Chandra Detects the Rare Oxygen-type Wolf-Rayet Star WR 142 and OB Stars in Berkeley 87

TL;DR

This study reports the first X-ray detection of the rare oxygen-type Wolf-Rayet star WR 142 in Berkeley 87, revealing its extremely hard X-ray emission and contrasting it with other OB stars in the cluster.

Contribution

First X-ray observation of the rare WO-type Wolf-Rayet star WR 142, providing insights into its emission mechanisms and properties within a young star cluster.

Findings

WR 142 is a faint, extremely hard X-ray source.

Seven OB stars detected with varying X-ray properties.

WR 142's emission mechanism remains uncertain, possibly thermal or nonthermal.

Abstract

We present first results of a Chandra X-ray observation of the rare oxygen-type Wolf-Rayet star WR 142 (= Sand 5 = St 3) harbored in the young, heavily-obscured cluster Berkeley 87. Oxygen type WO stars are thought to be the most evolved of the WRs and progenitors of supernovae or gamma ray bursts. As part of an X-ray survey of supposedly single Wolf-Rayet stars, we observed WR 142 and the surrounding Berkeley 87 region with Chandra ACIS-I. We detect WR 142 as a faint, yet extremely hard X-ray source. Due to weak emission, its nature as a thermal or nonthermal emitter is unclear and thus we discuss several emission mechanisms. Additionally, we report seven detections and eight non-detections by Chandra of massive OB stars in Berkeley 87, two of which are bright yet soft X-ray sources whose spectra provide a dramatic contrast to the hard emission from WR 142.