1) Origin of 6.7/6.9 keV (He-like/H-like Fe Ka) Lines : Collisional Excitation or Charge Exchange 2) Discoveries of New SNR Candidates 3) Origin of 6.4 keV (Neutral Fe Ka) Line : X-Ray Reflection or Electron Bremsstrah ｌ ung : Time Variability of the 6.4 keV clumps How reliable our “Energy scale calibration” is. (For detail, please read PASJ special issue) Spectroscopic Study of the Galactic Center X-Rays with Suzaku Katsuji Koyama, Kyoto University

H-like Observed (eV) Lab D(eV) S Lya 2622 (+4-3) Fe Lya 6970 (+3-2) Mn Ka 5900 (+2-1) Origin of the 6.7 keV (He-like Fe Ka) Line Charge Exchange or Collisional Excitation ? Collisional Excitation  eV Charge Exchange  6666eV r r f f i i He-like Ka complex He-like Fe Ka = 6680 (+-1) eV： Close to eV in Collisional Excitation Energy Scale Check Using the H-like Lya   and Neutral Ka 

Lyman Series n>8  n=1 Collisional Excitation （ High Temperature Plasma ） is more ｌ ikely Origin for 6.9 keV 6.9 keV (H-like Lya  is very narrow < 20 eV = Fe velocity < 1000 km/s

Ionization Temperature (kTi) Fe Ka H-like/He-like: kTi=6.5 keV +/- 0.1 keV Fe Kb H-like/He-like: kTi=5.1 keV keV Ni Ka H-like/He-like : kTi=9.3 keV keV Electron Temperature (kTe) He-like Fe Kb/Ka : kTe=6.2 keV keV H-like Fe Kb/Ka : kTe > 6.5 keV (lower limi ｔ ) All the results are consitent with the plasma of kTi = kTe (CIE) = 6.5 keV. Centroid of He-like Ka moves with Ionization temperature due to the satellite lines. The Center Energy of Ka (He-like) : kTi= keV Parameters of the GC plasma

2. Discovery of New SNR Candidates 6.7 keV map 2.45 keV map Sgr A East

3. Discovery of 6.4 keV clumps Origin of the 6.4 keV clumps Is this Inner shell Ionization by Electrons or X-rays ? 6.4 keV Map

Inner Shell Ionization Electrons ｖｓ Ｘ -rays Equivalent witdh (keV) of the 6.4 keV line Energy (keV) of the Max Cross Section Absorption N H (cm -2 )~10 21 ~10 24 １０ ２１ １０ ２４ Electron X-ray

Most of the 6.4 keV clumps show strong Ka line with the equivalent width of 1.1 – 2.1 keV,and deep K-edge absorption with 2 – 10 x cm -2 >> 1 x cm -2 ( the interstellar absorption to the GC) Thus ionization by X-rays is more likely. Further more We found a large time variability.

6.4 keV line History of Sgr B2 from 1994 to 2005 ~10pc Sgr B2 G0.570

6.7keV: Full region 6.4keV: Full region 6.4keV: G keV: Sgr B2 cloud 6.4 keV 6.7keV

Physical size of the clump complex is nearly 10 pc. Therefore, such a large flux change within 10 years is impossible by any charged particle. Only possible scenario of this time variability is due to an irradiation of variable X-rays (X-ray Reflection Nebula). More than a few hundred years ago, Sgr A* had been very active in X-rays; it was 10 6 times brighter than present at ~300 years ago, and decayed to less than a half after ~10 years. The X-rays hit the Sgr B clouds after ~300-years travel. The clouds re- emitted the 6.4 keV photons. Like a time delayed- echo, the X-ray echo is now just arriving at the Earth, when Sgr A* is falling into a quiescent state.

(1) Origin of the 6.7/6.9 keV Lines High Temperature Plasma in CIE (2) We have discovered New SNR Candidates (3) Origin of the 6.4 keV Line X-Ray Reflection The 6.4 keV clumps near Sgr B2 are time variable as a reflection of a past outburst of Sg A* Conclusion of the Galactic Center Diffuse X-rays