Global modelling of X-ray spectra produced in O-type star winds

Abstract

High-resolution X-ray spectra of O-type stars revealed less wind absorption than expected from smooth winds with conventional mass-loss rates. Various solutions have been proposed, including porous winds, optically thick clumps or an overall reduction of the mass-loss rates. The latter has a strong impact on the evolution of the star. Our final goal is to analyse high resolution X-ray spectra of O-type stars with a multi temperature plasma model in order to determine crucial wind parameters such as the mass loss rate, the CNO abundances and the X-ray temperature plasma distribution in the wind. In this context we are developing a modelling tool to calculate synthetic X-ray spectra. We present, here, the main ingredients and physics necessary for a such work. Our code uses the AtomDB emissivities to compute the intrinsic emissivity of the hot plasma as well as the CMFGEN model atmosphere code to evaluate the opacity of the cool wind. Following the comparison between two formalisms of stellar wind fragmentation, we introduce, for the first time in X-rays, the effects of a tenuous inter-clump medium. We then explore the quantitative impact of different model parameters on the X-ray spectra such as the position in the wind of the X-ray emitting plasma. For the first time, we show that the two formalisms of stellar wind fragmentation yield different results, although the differences for individual lines are small and can probably not be tested with the current generation of X-ray telescopes. As an illustration of our method, we compare various synthetic line profiles to the observed O VIII λ 18.97Å line in the spectrum of ζ Puppis. We illustrate how different combinations of parameters can actually lead to the same morphology of a single line, underlining the need to analyse the whole spectrum in a consistent way when attempting to constrain the parameters of the wind.

accepted for publication in ApJ

References in corpus (6)

• X-Ray Spectroscopy of Stars
• The Effect of Porosity on X-ray Emission Line Profiles from Hot-Star Winds
• High resolution X-ray spectroscopy of bright O type stars
• X-Rays From Massive OB Stars: Thermal Emission From Radiative Shocks
• On the Importance of the Interclump Medium for Superionization: O VI Formation in the Wind of Zeta Pup
• Modeling broadband X-ray absorption of massive star winds

Cited by in corpus (14)

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• Thin-shell mixing in radiative wind-shocks and the Lx-Lbol scaling of O-star X-rays
• A detailed X-ray investigation of zeta Puppis - The variability on short and long timescales
• A spectroscopic investigation of the O-type star population in four Cygnus OB associations. II. Determination of the fundamental parameters
• Simultaneous X-ray and optical spectroscopy of the Oef supergiant lambda Cep
• A detailed X-ray investigation of ζ Puppis III. A spectral analysis of the whole RGS spectrum
• Measuring the shock-heating rate in the winds of O stars using X-ray line spectra
• The XMM-Newton EPIC X-ray Light Curve Analysis of WR 6
• Probing Wolf-Rayet Winds: Chandra/HETG X-Ray Spectra of WR 6
• X-ray diagnostics of massive star winds
• Modeling X-ray Emission Line Profiles from Massive Star Winds - A Review
• X-ray emission of massive stars and their winds
• Moving inhomogeneous envelopes of stars
• LIFELINE: The program for the simulation of the X-ray line profiles in massive colliding wind binaries