微类星体遗迹的宽带辐射
Broadband emission of microquasar remnants
AI总结：
本研究建模微类星体遗迹的宽带辐射，发现其可作为隐藏的银河系延展非热源，强大遗迹可通过射电和软X射线探测，亚爱丁顿遗迹更难识别。
AI中文摘要：
微类星体遗迹（MQRs）是已消亡的微类星体喷流膨胀形成的长寿命茧状物，近期被认为是隐藏的银河系PeVatron（拍伏加速器），无需活跃中心引擎即可产生超高能伽马射线。强子相互作用可解释邻近云团的明亮伽马射线辐射，但MQRs的直接探测仍具挑战，因其本征辐射预计是延展且表面亮度低的。本研究聚焦于茧内的轻子成分及周围激波壳中的粒子相互作用，探究MQRs的宽带辐射。我们对相对论性粒子的注入和时变输运进行建模，其中包括由内部湍流驱动的随机再加速（视为二阶费米过程）。我们考虑亚爱丁顿和超爱丁顿微类星体系统，计算从射电到伽马射线能段的非热辐射，以及激波壳产生的热软X射线辐射。超爱丁顿情形下，本征辐射的峰值达到νL_ν ~ 10^35-10^36 erg·s^-1，而亚爱丁顿遗迹通常暗数个数量级。在1.3 GHz频率下，年轻强大遗迹的建模茧表面亮度约为Σ_ν ~ 10^-19 W·m^-2·Hz^-1·sr^-1，且随遗迹演化迅速降低。我们发现，MQRs的直接可探测性主要由表面亮度而非积分光度控制，强大遗迹可作为延展同步辐射射电茧和壳主导的软X射线结构被探测，而亚爱丁顿遗迹预计更难直接识别。我们的结果表明，MQRs可能构成隐藏的银河系延展非热源族群。
英文摘要：
Microquasar remnants (MQRs), the long-lived cocoons inflated by extinct microquasar jets, have recently been proposed as hidden Galactic PeVatrons capable of producing ultra-high-energy gamma rays without an active central engine. While hadronic interactions can account for bright gamma-ray emission from nearby clouds, the direct detection of MQRs remains challenging because their intrinsic emission is expected to be extended and of low surface brightness. In this work, we explore the broadband emission of MQRs by focusing on the leptonic component confined within the cocoon and on particle interactions in the shocked shell surrounding it. We model the injection and time-dependent transport of relativistic particles, including stochastic re-acceleration driven by internal turbulence, treated as a second-order Fermi process. We consider sub-Eddington and super-Eddington microquasar systems and compute the resulting non-thermal emission from radio to gamma-ray energies, together with the thermal soft X-ray emission produced in the shocked shell. In the super-Eddington case, the intrinsic emission reaches peak values of $νL_ν\sim 10^{35}-10^{36}\,{\rm erg\,s^{-1}}$, whereas sub-Eddington remnants are typically several orders of magnitude fainter. At 1.3 GHz, the modeled cocoon surface brightness is of order $Σ_ν\sim 10^{-19}\,{\rm W\,m^{-2}\,Hz^{-1}\,sr^{-1}}$ for young powerful remnants and decreases rapidly as the remnant evolves. We find that the direct detectability of MQRs is therefore controlled mainly by surface brightness rather than by integrated luminosity. Powerful remnants may be detectable as extended synchrotron radio cocoons and shell-dominated soft X-ray structures, whereas sub-Eddington remnants are expected to be much harder to identify directly. Our results suggest that MQRs may constitute a hidden population of extended Galactic non-thermal sources.
