The Masses of the B Stars in the High Galactic Latitude Eclipsing Binary IT Librae

A number of blue stars which appear to be similar to Population I B-stars inthe star forming regions of the galactic disk are found more than 1 kpc fromthe galactic plane. Uncertainties about the true distances and masses of thesehigh latitude B-stars has fueled a debate as to their origin and evolutionarystatus. The eclipsing binary IT Lib is composed of two B-stars, isapproximately one kiloparsec above the galactic plane, and is moving backtoward the plane. Observations of the light and velocity curves presented herelead to the conclusion that the B-stars in this system are massive youngmain-sequence stars. While there are several possible explanations, it appearsmost plausible that the IT Lib system formed in the disk about 30 million yearsago and was ejected on a trajectory taking it to its present position.Comment: 26 pages, 3 figures, accepted for publication in the PASP (January 2003