Polarization, single-pulse variability, and short-time-scale timing noise of seven millisecond pulsars

Using the Five-hundred-metre Aperture Spherical radio Telescope (FAST), we obtained high-quality polarization profiles for seven millisecond pulsars (MSPs). These include the first reported polarization profile for PSR J1933$+$1726, as well as the first determinations of Faraday rotation measures (RMs) for PSRs J1933$+$1726, J1932$+$1756, and J1914$+$0659. Single-pulse analysis of PSR J2053$+$4650 shows that the average profile, formed from bright pulses, exhibits weak bridge emission. Using Longitude-Resolved Fluctuation Spectrum analysis, we identified periodic intensity modulations in PSRs J2045$+$3633 and J2053$+$4650 for the first time. By decomposing the total white noise into its three principal components, namely radiometer noise, pulse jitter, and diffractive interstellar scintillation, we find that scintillation noise is negligible, contributing less than 10 per cent to the total white noise. The timing residuals of PSRs J2045$+$3633 and J2053$+$4650 are dominated by intrinsic pulse jitter, with σ J(1\, h) ≈ 297 ns and 116 ns, respectively, whereas the other pulsars are radiometer-noise-limited. For these two jitter-dominated pulsars, we further investigated the frequency dependence of jitter and identified contrasting behaviours. We demonstrated that matrix template matching using full Stokes parameters can effectively mitigate jitter noise.