发表机构
Tsung-Dao Lee Institute, Shanghai Jiao-Tong University; School of Astronomy and Space Science, Nanjing University; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education; Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn（李政道研究所，上海交通大学; 南京大学天文与空间科学学院; 现代天文学和天体物理学教育部重点实验室（南京大学）; 波恩大学赫尔姆霍兹射线与核物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过蒙特卡洛模拟工具GRB-offset重新建模双中子星并合偏移，发现偏移分布对物理要素敏感且存在简并性，表明仅凭观测偏移难以约束前身星和宿主星系性质。
AI 中文摘要
伽马射线暴（GRB）相对于其宿主星系的投影偏移是其物理起源的重要诊断指标，其中宿主星系的关联通常通过偶然重合概率来评估。然而，观测表明，在某些情况下，这种方法给出的宿主星系关联可能是不明确的。在本工作中，我们利用蒙特卡洛模拟进行受控数值实验，重新审视双中子星（DNS）并合偏移的建模。为了将第二颗超新星（SN）的动力学效应与上游双星演化的不确定性分离开来，我们对DNS的直接前身星进行参数化，并使用\texttt{galpy}在星系引力势中积分超新星后的轨迹。作为对先前种群合成计算的补充，我们的蒙特卡洛工具\texttt{GRB-offset}提供了一个轻量级框架，用于识别敏感性并揭示偏移建模中的简并性。利用\texttt{GRB-offset}，我们研究了以下物理要素：超新星物理（抛射质量和踢速度）、星系引力势（势形状、星系维里质量）、DNS诞生位置、恒星形成历史以及红移。我们的参考蒙特卡洛模拟给出的偏移分布对于束缚于宿主星系的DNS和未束缚的DNS分别在约30千秒差距和1000千秒差距处达到峰值，这敏感地依赖于所考虑的物理要素。给定的偏移可以由这些要素的各种组合产生，在解释观测偏移时引入了实质性的简并性。因此，仅凭观测到的偏移很难约束DNS前身星和宿主星系的性质。
英文摘要
The projected offset of a Gamma-Ray Burst (GRB) from its host galaxy is an important diagnostic of its physical origin, where the host associations are usually evaluated through chance-coincidence probabilities. However, as shown by observations, the host associations given by this approach may be ambiguous in some cases. In this work, we revisit the modelling of the offsets of double-neutron-star (DNS) mergers with controlled numerical experiments using Monte Carlo simulations. To isolate the dynamical effects of the second supernova (SN) from uncertainties in the upstream binary evolution, we parametrise the direct progenitor of DNSs and integrate the post-SN trajectories in galactic potentials using \texttt{galpy}. Complementary to previous population synthesis calculations, our Monte-Carlo tool, \texttt{GRB-offset}, provides a lightweight framework to identify sensitivities and expose degeneracies in offset modelling. With \texttt{GRB-offset}, we have investigated the following physical ingredients, supernova physics (ejected mass and kick velocity), galactic potential (potential shape, galaxy virial mass), DNS birth location, star formation history, and redshift. The offset distributions given by our reference Monte-Carlo simulation peak at around 30 kpc and 1000 kpc for the DNSs bound to and unbound from the host galaxy, which sensitively depends on the considered physical ingredients. A given offset can arise from various combinations of these ingredients, introducing substantial degeneracies when interpreting observed offsets. Therefore, an observed offset alone can hardly constrain the properties of the DNS progenitor and of the host galaxies.
Commentsaccepted by ApJ; The Monte Carlo tool constructed in this work, tailored for modelling GRB offsets with a focus on the dynamical effects of the second supernova event, is available at https://zenodo.org/records/22765322
