Suzaku Observation of the Diffuse X-Ray Emission from the Open Cluster Westerlund 2: a Hypernova Remnant?

TL;DR

This study analyzes Suzaku X-ray observations of Westerlund 2, revealing thermal and non-thermal components, suggesting past supernova activity, and providing insights into particle acceleration and cooling processes in the cluster.

Contribution

First detailed Suzaku X-ray analysis of Westerlund 2 revealing multiple thermal components and implications for past supernova activity.

Findings

Diffuse X-ray emission consists of multiple thermal components.

Non-thermal X-ray flux is lower than TeV gamma-ray flux, indicating cooled electrons.

Gamma-ray emission likely from high-energy protons, not electrons.

Abstract

We present the analysis of Suzaku observations of the young open cluster Westerlund 2, which is filled with diffuse X-ray emission. We found that the emission consists of three thermal components or two thermal and one non-thermal components. The upper limit of the energy flux of the non-thermal component is smaller than that in the TeV band observed with H.E.S.S. This may indicate that active particle acceleration has stopped in this cluster, and that the accelerated electrons have already cooled. The gamma-ray emission observed with H.E.S.S. is likely to come from high-energy protons, which hardly cool in contrast with electrons. Metal abundances of the diffuse X-ray gas may indicate the explosion of a massive star in the past.