GMRT discovery of PSR J1544+4937, an eclipsing black-widow pulsar identified with a Fermi LAT source

TL;DR

This paper reports the discovery of an eclipsing black-widow millisecond pulsar, PSR J1544+4937, identified through deep GMRT radio observations and confirmed as a gamma-ray source via Fermi LAT data, revealing complex eclipse behavior.

Contribution

First detection of an eclipsing black-widow pulsar associated with an un-cataloged Fermi gamma-ray source using GMRT observations.

Findings

Pulsar has a 2.16 ms spin period and a 2.9-hour orbit.

Eclipses occur at 322 MHz but not at 607 MHz, showing frequency-dependent eclipsing.

Eclipse ingress varies, indicating a clumpy, dynamic eclipsing medium.

Abstract

Using the Giant Metrewave Radio Telescope (GMRT) we performed deep observations to search for radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) gamma-ray sources. We report the discovery of an eclipsing black-widow millisecond pulsar, PSR J1544+4937, identified with the un-cataloged gamma-ray source Fermi J1544.2+4941. This 2.16 ms pulsar is in a 2.9 hours compact circular orbit with a very low-mass companion (Mc > 0.017 Msun). At 322 MHz this pulsar is found to be eclipsing for 13% of its orbit, whereas at 607 MHz the pulsar is detected throughout the low-frequency eclipse phase. Variations in the eclipse ingress phase are observed, indicating a clumpy and variable eclipsing medium. Moreover, additional short-duration absorption events are observed around the eclipse boundaries. Using the radio timing ephemeris we were able to detect gamma-ray pulsations from this pulsar, confirming it as the source powering the gamma-ray emission.