FAST Observations of the Microstructure in Interpulse Pulsars

In this study, we investigate the microstructure properties of four pulsars (PSRs J0953+0755 (B0950+08), J0627+0706, J0826+2637 (B0823+26) and J1946+1805 (B1944+17)) using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), with particular emphasis on identifying microstructure within interpulse (IP). Through the application of autocorrelation function (ACF) analysis and fast Fourier transform (FFT) techniques, we have systematically examined the periodicity of microstructure in these pulsars. Our findings represent the first successful detection of microstructure within IP. Furthermore, we conducted a comprehensive statistical analysis comparing the characteristic timescales ($\tau_{\mu}$) and the characteristic periods $P_{\mu}$ of quasi-periodic microstructure between the main pulse (MP) and IP, and our results indicate that the $\tau_{\mu}$ and $P_{\mu}$ of microstructure across components appear consistent within measurement errors for PSR J0627+0706, but microstructure in IP are relatively smaller than those in MP for PSR J0953+0755. Furthermore, the relationship between $P_{\mu}$ of microstructure and the rotation period in neutron star populations was reconfirmed: $P_{\mu}(\text{ms})=(1.337\pm0.114)\times P(\text{s})^{(1.063\pm0.038)}$.