Search for Interpulses in a Complete Sample of Pulsars at a Frequency of 111 MHz

Abstract

An interpulse search has been carried out in a sample of 96 pulsars observed on the Large Phased Array (LPA) radio telescope in the Pushchino Multibeams Pulsar Search (PUMPS). The pulsar sample has been complete for pulsars having a signal-to-noise ratio (\(S{\text{/}}N\)) in the main pulse (MP) greater than 40. To search for weak interpulses (IP), the addition of average profiles over an interval of up to 10 years has been used. Interpulses have been detected in 12 pulsars (12.5% of the sample), of which 7 pulsars have an interpulse located near the \(180^\circ \) phase relative to the main pulse (probable orthogonal rotators), and 5 have had phases far from \(180^\circ \) (probable coaxial rotators). The amplitude ratios of IP/MP have been in the range of 0.004‒0.023, the median value is 0.01. Estimates of the observed number of coaxial and orthogonal rotators with IP/MP of \({\kern 1pt} \geqslant {\kern 1pt} 0.01\) have not contradicted the model according to which, during evolution, the magnetic axis and the rotation axis become orthogonal.