Silicate and hydrocarbon emission from Galactic M supergiants |
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Authors: | R J Sylvester C J Skinner & M J Barlow |
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Institution: | Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT,;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA |
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Abstract: | Following our discovery of unidentified infrared (UIR) band emission in a number of M supergiants in h and χ Per, we have obtained 10-μm spectra of a sample of 60 galactic M supergiants. Only three new sources, V1749 Cyg, UW Aql and IRC+40 427, appear to show the UIR bands; the others show the expected silicate emission or a featureless continuum. The occurrence of UIR-band emission in M supergiants is therefore much higher in the h and χ Per cluster than in the Galaxy as a whole. Possible explanations for the origin and distribution of UIR bands in oxygen-rich supergiants are discussed. We use our spectra to derive mass-loss rates ranging from 10?8 to 10?4 M⊙ yr?1 for the new sample, based on the power emitted in the silicate feature. The relationship between mass-loss rate and luminosity for M supergiants is discussed, and correlations are explored between their mid-infrared emission properties. |
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Keywords: | circumstellar matter stars: mass-loss supergiants open clusters and associations: individual: h and χ Per infrared: stars |
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