  The soft X-ray background shows a general enhancement toward the inner region
of the Galaxy. But whether this enhancement is a local feature (e.g., a
superbubble within a distance of <= 200 pc) and/or a phenomenon related to
energetic outflows from the Galactic center/bulge remains unclear. Here we
report a comparative X-ray emission and absorption study of diffuse hot gas
along the sight lines toward 3C 273 and Mrk 421, on and off the enhancement,
but at similar Galactic latitudes. The diffuse 3/4-keV emission intensity, as
estimated from the ROSAT All Sky Survey, is about three times higher toward 3C
273 than toward Mrk 421. Based on archival \chandra grating observations of
these two AGNs, we detect X-ray absorption lines (e.g., OVII Kalpha, Kbeta, and
OVIII Kalpha transitions at z~0) and find that the mean hot gas thermal and
kinematic properties along the two sight lines are significantly different. By
subtracting the foreground and background contribution, as determined along the
Mrk 421 sight line, we isolate the net X-ray absorption and emission produced
by the hot gas associated with the enhancement in the direction of 3C 273. From
a joint analysis of these differential data sets, we obtain the temperature,
dispersion velocity, and hydrogen column density as 2.0(1.6, 2.3)E6 K,
216(104,480) km/s, and 2.2(1.4, 4.1)E19 cm^{-2}, respectively (90% confidence
intervals), assuming that the gas is approximately isothermal, solar in metal
abundances, and equilibrium in collisional ionization. We also constrain the
effective line-of-sight extent of the gas to be 3.4(1.0, 10.1) kpc, strongly
suggesting that the enhancement most likely represents a Galactic central
phenomenon.
