Discovery of Variable Iron Fluorescence from Reflection Nebulae in the Galactic Center

Based on three years of deep observations of the Galactic center with theChandra X-ray Observatory, we report the discovery of changes in theintensities and morphologies of two hard X-ray nebulosities. The nebulositiesare dominated by fluorescent iron emission, and are coincident with molecularclouds. The morphological changes are manifest on parsec scales, which requiresthat these iron features are scattered X-rays from a 2 or 3-year-long outburstof a point source (either Sgr A* or an X-ray binary) with a luminosity of atleast 1e37 erg/s. The variability precludes the hypotheses that these nebulaeeither are produced by keV electrons bombarding molecular clouds, or areiron-rich ejecta from supernovae. Moreover, the morphologies of the reflectionnebulae implies that the dense regions of the clouds are filamentary, withwidths of ~0.3 pc and lengths of ~2 pc.Comment: 5 pages, 3 figures (2 color). submitted to ApJ