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J.C. Martin (Case Western Reserve University)
Since the discovery of faint blue stars at high galactic latitudes, which spectroscopically appear to be similar to Population I B-stars, a debate has raged about their origin and characteristics. Their faint apparent magnitudes have been interpreted to place many of them several kiloparsecs above the disk in the galactic halo. Some have been thought to be too far from the disk and moving too slow to have had their origins in the star forming regions of the disk and to have been ejected to their present location. A sample of these stars, taken from the Hipparcos catalog, was observed at high spectroscopic dispersion (R=60000), analyzed for chemical composition, and traced back in time along their trajectory in the galactic potential using their full computed space velocities (determined from radial velocity and proper motions). The kinematics and chemical composition of a large fraction of the sample are consistent with their formation in, and ejection from, the star forming regions of the galactic disk. Another small but significant part of the sample show potential conflicts between their time of flight and main-sequence lifetime. Possible explanations for these stars are explored.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.