Small-scale inhomogeneities and their impact on observed mass-loss rates of radiation-driven winds

• Applicant: Privatdozent Dr. Joachim Puls
• Subject Area: Astrophysics and Astronomy
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 179960930

• Final Report Year: 2015

Final Report Abstract

The project has accomplished its main task, namely to develop new models for quantitative spectroscopic analysis of hot stars with winds, accounting properly for the effects of a clumped wind consisting of a mixture of optically thick and thin clumps, and with a non-monotonic velocity field. A novel ’effective opacity’ method for line and continuum radiative transfer through a clumpy, accelerating medium was developed and presented in Sundqvist. This method has now been fully incorporated into our group’s model atmosphere and wind computer code fastwind. In the following years, we expect this new version of fastwind to be broadly applied by the research-community for spectroscopic studies of massive stars. First multi-wavelength studies (ranging from high-energy X-rays to the infrared domain) have been performed by us, suggesting that current Galactic O-star mass-loss rates included in models of massive star evolution are overestimated by a factor of ∼3. Inspired by this, we have already launched follow-up studies to this DFG project that will i) develop a new generation of theoretical wind models aiming to explain this reduction, and ii) compute new stellar evolution models using the lower rates.

Publications

• 2013: ”Constraints on Porosity and Mass Loss in O-star Winds from the Modeling of X-Ray Emission Line Profile Shapes”, ApJ, 770, 80
  Leutenegger M.A., Cohen D.H., Sundqvist J.O., Owocki S.P.
  
• 2013: ”The rotation rates of massive stars. How slow are the slow ones?, A&A, 559, L10
  Sundqvist J.O., Simon-Diaz S., Puls J., Markova N.
  
• 2014: ”Mass loss from inhomogeneous hot star winds III. An effective-opacity formalism for line radiative transfer in accelerating, clumped two-component media, and first results on theory and diagnostic”, A&A, 568, 59
  Sundqvist J.O., Puls. J., Owocki S.P.
  
• 2014: ”Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive”, MNRAS, 439, 908
  Cohen D.H., Wollman, E.E., Leutenegger, M.A., Sundqvist J.O., Fullerton A.W., Zsargo, J., Owocki, S.P.