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Session 62 - X-ray Astronomy: New Discoveries.
Oral session, Tuesday, January 16
1st Floor, La Villita Assembly Building
X-ray imaging spectroscopic observations near the Galactic Center region in the 0.5-10 keV band were carried out with the ASCA satellite. Two bright spots close to the Galactic Center (Sgr A*) are found; one is a hot plasma with strong line emissions of highly ionized iron and the other is a newly discovered eclipsing X-ray burster with a largely absorbed spectrum. It is probable that the previous reports on the X-ray flux from the Galactic Center were contaminated by this X-ray burster. Further extended hot plasma with K- shell transition lines of highly ionized silicon sulfur argon and iron is also found. Spatially resolved spectra from the Center region are found to be identical from place to place, except for the amount of low energy absorption and the absolute flux. Another remarkable discovery is 6.4 keV line emissions of low ionization iron atoms near the Sgr B2 cloud and the Radio Arc region. We interpret that the 6.4 keV line originates from the florescent from the gas cloud irradiated by strong X-ray beams, which is now quiet but had been active until the recent past. The origin of the hot plasma may also be related to the past possible activity at the Galactic Center.
Program listing for Tuesday