Suzaku Observation of the Unidentified Very High Energy Gamma-Ray Source HESS J1702-420
Suzaku Observation of the Unidentified Very High Energy Gamma-Ray Source HESS J1702-420
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DOI：
10.1093/pasj/63.sp3.s857
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发表时间：
2011-06
影响因子：
2.3
通讯作者：
T. Fujinaga;A. Bamba;T. Dotani;M. Ozaki;G. Puehlhofer;S. Wagner;O. Reimer;S. Funk;J. Hinton
中科院分区：
文献类型：
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作者：
T. Fujinaga;A. Bamba;T. Dotani;M. Ozaki;G. Puehlhofer;S. Wagner;O. Reimer;S. Funk;J. Hinton
朱雀号首次对未经确认的甚高能量（VHE）伽马射线源HESS J1702 - 420进行了深X射线观测。除了两个微弱的点状源外，在XIS视场（FOV）中没有检测到明亮的源。然而，这两个源被认为与HESS J1702 - 420无关，因为它们在2 - 10 keV波段（~10 ^-14 erg s ^-1 cm ^-2）的通量比VHE在1 - 10 TeV波段（F_{TeV}= 3.1 x 10 ^-11 erg s ^-1 cm ^-2）的伽马射线通量小~3个数量级。我们比较了漫发射的能谱，从整个XIS FOV提取与附近的观测。如果我们考虑背景扣除的系统误差，那么在2 - 10 keV波段，如果假设γ = 2.1的幂律谱和与VHE波段相同的源尺寸，则在F_X <2.7 x 10 ^-12 erg s ^-1 cm ^-2的上限下，没有检测到明显的漫发射。X射线通量的上限是VHE γ射线通量的十二倍。大的通量比（F_{TeV}/F_X）表明HESS J1702 - 420是"暗"粒子加速器的又一实例。如果我们使用一个简单的单区轻子模型，其中VHE伽马射线是通过宇宙微波背景和星际远红外辐射的逆康普顿散射产生的，X射线是通过同步加速器机制产生的，磁场的上限（1.7 μ G）从通量比得到。由于磁场比银河平面的典型值（3 - 10 μ G）弱，简单的单区模型可能不适用于HESS J1702 - 420，并且VHE伽马射线的很大一部分可能来自质子。
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 (~ 10^-14 erg s^-1 cm^-2) are ~ 3 orders of magnitude smaller than the VHE gamma-ray flux in the 1-10 TeV band (F_{TeV} = 3.1 x 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_X <2.7 x 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_{TeV}/F_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.