First systematic study reporting the changes in eclipse cut-off frequency for pulsar J1544+4937

TL;DR

This study systematically investigates the temporal variations in eclipse cut-off frequency of pulsar J1544+4937 over a decade, revealing dynamic changes linked to the companion's mass loss rate and magnetic environment.

Contribution

It provides the first systematic analysis of eclipse cut-off frequency variations in pulsar J1544+4937 using long-term data from uGMRT, highlighting the influence of mass loss rate.

Findings

Significant variation in eclipse cut-off frequency from 343 MHz to >740 MHz.

Observed frequency changes on timescales of hours to months.

Correlation between eclipse cut-off frequency and companion's mass loss rate.

Abstract

We present results from a long-term monitoring of frequency dependent eclipses of the radio emission from PSR J1544+4937 which is a ``black widow spider'' millisecond pulsar (MSP) in a compact binary system. The majority of such systems often exhibit relatively long duration radio eclipses caused by ablated material from their companion stars. With the wide spectral bandwidth of upgraded Giant Metrewave Radio Telescope (uGMRT), we present first systematic study of temporal variation of eclipse cut-off frequency. With decade-long monitoring of 39 eclipses for PSR J1544+4937, we notice significant changes in the observed cut-off frequency ranging from 343 $\pm$ 7 MHz to > 740 MHz. We also monitored changes in eclipse cut-off frequency on timescales of tens of days and observed a maximum change of $\ge$ 315 MHz between observations that were separated by 22 days. In addition, we observed a change of $\sim$ 47 MHz in eclipse cut-off frequency between adjacent orbits, i.e. on timescales of $\sim 2.9$ hours. We infer that such changes in the eclipse cut-off frequency depict an eclipse environment for the PSR J1544+4937 system that is dynamically evolving, where, along with the change in electron density, the magnetic field could also be varying. We also report a significant correlation between the eclipse cut-off frequency and the mass loss rate of the companion. This study provides the first direct evidence of mass loss rate affecting the frequency dependent eclipsing in a spider MSP.