1. High Energy Sky with Advancing Technology The Galactic Center View From Tenma--Suzaku Hakucho (1979)96 kg Tenma (1983) 216kg Ginga （ 1987 ） 420 kg ASCA （ 1993 ） 417 kg Suzaku (2005) 1600 kg

2. Si S Fe Tenma: Gas Scintilation Proportional Counter (2 times better resolution) We found Kα lines from highly ionized Fe, S and Si in the Galactic Ridge  Presence of High temperature plasma 6.7 keV line

3. Ginga (large proportional counter) surveyed the Glactic Plane with the 6.7 keV and continuum  found excess emision at the Galactic Center GC 2-10 keV band flux (log scale) Fe K-line (6.7 keV) flux (linear scale) Galactic longitude at b=0 deg

4. The Closed-up View Near the Galactic Center ○ The 6.7 keV line region is extended Center Energy =6.7 keV He-like iron (West) Center Energy < 6.7 keV (East) 2-10 keV 6.7 keV line Beam size Center Energy

5. ASCA (X-ray CCD + Telescope) separated the K-shell lines into the 6.7 (He-like), 7.0 (H-like) and 6.4 keV (neutral) lines We found 6.4 keV clumps at the molecular clouds, Sgr B and Sgr A. ---> puzzle is solved. The spectrum has strong iron line and large absorption near the iron K-edge at 7.1 keV. Fluorescence by external X- rays No bright X-ray source is found The illuminating source was bright in the past, but faint at present

6. The Center of the Galaxy in the Recent Past: A view from GRANAT Sunyaev et al. 1993, ASCA View of Our Galactic Center: Remains of Past Activities in X-Rays? Koyama et al., 1996, PASJ, 48. Rasid Sunyaev and I met with each other with the same idea.

7. Suzaku found K α lines of highly ionized Ar, Ca, Cr, Mn, Fe and Ni (red) and those of neutral (blue ) :Z= 1.6 solar 4 solar The EWs ( absolute values and distribution pattern) are consistent with the X-ray fluorescent origin from clouds of 1.6 solar abundances. Electron origin requires more than 4 solar for all elements !

8. l-distribution of the 6.4 keV lines Sgr A Discoveries of New 6.4 keV Clouds Sgr B2 Sgr B1 M0.74-0.09 M359.43-0.07 M359.47-0.15 M359.43-0.12 M359.38-0.00 M359.23-0.04 M0.1-0.1 Arches G0.174-0.223 G0.162-0.127

9. 1994 年 2004 年 2005 年 2000 年 Rapid Time-Varaibility of Sgr B2 6.4 keV line :Koyama et al. 2008, Inui et al. 2009, Hard X-rays :Terrier et al. 2010 ASCA XMM-Newton Chandra Suzaku

10. Suzaku found simultaneous variablity of the 6.4 keV line & Hard X-rays in Sgr B2 2005 2009 The rapid/simultaneous variability strongly supports the X-ray fluorescence origin irradiated by an external big but short X-ray flare. What is the external flare ?

11. Parabola x 2 +y 2 =(300-y) 2 (Unit is light-year) Sgr A* Flare ~300 years ago Fermi bubble ? Quasar-like activity 1Myears ago （ Su, M. et al. 2010) Face-on View of the 6.4 keV cloud (e.g. Ryu et al. 2009) Near side GCDX is not absorbed by the cloud, while far side is heavily absorbed by the cloud. => Face on position of the cloud

12. The END