An X-ray Survey of Wolf-Rayet Stars in the Magellanic Clouds. II. The ROSAT PSPC and HRI Datasets

TL;DR

This study surveys Wolf-Rayet stars in the Magellanic Clouds for X-ray emission using archival ROSAT data, finding a low detection rate compared to previous Chandra observations, highlighting the importance of high-resolution instruments.

Contribution

It provides the first systematic analysis of ROSAT data for WR stars in the Magellanic Clouds, comparing detection rates with Chandra results to emphasize instrument sensitivity differences.

Findings

X-ray emission detected in 7 out of 117 WR stars in ROSAT data.

Detection rate is lower than in Chandra surveys, underscoring the need for high-resolution observations.

Some WR stars detected by both ROSAT and Chandra show no significant long-term variability.

Abstract

Wolf-Rayet (WR) stars in the Magellanic Clouds (MCs) are ideal for studying the production of X-ray emission by their strong fast stellar winds. We have started a systematic survey for X-ray emission from WR stars in the MCs using archival Chandra, ROSAT, and XMM-Newton observations. In Paper I, we reported the detection of X-ray emission from 29 WR stars using Chandra ACIS observations of 70 WR stars in the MCs. In this paper, we report the search and analysis of archival ROSAT PSPC and HRI observations of WR stars. While useful ROSAT observations are available for 117 WR stars in the MCs, X-ray emission is detected from only 7 of them. The detection rate of X-ray emission from MCs WR stars in the ROSAT survey is much smaller than in the Chandra ACIS survey, illustrating the necessity of high angular resolution and sensitivity. LMC-WR 101-102 and 116 were detected by both ROSAT and Chandra, but no large long-term variations are evident.