Gamma-ray burst energy spectra: theoretical models,old and new |
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Authors: | Matthew G Baring |
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Institution: | (1) South African Astronomical Observatory, Observatory 7935, P.O. Box 9, Cape Town, South Africa |
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Abstract: | The M, S and C stars may be placed in an evolutionary sequence on the basis of direct observation of the spectroscopic transitions on the AGB of rich intermediate-age clusters in the Magellanic Clouds, but some S and C stars cannot be accounted for in this way. The S stars in Centauri owe their peculiarity to a primordial enrichment in s-process elements. The J-type (13C-rich) carbon stars originate in a different way to the ordinary cool N-type carbon stars. Some of them have silicate-rich circumstellar dust, contrary to expectation. Some of the carbon-rich RV Tauri stars also have silicate-rich dust and in both cases it may be organised in a disc. Observational evidence for gas and dust ejection by ordinary N-type carbon stars has been found and may be inferred for some RV Tauri stars. |
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Keywords: | Late-type Stars Evolution Carbon Stars RV Tauri Stars |
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