在中子星合并和伽马射线暴中由R过程加热引起的后退吸积停止
Fallback Accretion Halted by R-process Heating in Neutron Star Mergers and Gamma-Ray Bursts
摘要：
具有macronova/kilonova的引力波事件GW 170817表明，两颗中子星的合并产生了具有放射性的物质，包括$r$过程的核合成。一部分喷出物不可避免地落回中心物体，可能为短伽马射线暴（sGRB）的长期活动提供动力，例如延长和平台发射。我们调查的回退吸积与$r$过程加热进行一维流体动力学模拟和开发一个半解析模型。我们发现，通常的回落率$dM/dt \propto t^{-5/3}$停止加热，因为压力梯度加速喷出物超过逃逸速度。抑制是陡峭的比Chevalier的幂律模型，通过邦迪吸积在一个转身半径。特征停止时间尺度为$\sim 10^5$ --类似GW 170817的$r$过程加热的$10^9$秒，其足够长以继续sGRB的持久发射。停止时间刻度对$r$过程的不确定性敏感。未来对回退停止的观测可能会限制年尺度上的$r$过程加热。
英文摘要：
The gravitational wave event GW170817 with a macronova/kilonova shows that a merger of two neutron stars ejects matter with radioactivity including $r$-process nucleosynthesis. A part of the ejecta inevitably falls back to the central object, possibly powering long-lasting activities of a short gamma-ray burst (sGRB), such as extended and plateau emissions. We investigate the fallback accretion with the $r$-process heating by performing one-dimensional hydrodynamic simulations and developing a semi-analytical model. We show that the usual fallback rate $dM/dt \propto t^{-5/3}$ is halted by the heating because pressure gradients accelerate ejecta beyond an escape velocity. The suppression is steeper than Chevalier's power-law model through Bondi accretion within a turn-around radius. The characteristic halting timescale is $\sim 10^5$--$10^9$ sec for the GW170817-like $r$-process heating, which is long enough to continue the long-lasting emission of sGRBs. The halting timescale is sensitive to the uncertainty of the $r$-process. Future observation of fallback halting could constrain the $r$-process heating on the year scale.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
