发表机构
Centro Brasileiro de Pesquisas Físicas; Universidade Federal do Espírito Santo（巴西物理研究中心; 圣埃斯皮里图联邦大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出星系核区致密双星经引力弹弓效应被弹射，可解释大偏移伽马射线暴的起源，数值模拟显示部分系统在超100千秒差距处并合。
AI 中文摘要
越来越多的伽马射线暴（GRB）在其宿主星系中心附近被观测到具有较大的投影偏移，有时可达数十千秒差距。当GRB与千新星相关联时，预期涉及至少包含一颗中子星的致密双星，偏移的原因可归因于中子星的诞生冲力。在本工作中，我们探索了一种替代机制：由中等质量黑洞或次级超大质量黑洞对宿主星系核区中的致密双星进行引力散射。我们特别考虑了中子星-中子星（NS-NS）、中子星-黑洞（NS-BH）和中子星-白矮星（NS-WD）双星群体，并分析了通过引力弹弓效应将束缚系统从核区弹射出去的过程。我们通过解析方法推导了双星存活的条件，并对遭遇后的速度进行了参数化。为了量化相关的并合偏移，我们在包含主超大质量黑洞、恒星成分和暗物质晕的宿主星系引力势中，对弹弓后双星质心轨迹进行了数值积分，同时考虑了椭圆型和旋涡型星系轮廓。我们的参数采样表明，NS-NS和NS-WD双星通常比NS-BH系统在离星系中心更远处并合，其中约30-45%的成功弹射在三维距离超过100千秒差距处并合；这些极端偏移的并合发生在弹射后约0.1-10吉年内。这些结果支持所分析的机制作为观测到的极端偏移瞬变源的候选通道。
英文摘要
A growing number of gamma-ray bursts (GRBs) have been observed at large projected offsets from the centres of their putative host galaxies, sometimes extending to several tens of kiloparsecs. When the GRB is associated with a kilonova, a compact binary with at least one neutron star is expected to be involved, and the cause of the offset can be attributed to the neutron star natal kick. In this work, we explore an alternative mechanism: the gravitational scattering of compact binaries populating the nuclear region of the host galaxy, by an intermediate-mass black hole or secondary supermassive black hole. We specifically consider populations of neutron star-neutron star (NS-NS), neutron star-black hole (NS-BH), and neutron star-white dwarf (NS-WD) binaries, and analyse the ejection of bound systems from the nuclear region through a gravitational-slingshot effect. We proceed analytically to derive the conditions for binary survival and to parametrise the post-encounter velocity. To quantify the associated merger offsets, we numerically integrate the post-slingshot trajectory of the binary centre-of-mass in host-galaxy potentials that include the primary SMBH, the stellar component, and the dark-matter halo, considering both elliptical-like and spiral-like galaxy profiles. Our parameter sampling shows that NS-NS and NS-WD binaries typically merge farther from the galactic centre than NS-BH systems, with approximately 30-45% of successful ejections merging at three-dimensional distances exceeding 100 kpc; these extreme-offset mergers occur within $\sim$0.1-10 Gyr after ejection. These results motivate the analysed mechanism as a candidate channel for observed extreme-offset transients.
Comments21 pages, 12 figures
