ABSTRACT

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ABSTRACT: A recent sensitive survey has doubled the number of OH/IR stars known in the Galactic center (GC). The distribution of expansion velocities of the circumstellar shells of these stars shows an unexpectedly narrow peak at the high end tail. From this, we conclude that this sample of stars has a higher metallicity than any other sample known, and that a large fraction of stars has formed in an epoch of enhanced star formation at least one Giga-year ago. Thus one can distinguish three different groups of stars in the direction of the GC: an old bulge-like population, a group of relatively young stars formed from continously infalling gas, and a shrinking population of low-mass stars that formed in an isolated era - probably a starburst. This is a striking conclusion that can only be drawn from OH/IR stars, because they form the only tracable population older than a few hundred million years in the GC.