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The Role of Rotation in the Evolution of Massive StarsRecent evolutionary models of massive stars predict important effects of rotation including: increasing the rate of mass-loss; lowering the effective gravity; altering the evolutionary track on the HRD; extending the main-sequence phase (both on the HR diagram and in time); and mixing of CNO-processed elements up to the stellar surface. Observations suggest that rotation is a more important factor at lower metallicities because of higher initial rotational velocities and weaker winds. This makes the SMC, a low-metallicity galaxy (Z= 0.2 solar Z), an excellent environment for discerning the role of rotation in massive stars. We report on a FUSE + STIS + optical spectral analysis of 17 O-type stars in the SMC, where we found an enormous range in N abundances. Three stars in the sample have the same (low) CN abundances as the nebular material out of which they formed, namely C = 0.085 solar C and N = 0.034 solar N. However, more than half show N approx. solar N, an enrichment factor of 30X! Such unexpectedly high levels of N have ramifications for the evolution of massive stars including precursors to supernovae. They also raise questions about the sources of nitrogen in the early universe.
Document ID
20040015293
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Heap, Sara R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Lanz, Thierry M.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2002
Subject Category
Astronomy
Meeting Information
Meeting: American Astronomical Association Meeting
Location: Seattle, WA
Country: United States
Start Date: January 5, 2003
End Date: January 9, 2003
Sponsors: American Astronomical Society
Funding Number(s)
CONTRACT_GRANT: FUSE-B134
CONTRACT_GRANT: GO-7437
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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