Time Variability of the Neutral Iron Lines from the Sgr B2 Region and its Implication of a Past Outburst of Sgr A*
Publication date: 16 April 2008
Authors: Inui, T. et al.
Journal: Accepted for publication in: Publications of the Astronomical Society of Japan
Year: 2008
Copyright: Astronomical Society of Japan
We investigate long-term X-ray behaviors from the Sgr B2 complex using archival data of the X-ray satellites Suzaku, XMM-Newton, Chandra and ASCA. The observed region of the Sgr B2 complex includes two prominent spots in the Fe I K-alpha line at 6.40 keV, a giant molecular cloud M0.66-0.02 known as the "Sgr B2 cloud" and an unusual X-ray source G0.570-0.018. Although these 6.40 keV spots have spatial extensions of a few pc scale, the morphology and flux of the 6.40 keV line has been time variable for 10 years, in contrast to the constant flux of the Fe XXV K-alpha line at 6.67 keV in the Galactic diffuse X-ray emission. This time variation is mostly due to M0.66-0.02; the 6.40 keV line flux declined in 2001 and decreased to 60% in the time span 1994-2005. The other spot G0.570-0.018 is found to be conspicuous only in the Chandra observation in 2000. From the long-term time variability (~10 years) of the Sgr B2 complex, we infer that the Galactic Center black hole Sgr A* was X-ray bright in the past 300 year and exhibited a time variability with a period of a few years.
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