Observational overview of clumping in hot stellar winds

  • In the old days (pre ∼1990) hot stellar winds were assumed to be smooth, which made life fairly easy and bothered no one. Then after suspicious behaviour had been revealed, e.g. stochastic temporal variability in broadband polarimetry of single hot stars, it took the emerging CCD technology developed in the preceding decades (∼1970-80’s) to reveal that these winds were far from smooth. It was mainly high-S/N, time-dependent spectroscopy of strong optical recombination emission lines in WR, and also a few OB and other stars with strong hot winds, that indicated all hot stellar winds likely to be pervaded by thousands of multiscale (compressible supersonic turbulent?) structures, whose driver is probably some kind of radiative instability. Quantitative estimates of clumping-independent mass-loss rates came from various fronts, mainly dependent directly on density (e.g. electron-scattering wings of emission lines, UV spectroscopy of weak resonance lines, and binary-star properties including orbital-period changes, electron-scattering, anIn the old days (pre ∼1990) hot stellar winds were assumed to be smooth, which made life fairly easy and bothered no one. Then after suspicious behaviour had been revealed, e.g. stochastic temporal variability in broadband polarimetry of single hot stars, it took the emerging CCD technology developed in the preceding decades (∼1970-80’s) to reveal that these winds were far from smooth. It was mainly high-S/N, time-dependent spectroscopy of strong optical recombination emission lines in WR, and also a few OB and other stars with strong hot winds, that indicated all hot stellar winds likely to be pervaded by thousands of multiscale (compressible supersonic turbulent?) structures, whose driver is probably some kind of radiative instability. Quantitative estimates of clumping-independent mass-loss rates came from various fronts, mainly dependent directly on density (e.g. electron-scattering wings of emission lines, UV spectroscopy of weak resonance lines, and binary-star properties including orbital-period changes, electron-scattering, and X-ray fluxes from colliding winds) rather than the more common, easier-to-obtain but clumping-dependent density-squared diagnostics (e.g. free-free emission in the IR/radio and recombination lines, of which the favourite has always been Hα). Many big questions still remain, such as: What do the clumps really look like? Do clumping properties change as one recedes from the mother star? Is clumping universal? Does the relative clumping correction depend on $\dot{M}$ itself?show moreshow less

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Metadaten
Author:Anthony F. J. Moffat
URN:urn:nbn:de:kobv:517-opus-17633
Document Type:Conference Proceeding
Language:English
Date of Publication (online):2008/04/25
Year of Completion:2007
Publishing Institution:Universität Potsdam
Release Date:2008/04/25
RVK - Regensburg Classification:US 1999.07
Organizational units:Extern / Extern
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 52 Astronomie / 520 Astronomie und zugeordnete Wissenschaften
Collections:Universität Potsdam / Tagungen / Clumping in hot-star winds: International Workshop, Potsdam, Germany, 18. - 22. June 2007
Universität Potsdam / Tagungen / Clumping in hot-star winds: International Workshop, Potsdam, Germany, 18. - 22. June 2007 / Talks and Discussions (in alphabetical order)
Universität Potsdam / Tagungen / Clumping in hot-star winds: International Workshop, Potsdam, Germany, 18. - 22. June 2007 / Talks and Discussions (organized by sections) / Spectroscopy and mass loss diagnostic: observations
Licence (German):License LogoKeine Nutzungslizenz vergeben - es gilt das deutsche Urheberrecht
Notes extern:
The complete edition of the proceedings "Clumping in hot-star winds" is available:
urn:nbn:de:kobv:517-opus-13981