| Issue |
A&A
Volume 378, Number 3, November II 2001
|
|
|---|---|---|
| Page(s) | 907 - 917 | |
| Section | Interstellar and circumstellar matter | |
| DOI | https://doi.org/10.1051/0004-6361:20011246 | |
| Published online | 15 November 2001 | |
Early type stars at high galactic latitudes*,**,***
I. Ten young massive B-type stars
Dr.-Remeis-Sternwarte, Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany
Corresponding author: M. Ramspeck, ramspeck@sternwarte.uni-erlangen.de
Received:
4
July
2001
Accepted:
3
September
2001
We present the results of quantitative spectral analyses of ten
apparently normal B-type stars. These stars were found to be young massive
B-type stars at distances of 
to 7.6 kpc from the galactic plane based on
their positions
in the (
, 
) diagram, normal abundance patterns and/or large projected
rotational velocities. We discuss formation scenarios (runaway star
scenarios versus a scenario for star formation in the halo) by comparing
times-of-flight and evolutionary time scales.
For all stars (except SB 357 and HS 1914+7139) both the scales are similar
indicating that the stars could have
formed in the galactic disk and been ejected from there soon after
their birth.
Derived ejection velocities range from 130 km s-1 to 440 km s-1 and
may be used to constrain models for ejection mechanisms.
Using new proper motion measurements we show that PHL 346,
which was considered the most likely candidate for a young B-type star born in
the halo, can be explained as a runaway star from the galactic plane.
Key words: Galaxy: halo / stars: early-type / stars: abundances / stars: kinematics / stars: evolution
Based on observations obtained at the W. M. Keck Observatory, which is operated by the Californian Association for Research in Astronomy for the California Institute of Technology and the University of California.
© ESO, 2001
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