Unveiling frequency-dependent eclipsing in spider millisecond pulsars using broadband polarization observations with the Parkes

This study presents an orbital-phase-dependent analysis of three black widow spider millisecond pulsars (BW MSPs), aiming to investigate the magnetic field within the eclipse environment. The ultrawide-bandwidth low-frequency receiver of the Parkes Murriyang radio telescope is utilized for full polarization observations covering frequencies from 704−4032 MHz. Depolarization of pulsed emission is observed during the eclipse phase of three BW MSPs, namely PSR J0024−7204J, PSR J1431−4715, and PSR J1959+2048, consistent with previous studies of other BW MSPs. We estimated orbital-phase-dependent rotation measure values for these MSPs. The wide bandwidth observations also provided constraints on the eclipse cutoff frequency for these BW MSPs. For PSR J0024−7204J, we report temporal variation of the eclipse cutoff frequency coupled with changes in the electron column density within the eclipse medium across six observed eclipses. Moreover, the eclipse cutoff frequency for PSR J1431−4715 is determined to be 1251 ± 80 MHz, leading to the conclusion that synchrotron absorption is the primary mechanism responsible for the eclipsing. Additionally, for PSR J1959+2048, the estimated cutoff frequency exceeded 1400 MHz, consistent with previous studies. With this investigation, we have doubled the sample size of BW MSPs with orbital-phase-resolved studies, allowing a better probe of the eclipse environment.