Blazars emit a highly variable non-thermal spectrum. It is usually assumed that the same non-thermal electrons are responsible for the IR-optical-UV emission (via synchrotron) and the gamma-ray emission (via inverse Compton). Hence, the light curves in the two bands should be correlated. Orphan gamma-ray flares (i.e. lacking a luminous low-frequency counterpart) challenge our theoretical understanding of blazars. By means of large-scale two-dimensional radiative particle-in-cell simulations, we show that orphan gamma-ray flares may be a self-consistent by-product of particle energization in turbulent magnetically dominated pair plasmas. The energized particles produce the gamma-ray flare by inverse Compton scattering an external radiation field, while the synchrotron luminosity is heavily suppressed since the particles are accelerated nearly along the direction of the local magnetic field. The ratio of inverse Compton to synchrotron luminosity is sensitive to the initial strength of turbulent fluctuations (a larger degree of turbulent fluctuations weakens the anisotropy of the energized particles, thus increasing the synchrotron luminosity). Our results show that the anisotropy of the non-thermal particle population is key to modelling the blazar emission.

中文翻译：

---

耀变体中孤儿伽马射线耀斑的全动力学模型

耀变体发出高度可变的非热光谱。通常假设相同的非热电子负责红外-光学-紫外发射（通过同步加速器）和伽马射线发射（通过逆康普顿）。因此，两个波段中的光变曲线应该是相关的。孤儿伽马射线耀斑（即缺乏发光的低频对应物）挑战了我们对耀变体的理论理解。通过大规模二维辐射粒子细胞模拟，我们表明孤儿伽马射线耀斑可能是湍流磁主导对等离子体中粒子激励的自洽副产品。通电粒子通过反向康普顿散射外部辐射场产生伽马射线耀斑，而同步加速器的光度被严重抑制，因为粒子几乎沿着局部磁场的方向加速。逆康普顿与同步加速器光度的比值对湍流涨落的初始强度敏感（较大程度的湍流涨落会削弱激发粒子的各向异性，从而增加同步加速器光度）。我们的结果表明，非热粒子群的各向异性是模拟耀变体发射的关键。