An X-ray Spectroscopic Study of the Hot Interstellar Medium Toward the
  Galactic Bulge
  We present a detailed spectroscopic study of the hot gas toward the Galactic
bulge along the 4U 1820-303 sight line by a combination analysis of emission
and absorption spectra. In addition to the absorption lines of OVII Kalpha,
OVII Kbeta, OVIII Kalpha and NeIX Kalpha by Chandra LTGS as shown by previous
works, Suzaku detected clearly the emission lines of OVII, OVIII, NeIX and NeX
from the vicinity. We used simplified plasma models with constant temperature
and density. Evaluation of the background and foreground emission was performed
carefully, including stellar X-ray contribution based on the recent X-ray
observational results and stellar distribution simulator. If we assume that one
plasma component exists in front of 4U1820-303 and the other one at the back,
the obtained temperatures are T= 1.7 +/- 0.2 MK for the front-side plasma and
T=3.9(+0.4-0.3) MK for the backside. This scheme is consistent with a hot and
thick ISM disk as suggested by the extragalactic source observations and an
X-ray bulge around the Galactic center.
