The Expansion and Radio Spectral Index of G21.5-0.9: Is PSR J1833-1034 the Youngest Pulsar?

TL;DR

This study presents high-resolution radio observations of G21.5-0.9, revealing its expansion rate and spectral properties, and suggests that PSR J1833-1034 is among the youngest pulsars in the Galaxy.

Contribution

It provides new 5-GHz VLA radio images and measures the remnant's expansion, estimating its age and proposing PSR J1833-1034 as potentially the youngest pulsar.

Findings

Expansion speed of 910 +/- 160 km/s

Estimated remnant age of 870 (+200,-150) years

Identification of filamentary and torus-like structures

Abstract

We report on new 5-GHz VLA radio observations of the pulsar-powered supernova remnant G21.5-0.9. These observations have allowed us to make a high-quality radio image of this remnant with a resolution of ~0.7". It has a filamentary structure similar to that seen in the Crab Nebula. Radio structure suggestive of the torus seen around the Crab pulsar is tentatively identified. We also compared the new image with one taken ~15 yr earlier at 1.5 GHz, both to find the expansion speed of the remnant and to make a spectral index image. Between 1991 and 2006, we find that the average expansion rate of the remnant is 0.11 +/- 0.02 %/year, corresponding, for a distance of 5 kpc, to a speed of 910 +/- 160 km/s wrt. the centre of the nebula. Assuming undecelerated expansion, this expansion speed implies that the age of G21.5-0.9 is 870 (+200,-150) yr, which makes PSR J1833-1034 one of the youngest, if not the youngest, known pulsars in the Galaxy.