Nature of the Unidentified TeV Source HESS J1614−518, Revealed by Suzaku and XMM-Newton Observations

Abstract

Abstract We report on new Suzaku and XMM-Newton results concerning HESS J1614 $-$ 518, which is one of the brightest extended TeV $\gamma$ -ray sources and has two regions with intense $\gamma$ -ray emission. We newly observed the south and center regions of HESS J1614 $-$ 518 with Suzaku, since the north region, including the position of the 1st brightest peak of the TeV $\gamma$ -ray emission, has already been observed. No X-ray counterpart was found at the position of the 2nd brightest peak of the TeV $\gamma$ -ray emission; we estimated the upper limit of the X-ray flux to be 1.6 $\times$ 10 $^{-13}$ erg cm $^{-2}$ s $^{-1}$ in the 2–10 keV band. The soft X-ray source Suzaku J1614 $-$ 5152, which was found at the edge of the field of view in a previous observation, was also detected at the middle of HESS J1614 $-$ 518. Analyzing the XMM-Newton archival data, we revealed that Suzaku J1614 $-$ 5152 consists of multiple point sources. The X-ray spectrum of the brightest point source, XMMU J161406.0 $-$ 515225, can be described by a power-law model with a photon index of $\Gamma$$=$ 5.2 $^{+0.6}_{-0.5}$ , or a blackbody model with temperature $kT$$=$ 0.38 $^{+0.04}_{-0.04}$ keV. In the blackbody model, the hydrogen-equivalent column density is almost the same as that of the hard extended X-ray emission, Suzaku J1614 $-$ 5141, which was found at the 1st peak position. If true, XMMU J161406.0 $-$ 515225 may be physically related to Suzaku J1614 $-$ 5141 and HESS J1614 $-$ 518.