Low-radio-frequency eclipses of the redback pulsar J2215+5135 observed in the image plane with LOFAR

TL;DR

This study demonstrates that redback pulsar eclipses can be detected in low-frequency radio images, revealing frequency-dependent eclipse durations and offering new methods for pulsar detection in wide-field surveys.

Contribution

First detection of redback pulsar eclipses in interferometric images at low frequencies, showing frequency dependence and highlighting imaging surveys' potential for pulsar studies.

Findings

Eclipse duration scales with frequency as approximately ν^{-0.4}

Eclipses are caused by an absorbing medium, not scattering

Imaging data can detect pulsar eclipses, expanding detection methods

Abstract

The eclipses of certain types of binary millisecond pulsars (i.e. `black widows' and `redbacks') are often studied using high-time-resolution, `beamformed' radio observations. However, they may also be detected in images generated from interferometric data. As part of a larger imaging project to characterize the variable and transient sky at radio frequencies <200 MHz, we have blindly detected the redback system PSR J2215+5135 as a variable source of interest with the Low-Frequency Array (LOFAR). Using observations with cadences of 2 weeks - 6 months, we find preliminary evidence that the eclipse duration is frequency dependent ($\propto \nu^{-0.4}$), such that the pulsar is eclipsed for longer at lower frequencies, in broad agreement with beamformed studies of other similar sources. Furthermore, the detection of the eclipses in imaging data suggests an eclipsing medium that absorbs the pulsed emission, rather than scattering it. Our study is also a demonstration of the prospects of finding pulsars in wide-field imaging surveys with the current generation of low-frequency radio telescopes.