标题： 高能质量星系中的伽马射线变化：喷流引起的风团块化 显示英文标题

标题： Gamma-ray variability from wind clumping in HMXBs with jets

摘要： 在被称为“微类星体”的高能质量X射线双星子类中，由致密天体喷出的相对论性强子可以与来自恒星辐射驱动风的冷质子相互作用，产生派生粒子随后迅速衰变为伽马射线。 由于产生的伽马射线发射率依赖于目标密度，利用GLAST和新一代切伦科夫成像阵列探测微类星体的快速变化可能被用来研究恒星风的团块结构。 我们在这里表明，伽马射线的变化可以用一种“多孔长度”形式来建模，这种形式通常用于表征团块效应。 特别是，对于由h=l/f定义的多孔长度，即团块特征尺寸l与其体积填充因子f的比值，我们发现，在轨道分离为a的双星系统中伽马射线发射的相对变化，在“细喷流”极限下随sqrt(h/pi a)缩放，并且对于具有有限张角phi的喷流，通过因子1/sqrt(1 + phi a/(2 l))减少。 对于细喷流和相当小的多孔长度h ~ 0.03 a，这意味着伽马射线发射大约有10%的变化。 此外，单个大团块的照射可能导致孤立的耀斑，正如最近在一些大质量伽马射线双星中观察到的那样。 显示英文摘要

摘要： In the subclass of high-mass X-ray binaries known as "microquasars", relativistic hadrons in the jets launched by the compact object can interact with cold protons from the star's radiatively driven wind, producing pions that then quickly decay into gamma rays. Since the resulting gamma-ray emissivity depends on the target density, the detection of rapid variability in microquasars with GLAST and the new generation of Cherenkov imaging arrays could be used to probe the clumped structure of the stellar wind. We show here that the fluctuation in gamma rays can be modeled using a "porosity length" formalism, usually applied to characterize clumping effects. In particular, for a porosity length defined by h=l/f, i.e. as the ratio of the characteristic size l of clumps to their volume filling factor f, we find that the relative fluctuation in gamma-ray emission in a binary with orbital separation a scales as sqrt(h/pi a) in the "thin-jet" limit, and is reduced by a factor 1/sqrt(1 + phi a/(2 l)) for a jet with a finite opening angle phi. For a thin jet and quite moderate porosity length h ~ 0.03 a, this implies a ca. 10 % variation in the gamma-ray emission. Moreover, the illumination of individual large clumps might result in isolated flares, as has been recently observed in some massive gamma-ray binaries.