Long-term soft and hard X-ray investigation of the colliding wind WN+O binary WR 25

Abstract

We investigated the long-term behaviour in X-rays of the colliding wind binary WR 25, using archival data obtained with Suzaku, Swift, XMM-Newton, and NuSTAR spanning over ~16 years. Our analysis reveals phase-locked variations repeating consistently over many consecutive orbits, in agreement with an X-ray emission fully explained by thermal emission from the colliding winds in the 208-d orbit. We report on a significant deviation of the X-ray flux with respect to the 1/D trend (expected for adiabatic shocked winds) close to periastron passage. The absence of a drop in post-shock plasma temperature close to periastron suggests this break in trend cannot be explained in terms of reduced pre-shock velocities in this part of the orbit. Finally, NuSTAR data reveal a lack of hard X-ray emission (above 10.0 keV) above the background level. Upper limits on a putative non-thermal emission strongly suggest that the sensitivity of present hard X-ray observatories is not sufficient to detect non-thermal emission from massive binaries above 10 keV, unless the wind kinetic power is large enough to significantly feed particle acceleration in the wind-wind interaction.

15 Pages, 12 Figures, 6 Tables, Accepted for the publication in MNRAS

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• Physical Properties of Wolf-Rayet Stars
• Mass loss from hot massive stars
• Non-thermal emission processes in massive binaries
• Hard X-ray emission from Eta Carinae
• Non-thermal X-rays from Colliding Wind Shock Acceleration in the Massive Binary Eta Carinae
• Phase-resolved XMM-Newton and swift observations of WR 25
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• Quest for the upcoming periastron passage of an episodic dust maker and particle accelerating colliding wind binary: WR 125
• LIFELINE: The program for the simulation of the X-ray line profiles in massive colliding wind binaries
• Radio study of the colliding wind binary HD93129A near periastron and its surroundings
• Investigation of the nature of the wind interaction in HD93205 based on multi-epoch X-ray observations
• Multiwavelength view of massive binaries