We report the discovery of an X-ray counterpart of the unidentified very high energy gamma-ray source HESS J1427-608. In the sky field coincident with HESS J1427-608, an extended source was found in the 2-8 keV band, and was designated as Suzaku J1427-6051. Its X-ray radial profile has an extension of σ = 0. ′ 9 ± 0. ′ 1 if approximated by a Gaussian. The spectrum was well fitted by an absorbed power-law with N H = (1.1 ± 0.3) × 10 23 cm −2 , Γ = 3.1 +0.6 −0.5 , and the unabsorbed flux F X = (9 +4 −2 ) × 10 −13 erg s −1 cm −2 in the 2-10 keV band. Using XMM-Newton archive data, we found seven point sources in the Suzaku source region. However, because their total flux and absorbing column densities are more than an order of magnitude lower than those of Suzaku J1427-6051, we consider that they are unrelated to the Suzaku source. Thus, Suzaku J1427-6051 is considered to be a truly diffuse source and an X-ray counterpart of HESS J1427-608. The possible nature of HESS J1427-608 is discussed based on the observational properties.

A deep X-ray observation of the unidentified very high energy (VHE) gamma-ray source HESS J1702 $-$ 420, for the first time, was carried out by Suzaku. No bright sources were detected in the XIS field of view (FOV), except for two faint point-like sources. The two sources, however, are considered not to be related to HESS J1702 $-$ 420, because their fluxes in the 2–10 keV band ( $\sim\ $ 10 $^{-14}\ $ erg s $^{-1}\ $ cm $^{-2}$ ) are $\sim\ $ 3 orders of magnitude smaller than the VHE gamma-ray flux in the 1–10 TeV band ( $F_{\rm TeV}$$=$ 3.1 $\times$ 10 $^{-11}\ $ erg s $^{-1}\ $ cm $^{-2}$ ). We compared the energy spectrum of diffuse emission, extracted from the entire XIS FOV with those from nearby observations. If we consider the systematic error of background subtraction, no significant diffuse emission was detected with an upper limit of $F_{\rm X}$$<$ 2.7 $\times$ 10 $^{-12}\ $ erg s $^{-1}\ $ cm $^{-2}$ in the 2–10 keV band for an assumed power-law spectrum of $\Gamma$$=$ 2.1 and a source size same as that in the VHE band. The upper limit of the X-ray flux is twelve-times as small as the VHE gamma-ray flux. The large flux ratio ( $F_{\rm TeV}/F_{\rm X}$ ) indicates that HESS J1702 $-$ 420 is another example of a “dark” particle accelerator. If we use a simple one-zone leptonic model, in which VHE gamma-rays are produced through inverse Compton scattering of the cosmic microwave background and interstellar far-infrared emission, and the X-rays via the synchrotron mechanism, an upper limit of the magnetic field (1.7 $\ \mu$ G) is obtained from the flux ratio. Because the magnetic field is weaker than the typical value in the galactic plane (3–10 $\ \mu$ G), the simple one-zone model may not work for HESS J1702 $-$ 420 and a significant fraction of the VHE gamma-rays may originate from protons.

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