 |
 |
Astron. Astrophys. 359, 306-310 (2000)
Rotation and evolution of A stars: looking for progenitors of cool Ap stars
S. Hubrig 1,
P. North 2 and
A. Medici 1
1 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
2 Institut d'Astronomie de l'Université de Lausanne, 1290 Chavannes-des-bois, Switzerland
Received 22 March 2000 / Accepted 2 May 2000
Abstract
We explore to what extent the study of the projected rotational
velocities of normal A stars might reveal the existence of progenitors
of cool Ap stars, i.e. of slowly rotating normal young A stars. Since
according to a recent work, magnetic Ap stars with masses ranging from
1.7 to 2.5 ![[FORMULA]](img1.gif)
are never found on the
ZAMS in the HR diagram, but have completed at least 30% of their MS
lifetime, one may suspect that some normal young A stars will become
Ap later on. Such progenitors are expected to rotate slowly, as is the
case of magnetic Ap stars. We show that an unambiguous proof of their
existence would require a much larger sample than is available
today.
A sample of A stars with homogeneous determinations of
![[FORMULA]](img2.gif)
and with precise Hipparcos parallaxes
is examined. It is shown that no statistically significant difference
can be found between the
distributions of young and old stars, and that the data are compatible
with conservation of angular momentum in the case of rigid-body
rotation. The distribution of young A
stars is compatible with a Maxwellian distribution of equatorial
velocities, while this is less so of the older A stars.
Key words: stars: chemically
peculiar 
stars: rotation
stars: evolution
Send offprint requests to: S. Hubrig
This article contains no SIMBAD objects.
Contents
- 1. Introduction
- 2. The cost of looking for progenitors of Ap stars
- 3. Basic data
- 4. Analysis
- 5. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000
Online publication: June 30, 2000
helpdesk.link@springer.de