康普顿火箭和相对论喷流的最小功率
Compton rockets and the minimum power of relativistic jets
摘要：
相对论性喷流的能量取决于喷流本身携带的轻子和质子的数量。我们有理由相信，强大的伽马射线平谱射电源在辐射冷却严重的地方发出大部分辐射。这有助于找到解释我们所看到的辐射所需的最小发射轻子数。质子的数量更不确定。如果每个电子有一个质子，它们就主导了喷流的能量，但如果发射是由于电子-正电子对，它们就不重要了。在这种情况下，总的喷气动力可以小得多。然而，如果伽马射线通量是由于逆康普顿散射与射流外部产生的种子光子，辐射也是各向异性的共动框架，使射流反冲。这种康普顿火箭效应对于轻的电子-正电子喷流很强，对于重的质子主导的喷流可以忽略不计。快速超光速运动不需要显著的减速，这就要求每个轻子有最小的质子数，因此也就有最小的喷流功率。我们将这些想法应用到blazar 3C 454.3中，找到了它的总喷流功率的一个鲁棒的下限：对于任何体洛伦兹因子γ，如果视角θ_v ~ 1/γ，喷流功率大于吸积光度L_d。相反，对于theta_v =0，最小喷射功率可以小于Gamma<25的L_d。每个质子不允许超过~10对。
英文摘要：
The power of a relativistic jet depends on the number of leptons and protons carried by the jet itself. We have reasons to believe that powerful gamma-ray flat spectrum radio sources emit most of their radiation where radiative cooling is severe. This helps to find the minimum number of emitting leptons needed to explain the radiation we see. The number of protons is more uncertain. If there is one proton per electron, they dominate the jet power, but they could be unimportant if the emission is due to electron-positron pairs. In this case the total jet power could be much smaller. However, if the gamma-ray flux is due to inverse Compton scattering with seed photons produced outside the jet, the radiation is anisotropic also in the comoving frame, making the jet to recoil. This Compton rocket effect is strong for light, electron-positron jets, and negligible for heavy, proton dominated jets. No significant deceleration, required by fast superluminal motion, requires a minimum number of protons per lepton, and thus a minimum jet power. We apply these ideas to the blazar 3C 454.3, to find a robust lower limit to its total jet power: if the viewing angle theta_v ~ 1/Gamma the jet power is larger than the accretion luminosity L_d for any bulk Lorentz factor Gamma. For theta_v =0, instead, the minimum jet power can be smaller than L_d for Gamma<25. No more than ~10 pairs per proton are allowed.
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