Volume 512, March-April 2010
|Number of page(s)||4|
|Published online||26 March 2010|
Letter to the Editor
The nature of B supergiants: clues from a steep drop in rotation rates at 22 000 K
The possibility of bi-stability braking
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland e-mail: email@example.com
2 Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
3 Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
4 Astronomical Institute Anton Pannekoek, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, The Netherlands
5 ESA, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Accepted: 4 March 2010
The location of B supergiants in the Hertzsprung-Russell diagram (HRD) represents a long-standing problem in massive star evolution. Here we propose their nature may be revealed utilising their rotational properties, and we highlight a steep drop in massive star rotation rates at an effective temperature of 22 000 K. We discuss two potential explanations for it. On the one hand, the feature might be due to the end of the main sequence, which could potentially constrain the core overshooting parameter. On the other hand, the feature might be the result of enhanced mass loss at the predicted location of the bi-stability jump. We term this effect “bi-stability braking” and discuss its potential consequences for the evolution of massive stars.
Key words: stars: rotation / stars: evolution / stars: early-type / stars: massive / stars: mass-loss / Hertzsprung Russell and C-M diagrams
© ESO, 2010
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