CHARGE-STARVED, RELATIVISTIC JETS AND BLAZAR VARIABILITY
CHARGE-STARVED, RELATIVISTIC JETS AND BLAZAR VARIABILITY
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DOI：
10.1088/0004-637x/729/2/104
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发表时间：
2010-12
期刊：
影响因子：
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通讯作者：
J. Kirk;Iwona Mochol
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文献类型：
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作者：
J. Kirk;Iwona Mochol
人们认为，由超大质量黑洞发射的相对论喷流中，会产生来自blazar的高能量辐射。发射位置必须远离空穴和喷流相对论，以避免吸收光子。在极端情况下，辐射的快速变化表明，喷流发射时，长度尺度小于中心黑洞引力半径的结构被印记在喷流上，并对加速到高洛伦兹因子后释放的辐射进行调制。基于大振幅波在电荷匮乏的极地喷流中的传播特性，我们提出了一种可以解释喷流加速和辐射快速变化的机制。使用双流体(e±)描述，我们发现，当与波流相关的惯性变得重要时，外流表现出延迟的加速阶段。流体随波以大约音速传播，对应于体积洛伦兹因子向半径扩展，之后波洛伦兹因子以γw∝r加速，流体以γ∝r2加速。(Δt100是以100为单位的可变性时间S，是在一个引力半径下的多重性对，L46是喷流的“4π光度”，单位为1046erg S-1，M9是黑洞质量，单位为109M☉)发射时印在喷流上的时间结构调制了由所提供的加速喷流产生的光子，这表明非常快速的变率仅限于黑洞磁层电磁级联不多的源。
High energy emission from blazars is thought to arise in a relativistic jet launched by a supermassive black hole. The emission site must be far from the hole and the jet relativistic, in order to avoid absorption of the photons. In extreme cases, rapid variability of the emission suggests that structures of length scale smaller than the gravitational radius of the central black hole are imprinted on the jet as it is launched and modulate the radiation released after it has been accelerated to high Lorentz factor. We propose a mechanism which can account for the acceleration of the jet, and for the rapid variability of the radiation, based on the propagation characteristics of large-amplitude waves in charge-starved, polar jets. Using a two-fluid (e±) description, we find that the outflows exhibit a delayed acceleration phase that starts when the inertia associated with the wave currents becomes important. The fluids propagate with the wave at approximately the sonic speed, corresponding to a bulk Lorentz factor out to radius , after which the wave Lorentz factor accelerates as γw ∝ r, and that of the fluids as γ ∝ r2. (Δt100 is the variability time in units of 100 s, is the pair multiplicity at one gravitational radius, L46 is the “4π-luminosity” of the jet in units of 1046 erg s-1, and M9 is the black hole mass in units of 109 M☉) The time structure imprinted on the jet at launch modulates photons produced by the accelerating jet provided , suggesting that very rapid variability is confined to sources in which the electromagnetic cascade in the black hole magnetosphere is not prolific.