On the origin of field O-type stars

E. Schilbach; S. Roeser

doi:10.1051/0004-6361:200809936

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arXiv · 0806.0762

On the origin of field O-type stars

E. Schilbach·S. Roeser

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Abstract

Aims: We try 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 if 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 for back-tracing 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 Myrs. Only for 32 stars or about 9% of all O-stars from this catalogue, the question of their origin in groups is 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 Myrs 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 M_Sun per Myr. We prove that zeta Pup had its origin in the open cluster Trumpler 10 which it left about 2.5 Myrs 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 R_Sun, a mass of 22.5 M_Sun, and a luminosity of log L/L_Sun of 5.74) i.e, zeta 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.

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E. Schilbach, S. Roeser. 2008-06-04. On the origin of field O-type stars. https://doi.org/10.1051/0004-6361:200809936

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