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

TL;DR

This paper investigates the magnetic and plasma environment of black widow millisecond pulsars using broadband polarization observations, revealing depolarization, eclipse cutoff frequencies, and magnetic field variations across multiple systems.

Contribution

It provides the first orbital phase-dependent polarization analysis of three BW MSPs with broadband data, expanding the sample size and understanding of eclipse mechanisms.

Findings

Depolarization observed during eclipses in all three MSPs.

Eclipse cutoff frequencies vary with orbital phase and time.

Synchrotron absorption identified as primary eclipse mechanism.

Abstract

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 ultra-wide-bandwidth low-frequency receiver (UWL) of the Parkes 'Murriyang' radio telescope is utilised for full polarisation observations covering frequencies from 704-4032 MHz. Depolarisation of pulsed emission is observed during the eclipse phase of three BW MSPs namely, J0024-7204J, J1431-4715 and PSR J1959+2048, consistent with previous studies of other BW MSPs. We estimated orbital phase dependent RM values for these MSPs. The wide bandwidth observations also provided the constraints on 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 $\pm$ 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 to the eclipse environment.