Suzaku Observations of HESS J1616—508: Evidence for a Dark Particle Accelerator

Abstract

Abstract We observed the bright unidentified TeV $\gamma$-ray source HESS J1616$-$508 with the X-ray Imaging Spectrometers onboard the Suzaku satellite. No X-ray counterpart was found to a limiting flux of $3.1 \times 10^{-13} \,\mathrm{erg} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2}$ in the 2–10 keV band, which is some 60-times below the $\gamma$-ray flux in the 1–10TeV band. This object is bright in TeV $\gamma$-rays, but very dim in the X-ray band, and thus is one of the best examples in the Galaxy of a “dark particle accelerator.” We also detected soft thermal emission with $kT \sim 0.3 \hbox{--} 0.6 \,\mathrm{keV}$ near the location of HESS J1616$-$508. This may be due to a dust-grain scattering halo from the nearby bright supernova remnant RCW 103.