A Monte Carlo Study of the 6.4 keV Emission at the Galactic Center

Michael J. Fromerth(1,3), Fulvio Melia(2,4)


(1) Department of Physics, The University of Arizona, Tucson, AZ 85721
(2) Department of Physics and Steward Observatory, The University of Arizona, Tucson, AZ 85721
(3) NSF Graduate Fellow.
(4) Sir Thomas Lyle Fellow and Miegunyah Fellow.

Paper: submitted

EPrint Server: astro-ph/0008393


Abstract:

Strong fluorescent Fe line emission at 6.4 keV has been observed from the Sgr B2 giant molecular cloud located in the Galactic Center region. The large equivalent width of this line and the lack of an apparent illuminating nearby object indicate that a time-dependent source, currently in a low-activity state, is causing the fluorescent emission. It has been suggested that this illuminator is the massive black hole candidate, Sgr A*, whose X-ray luminosity has declined by an unprecedented six orders of magnitude over the past 300 years. We here report the results of our Monte Carlo simulations for producing this line under a variety of source configurations and characteristics. These indicate that the source may in fact be embedded within Sgr B2, although external sources give a slightly better fit to the data. The weakened distinction between the internal and external illuminators is due in part to the instrument response function, which accounts for an enhanced equivalent width of the line by folding some of the continuum radiation in with the intrinsic line intensity. We also point out that although the spectrum may be largely produced by K alpha emission in cold gas, there is some evidence in the data to suggest the presence of warm ( 105 K) emitting material near the cold cloud.


Preprints available from the authors at fromerth@physics.arizona.edu , or the raw TeX (no figures) if you click here.

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