M87的TeV辐射光变

2005年第一次在M87中观测到TeV辐射爆发,分析表明TeV爆发的光变时标非常短且相对孤立.M87的喷流的视向倾角较大(～30?),是银河系外观测到的第一个非blazar类TeV源,这暗示着新的产生TeV辐射过程.考虑到TeV源有可能是产生于黑洞吸积盘上的等离子体云团,刚诞生的时候可能围绕中心黑洞作开普勒运动,本文在完全广义相对论框架下计算了这种情况下TeV辐射的光变.模型中不仅考虑了TeV源作开普勒运动的效应,还计算了轨道上不同点发出的TeV光子在到达无穷远处观测者的过程中被来自吸积盘上的软光子吸收的光深差异.计算表明TeV源的光变主要由不同轨道上的TeV光子的光深变化主导,TeV源作开普勒运动的效应基本可以忽略.在TeV源距离黑洞比较近的时候,随着黑洞自旋的增大光深显著减小,在黑洞自旋为零时,光深变化曲线明显不对称,TeV源越靠近黑洞这些效应越显著.

Variation of TeV emission from M87

In 2005, TeV flare from M87 was observed for the first time, which shows that the TeV flares are in a very short time scale, and detached. The viewing angle of the jet of M87 is very large, it is the first non-blazar like extragalactic TeV source, which might indicate a new production process for TeV emission. Possibly, the TeV source might be the hot plasma clouds from the accretion flow around black hole, these clouds might initially be in Keplerian orbits. In this work, the variation of the TeV emission is investigated in the framework of general relativity. In our model, both the effects of the Keplerian motion of the source and the different absorption optical depth of the TeV photons from the different locations of the source. The absorption of TeV photons is due to its collision with soft photons from the accretion disk. Our results show that variation of TeV emission is mainly dominated by their optical depth, the effect of the dynamical motion of the source could be neglected. When the TeV source is close to the central black hole, the optical depth significantly decreases with the increase of the black hole spin. If the black hole is non-rotating, the flux variation is obviously asymmetric. As the TeV source closes to black hole, their effects are enhanced.