A PHOTO-HADRONIC MODEL OF THE LARGE-SCALE JET OF PKS 0637-752
A PHOTO-HADRONIC MODEL OF THE LARGE-SCALE JET OF PKS 0637-752
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DOI：
10.3847/1538-4357/835/1/20
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发表时间：
2016-11
期刊：
影响因子：
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通讯作者：
M. Kusunose;F. Takahara
中科院分区：
文献类型：
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作者：
M. Kusunose;F. Takahara
大范围射电响亮类星体喷流的强X射线辐射仍然是一个悬而未决的问题。最近，由于费米LAT对3C273和PKS0637-752的观测给出的上限远低于模型预测，基于相对论光束喷流对宇宙微波背景光子的逆康普顿散射的模型已被排除。来自具有数百TeV能量的独立电子群体的同步辐射仍然是可能的，尽管它的来源还不是很清楚。我们研究了这种高能电子/正电子的光强子起源，假设质子被加速到1019 eV，并通过Bethe-Heitler过程和光电子产生产生电子/正电子。这些二次电子/正电子以足够高的能量注入，并通过同步辐射产生X射线和γ-射线，而不会与费米LAT上限冲突。我们发现，如果质子能量至少是高度超爱丁顿的，得到的谱很好地再现了PKS0637-752的X射线观测结果。值得注意的是，X射线辐射主要是通过Bethe-Heitler过程来自轻子，而来自光皮子起源的轻子通过多TeV光子的同步辐射而不是级联而直接损失能量。为了避免光通量的过剩，光发射主要是由于次级轻子的同步发射，而不是初级电子，或者如果是初级电子，则需要适度的束流。质子同步加速器的光度要小几个数量级。
Strong X-ray emission from large scale jets of radio loud quasars still remains an open problem. Models based on inverse Compton scattering off cosmic microwave background photons by relativistically beamed jets have recently been ruled out, since Fermi LAT observations for 3C 273 and PKS 0637–752 give the upper limit far below the model prediction. Synchrotron emission from a separate electron population with multi-hundred TeV energies remains a possibility although its origin is not well known. We examine a photo-hadronic origin of such high energy electrons/positrons, assuming that protons are accelerated up to 1019 eV and produce electrons/positrons through a Bethe–Heitler process and photo-pion production. These secondary electrons/positrons are injected at sufficiently high energies and produce X-rays and γ-rays by synchrotron radiation without conflicting with the Fermi LAT upper limits. We find that the resultant spectrum well reproduces the X-ray observations from PKS 0637-752, if the proton power is at least , which is highly super-Eddington. It is noted that the X-ray emission originates primarily from leptons through a Bethe–Heitler process, while leptons from photo-pion origin lose energy directly through synchrotron emission of multi-TeV photons rather than cascading. To avoid the overproduction of the optical flux, optical emission is primarily due to synchrotron emission of secondary leptons rather than primary electrons, or a mild degree of beaming of the jet is needed if it is owing to the primary electrons. Proton synchrotron luminosity is a few orders of magnitude smaller.