HD 167971 is a triple system consisting of a 3.3-day eclipsing binary (O5-8 V + O5-8 V) and an O8 supergiant. It is also a well known non-thermal radio emitter. We observed the radio emission of HD 167971 with the Very Large Array (VLA) and the …
We present a model for the non-thermal radio emission from presumably single O stars, in terms of synchrotron emission from relativistic electrons accelerated in wind-embedded shocks. These shocks are associated with an unstable, chaotic wind. The …
We present a model for the non-thermal radio emission from bright O stars, in terms of synchrotron emission from wind-embedded shocks. The model is an extension of an earlier one, with an improved treatment of the cooling of relativistic electrons. …
We present an efficient technique to study the 1D evolution of instability-generated structure in winds of hot stars out to very large distances (~1000 stellar radii). This technique makes use of our previous finding that external forces play little …
We discuss the results of two XMM-Newton observations of the open cluster NGC 6604 obtained in April and September 2002. We concentrate mainly on the multiple system HD 167971 (O5-8V + O5-8V + (O8I)). The soft part of the EPIC spectrum of this system …
We present a radio lightcurve of the O5.5 III(f^+) star HD 168112, based on archive data from the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). The fluxes show considerable variability and a negative spectral index, thereby …
We present a theoretical model for the non-thermal radio emission from single hot stars, in terms of synchrotron radiation from electrons accelerated in wind-embedded shocks. The model is described by five independent parameters each with a …
We present radio and submillimetre observations of the O4I(n)f star zeta Pup, and discuss structure in the outer region of its wind ( ~ 10-100 R_*). The properties of bremsstrahlung, the dominant emission process at these wavelengths, make it …
We present a new method to study the evolution of instability-generated structure in the outer winds of hot stars. We coin this method a pseudo-planar moving periodic box technique. It makes use of the fact that the outer evolution of structure can …
We report the results of a multi-wavelength investigation of the O4 V star 9 Sgr (= HD 164794). Our data include observations in the X-ray domain with XMM-Newton, in the radio domain with the VLA as well as optical spectroscopy. 9 Sgr is one of a few …