Issue |
A&A
Volume 489, Number 1, October I 2008
|
|
---|---|---|
Page(s) | 105 - 114 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:200809936 | |
Published online | 01 July 2008 |
On the origin of field O-type stars
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany e-mail: [elena;roeser]@ari.uni-heidelberg.de
Received:
9
April
2008
Accepted:
30
May
2008
Aims. We aim to identify the origins of field O-stars in the nearest 2 to 3 kpc around the Sun using the best presently available kinematic data on O-stars and on young open clusters. We investigate the question of whether the present-day data are consistent with the assumption that O-stars have formed in groups (clusters, associations), or in isolation.
Methods. We apply the epicycle theory to back-trace the orbits of O-type stars and of candidate parent open clusters.
Results. From the 370 O-stars in the “Galactic O star catalog v 2.0” (GOSV2) we have
investigated 93 stars classified as field, and found the origin for 73
of them in 48 open clusters younger than 30 Myr. Only for 32 stars or
about 9% of all O-stars from this catalogue is the question of their origin
in groups not solved; some of them may have originated in isolation or
may have disintegrated the group in which they formed.
Fifty percent of the young open clusters (age < 30 Myr)
in the “Catalogue of Open Cluster Data” (COCD) have O-stars
as members, or have ejected at least one O-star in the first 10 Myr of
their life, or both. During this period the average mass loss from open
clusters by ejecting O-stars is found to be 3 to 5 per Myr.
We prove that ζ Pup had its origin in the open cluster Trumpler 10 which
it left about 2.5 Myr ago, and that its present-day distance is
300 pc (compared to 440 pc before). The revised distance implies a
significant revision of the stellar parameters (a radius of 14
,
a mass of 22.5
, and a luminosity of log
of 5.74) i.e.,
ζ Pup is closer, less massive, and less luminous than previously thought.
Our findings provide independent estimates of the present-day distances
and absolute magnitudes of field O-stars.
Key words: stars: early-type / stars: formation / open clusters and associations: general
© ESO, 2008
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