X-rays from the episodic dust maker WR 137

TL;DR

This study analyzes X-ray data from WR 137, showing a two-temperature plasma spectrum and highlighting discrepancies with colliding stellar wind models, suggesting a need to revise the star's mass loss estimates.

Contribution

First detailed X-ray spectral analysis of WR 137 revealing plasma properties and challenges to existing stellar wind models.

Findings

X-ray spectrum fits a two-temperature plasma model

Colliding stellar wind models overestimate observed flux

Mass loss rate of WR 137 likely lower than previously thought

Abstract

We present an analysis of the XMM-Newton observation of the episodic dust maker WR 137. Global spectral fits show that its X-ray spectrum is well matched by a two-temperature optically-thin plasma emission (kT_1 ~ 0.4 keV and kT_2 ~ 2.2 keV). If we adopt the colliding stellar wind (CSW) picture for this wide WR+O binary, the theoretical CSW spectra match well the shape of the observed X-ray spectrum of WR 137 but they overestimate the observed flux (emission measure) by about two orders of magnitude. To reconcile the model predictions with observations, the mass loss of \WR must be reduced considerably (by about an order of magnitude) with respect to its currently accepted value. In all the spectral fits, the derived X-ray absorption is consistent with the optical extinction to WR 137.