Discovery of a one-sided radio filament of PSR J0538+2817 in S147: escape of relativistic PWN leptons into surrounding supernova remnant?

TL;DR

This paper reports the discovery of a unique one-sided radio filament near PSR J0538+2817, possibly indicating relativistic leptons escaping the pulsar wind nebula into the surrounding supernova remnant, challenging typical pulsar tail models.

Contribution

It presents the first observation of a one-sided radio filament ahead of a pulsar, suggesting a new type of pulsar-ISM interaction involving escaping relativistic particles.

Findings

Radio filament is aligned with pulsar proper motion

No X-ray or optical emission detected from the filament

Filament may connect pulsar wind nebula with ambient medium

Abstract

We report the discovery of a faint radio filament near PSR J0538+2817 in the NVSS, CGPS, and the Rapid ASKAP Continuum Survey data. This pulsar is plausibly associated with the supernova that gave rise to the Spaghetti Nebula (Simeis 147). The structure is one-sided and appears to be almost aligned (within 17 degrees) with the direction of the pulsar's proper motion, but in contrast to the known cases of pulsar radio tails, it is located ahead of the pulsar. At the same time, this direction is also approximately (within 5 degrees) perpendicular to the axis of the extended non-thermal X-ray emission around the pulsar. No X-ray or optical emission is detected from the filament region, although the end point of the radio filament appears to be adjacent to a filament of H$_\alpha$ emission. We speculate that this structure might represent a filament connecting pulsar wind nebula with the ambient interstellar medium filled with relativistic electrons escaping the pulsar nebula, i.e. a radio analogue of X-ray filaments of Guitar and Lighthouse PWNs and filaments of non-thermal radio emission in the Galactic Center.