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X-ray and near-infrared ( $J$– $H$– $K_{\rm s}$) observations of the galactic black-hole binary GX 339 $-$4 in the low/hard state were performed with Suzaku and IRSF in 2009 March. The spectrum in the 0.5–300 keV band is dominated by thermal Comptonization of multicolor disk photons, with a small contribution from a direct disk component, indicating that the inner disk is almost fully covered by hot corona with an electron temperature of $\approx$175 keV. The Comptonizing corona has at least two optical depths, $\tau$$\approx$1, 0.4. Analysis of the iron-K line profile yields an inner-disk radius of (13.3 $^{+6.4}_{-6.0}$) $\ R_{\rm g}$( $\ R_{\rm g}$represents the gravitational radius $GM/c^2$), with the best-fit inclination angle of $\approx$50 $^\circ$. This radius is consistent with that estimated from the continuum fit by assuming the conservation of photon numbers in Comptonization. Our results suggest that the standard disk of GX 339 $-$4 is likely truncated before reaching the innermost stable circular orbit (for a non-rotating black hole) in the low/hard states at $\sim\ $1% of the Eddington luminosity. The one-day averaged near-infrared light curves are found to be correlated with hard X-ray flux with $F_{\rm Ks}$$\propto$$F_{\rm X}^{0.45}$. The flatter near-infrared $\nu F_{\nu}$spectrum than the radio one suggests that the optically thin synchrotron radiation from the compact jets dominates the near-infrared flux. Based on a simple analysis, we estimate the magnetic field and size of the jet base to be 5 $\times$10 $^{4}\ $G and 6 $\times$10 $^{8}\ $cm, respectively. The synchrotron self Compton component is estimated to be approximately 0.4% of the total X-ray flux.

The stellar distribution derived from an H- and KS-band survey of the central region of our Galaxy is compared with the Fe xxvKα (6.7 keV) line intensity observed with the Suzaku satellite. The survey is for the galactic coordinates |l| ≲ 3$_{.}^{\circ}$0 and |b| ≲ 1$_{.}^{\circ}$0 (equivalent to 0.8 kpc × 0.3 kpc for R⊙= 8 kpc), and the number-density distribution N(KS,0; l, b) of stars is derived by using the extinction-corrected magnitude KS,0= 10.5. This is deep enough to probe the old red-giant population and in turn to estimate the (l, b) distribution of faint X-ray point sources such as coronally active binaries and cataclysmic variables. In the Galactic plane (b= 0°), N(10.5; l, b) increases in the direction of the Galactic center as |l|−0.30±0.03in the range of − 0$_{.}^{\circ}$1 ≥ l≥ − 0$_{.}^{\circ}$7, but this increase is significantly slower than the increase (|l|−0.44±0.02) of the Fe xxvKα line intensity. If normalized with the ratios in the outer region 1$_{.}^{\circ}$5 ≤ |l| ≤ 2$_{.}^{\circ}$8, where faint X-ray point sources are argued to dominate the diffuse Galactic X-ray ridge emission, the excess of the Fe xxvKα line intensity over the stellar number density is at least a factor of two at |l| = 0$_{.}^{\circ}$1. This indicates that a significant part of the Galactic-center diffuse emission arises from a truly diffuse optically thin thermal plasma, and not from an unresolved collection of faint X-ray point sources related to the old stellar population.