The Origins and Evolutionary Status of B Stars Found Far From the Galactic Plane I: Composition and Spectral Features

Abstract

The existence of faint blue stars far above the galactic plane, which have spectra that are similar to nearby Population I B stars, present several interesting questions. Among them are: Can a Population I B star travel from the disk to a position many kiloparsecs above the plane in a relatively short main sequence lifetime? Is it possible that single massive star formation is occurring far from the galactic plane? Are these objects something else masquerading as main sequence B stars? This paper (the first of two) analyzes the abundances of a sample of these stars and reveals several which are chemically similar to nearby Population I B stars while others clearly have abundance patterns more like those expected in BHB or PAGB stars. Several of those with old evolved star abundances also have interesting features of note in their spectra. We also consider why this sample does not have any classical Be stars and identify at least two nearby solar metallicity BHB stars.

arXiv comment43 pages; 13 figures; 14 tables; accepted for publication in AJ

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