标题： MKN501喷流中的边界剪切加速度 显示英文标题

标题： Boundary Shear Acceleration in the Jet of MKN501

摘要： 高分辨率射电图像显示BL Lac天体MKN501喷流具有边缘增亮特征。这种特征被解释为由于喷流横向速度结构导致的喷流核心和喷流边界的不同多普勒增强的结果，这需要大的观测角度。然而，这种推论与高能$\gamma$-ray研究得出的约束相矛盾，除非喷流在$\gamma$-ray区域（靠近中心引擎）之后立即弯曲一个大角度。在本信中，我们通过考虑在边界剪切层加速的电子扩散到喷流介质中，提出了对MKN501边缘增亮特征的另一种解释，这种考虑不需要大的观测角度。此外，在喷流边界和喷流核心处观测到的光谱指数差异也可以在剪切加速的框架内得到理解。 显示英文摘要

摘要： The high resolution image of the jet of the BL Lac object MKN501 in radio, show a limb-brightened feature. An explanation of this feature as an outcome of differential Doppler boosting of jet spine and jet boundary due to transverse velocity structure of the jet requires large viewing angle. However this inference contradicts with the constraints derived from the high energy $\gamma$-ray studies unless the jets bends over a large angle immediately after the $\gamma$-ray zone (close to the central engine). In this letter we propose an alternate explanation to the limb-brightened feature of MKN501 by considering the diffusion of electrons accelerated at the boundary shear layer into the jet medium and this consideration does not require large viewing angle. Also the observed difference in the spectral index at the jet boundary and jet spine can be understood within the frame work of shear acceleration.