Detection of the high energy cut-off from the Seyfert 1.5 galaxy NGC 5273
Detection of the high energy cut-off from the Seyfert 1.5 galaxy NGC 5273
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DOI：
10.1093/mnras/stx1455
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发表时间：
2017-06
影响因子：
4.8
通讯作者：
M. Pahari;I. McHardy;L. Mallick;G. Dewangan;R. Misra
中科院分区：
文献类型：
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作者：
M. Pahari;I. McHardy;L. Mallick;G. Dewangan;R. Misra
我们对宽线Seyfert 1.5星系NGC5273的同时观测数据进行了NuSTAR和SWIFT/XRT联合能谱拟合。当结合指数截止幂定律和反射模型时，在143^(+96)_(−40)keV处探测到一个2σ意义的高能截止。当单独用康普顿化模型拟合时，这种截止的存在与观测到的康普顿化电子温度是一致的。我们在20-100keV的能量范围内使用积分/∼观测观测到了该源在12年的时间尺度上的中等硬X射线变率。当绘制硬带计数率(6-20keV)与软带计数率(3-6keV)的曲线图时，观察到硬偏移。我们的结果表明，截止能量可能不是简单地与日冕X射线光度相关的。描述日冕性质的参数的相似性表明，NGC5273的日冕结构可能类似于宽线射电星系3C 390.3和另一个星系MCG-5-23-16，在这些星系中，日冕等离子体由电子主导，而不是电子-正电子对。因此，即使在低吸积率下，日冕冷却对于保持低截止能量的加热机制也是同样有效的。
We perform the NuSTAR and Swift/XRT joint energy spectral fitting of simultaneous observations from the broad-line Seyfert 1.5 galaxy NGC 5273. When fitted with the combination of an exponential cut-off power law and a reflection model, a high-energy cut-off is detected at 143 ^(+96)_(−40) keV with 2σ significance. Existence of such cut-off is also consistent with the observed Comptonizing electron temperature when fitted with a Comptonization model independently. We observe a moderate hard X-ray variability of the source over the time-scale of ∼12 yr using INTEGRAL/ISGRI observations in the energy range of 20–100 keV. When the hard-band count rate (6–20 keV) is plotted against the soft-band count rate (3–6 keV), a hard offset is observed. Our results indicate that the cut-off energy may not correlate with the coronal X-ray luminosity in a simple manner. Similarities in parameters that describe coronal properties indicate that the coronal structure of NGC 5273 may be similar to that of the broad-line radio galaxy 3C 390.3 and another galaxy MCG-5-23-16, where the coronal plasma is dominated by electrons, rather than electron–positron pairs. Therefore, the coronal cooling is equally efficient to the heating mechanism keeping the cut-off energy at low even at the low accretion rate.