Magneto-active environments in pulsar binaries with the MeerKAT telescope: I. Pulsar sample and their basic properties

ABSTRACT

Eclipsing pulsar binaries and binaries with a high-mass companion are ideal systems for studying and understanding the properties of plasma in magneto-ionic environments. In this work, the first paper of a series, we present MeerKAT observations of three pulsar binaries: the high-mass binary PSR J1740–3052, the black widow PSR J2051–0827, and the redback PSR J1748–2446A (Terzan 5A). With the help of MeerKAT’s high-sensitivity polarimetric observations, we characterize the properties of these sources, including the linear/circular polarization, dispersion measure (DM), rotation measure (RM), and scattering time. The two eclipsing millisecond pulsars (PSR J2051–0827 and PSR J1748–2446A) exhibit strong orbital-phase-dependent propagation effects and we observe $\sim$2 eclipses in these systems during our observations. PSR J1740–3052 is a binary system with a 231 d orbital period. The relatively large separation results in a smooth RM variation, enabling us to resolve its variation time-scale and constrain the small-scale magnetic structure. A gradual RM variation is observed over $\sim$1500 s, occurring near periastron. This behaviour implies a magnetic spatial scale of $\sim$0.003 au in the companion wind, assuming a relative velocity of $\sim$250 km s$^{-1}$. The linear polarization intensity profiles of PSR J2051–0827 show shape variations as a function of frequency, with a stronger leading component emerging at lower frequencies. We observe signatures of the propagation effect in the polarization properties of PSR J1748–2446A during eclipse ingress and egress. These could arise from Faraday conversion or multipath propagation of the pulsar signal and requires detailed analysis.