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Massive star evolution in the Small Magellanic Cloud

Published online by Cambridge University Press:  26 May 2016

Daniel J. Lennon*
Affiliation:
The Isaac Newton Group of Telescopes, Apartado de Correos 321, E-38700, Santa Cruz de La Palma, Canary Islands, España

Abstract

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We discuss abundances for eight early B-type giant/supergiant stars in the SMC cluster NGC 330. All are nitrogen rich with an abundance approximately 1.3 dex higher than an SMC main-sequence field. Given the number of B-type stars with low rotational projected velocities in NGC 330 (all our targets have v sin i < 50 kms–1), we suggest that it is unlikely that the stars in our sample are seen almost pole-on, but rather that they are intrinsically slow rotators. Comparing these results with the predictions of stellar evolution models including the effects of rotationally induced mixing, we conclude that while the abundance patterns may indeed be reproduced, those models with initially large rotational velocities do not reproduce the observed range of effective temperatures of our sample, nor the currently observed rotational velocities. Binary models may be able to produce stars in the observed temperature range and provide a promising alternative to single star models for explaining the observations. We also discuss the clear need for stellar evolution calculations employing the correct chemical mix of carbon, nitrogen and oxygen for the SMC.

Type
Part 2. Interiors of Massive Stars
Copyright
Copyright © Astronomical Society of the Pacific 2003 

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