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

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 (~10^5 K) emitting material near the cold cloud.

11 pages, 4 figures

References in corpus (4)

• High Proper Motion Stars in the Vicinity of Sgr A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy
• Equivalent width, shape and proper motion of the iron fluorescent line emission from the molecular clouds as an indicator of the illuminating source X-ray flux history
• Hyperstrong Radio-Wave Scattering in the Galactic Center. II. A Likelihood Analysis of Free Electrons in the Galactic Center
• ASCA Observations of the Sgr B2 Cloud: An X-Ray Reflection Nebula

Cited by in corpus (8)

• X-ray Diagnostics of Giant Molecular Clouds in the Galactic Center Region and Past Activity of Sgr A*
• The X-ray Ridge Surrounding Sgr A* at the Galactic Center
• The Sgr B2 X-ray Echo of the Galactic Center Supernova Explosion that Produced Sgr A East
• The Cosmic Ray Distribution in Sagittarius B
• X-ray emission from the giant molecular clouds in the Galactic Center region and the discovery of new X-ray sources
• X-ray Polarization Signatures of Compton Scattering in Magnetic Cataclysmic Variables
• Diffusive Cosmic-ray Acceleration in Sagittarius A*
• On the Nature of the X-ray Emission from the Galactic Center Region