The Slow X-Ray Expansion of the Northwestern Rim of the Supernova Remnant RX J0852.0-4622

TL;DR

This study measures the slow X-ray expansion of the supernova remnant RX J0852.0-4622, indicating it is older than previously thought, with an estimated age of 1,700-4,300 years and a distance of about 750 parsecs.

Contribution

The paper provides the first direct measurement of the remnant's expansion rate, challenging the assumption that it is a young supernova remnant and refining its age and distance estimates.

Findings

Expansion rate is about 0.023% over 6.5 years.

Estimated age of the remnant is 1,700-4,300 years.

Distance to the remnant is approximately 750 parsecs.

Abstract

The detection of radioactive decay line of 44Ti provides a unique evidence that the gamma-ray source is a young (< 1,000 yr) supernova remnant because of its short lifetime of about 90 yr. Only two Galactic remnants, Cassiopeia A and RX J0852.0-4622, are hitherto reported to be the 44Ti line emitter, although the detection from the latter has been debated. Here we report on an expansion measurement of the northwestern rim of RX J0852.0-4622 obtained with X-ray observations separated by 6.5 yr. The expansion rate is derived to be 0.023+/-0.006% that is about five times lower than those of young historical remnants. Such a slow expansion suggests that RX J0852.0-4622 is not a young remnant as has been expected. We estimate the age of 1,700-4,300 yr of this remnant depending on its evolutionary stage. Assuming a high shock speed of about 3000 km/sec, which is suggested by the detection of non-thermal X-ray radiation, the distance of about 750 pc to this remnant is also derived.