X-rays from the episodic dust maker WR 137

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 (kT₁ ∼ 0.4 keV and kT₂ ∼ 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 137 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.