaging pipeline. Our method of visibility phasing works 1000 times faster than the full imaging pipeline and allows us to rapidly identify possible pulsar candidates. |
