[论文解读] Modeling Supernova-like Explosions Associated with Gamma-ray Bursts with Short Durations

S. R. Kulkarni|arXiv (Cornell University)|Oct 10, 2005

Gamma-ray bursts and supernovae参考文献 1被引用 93

一句话总结

本文提出，短硬伽马射线暴（GRBs）可能伴随有微弱的、亚相对论性爆炸，称为巨新星，其能量来源可能是镍的放射性衰变或自由中子的衰变。研究发现，由中子衰变驱动的巨新星在暴发后数小时内至一天内可用当前的10米级望远镜探测到，为探究短GRB起源提供了关键观测途径；而由镍驱动的巨新星由于衰变 timescale 较长，需要更深度的观测。

ABSTRACT

There is now good evidence linking short-hard GRBs with both elliptical and spiral galaxies at relatively low redshifts, redshift of about 0.2. This contrasts with the average redshift of about 2 of long-duration events, which also occur only in star-forming galaxies. The diversity of hosts is reminiscent of type Ia supernovae, which are widely (but not universally) believed to originate from the coalescence of white dwarfs. By analogy, it has been postulated that short-hard bursts originate from neutron star mergers. Mergers, as well as stellar core-collapse events (type II SNe and long-duration GRBs) are accompanied by long-lived sub-relativistic components powered by radioactive decay of unstable elements produced in the explosion. It is therefore interesting to explore whether short duration events also have ejecta powered by radioactivity (i.e. that are supernova-like). Observations already inform us that any supernova like component in the first few well studied short hard bursts must be fainter than those typical of type Ia or core-collapse supernovae. Rather than refer to weaker supernova-like component as ``mini-super nova'', an etymologically indefensible term, I use the term {\it macronova}. I investigate the observability of macronovae powered by neutron decay and by radioactive Nickel. Separately, I note that a macronova will reprocess energetic emission arising from a long lived central source. I find that surprisingly interesting limits on the basic parameters of macronovae can be obtained provided observations are obtained with current 10-m class telescopes over a range of one hour to one day following the burst.

研究动机与目标

• 研究短硬伽马射线暴是否伴随有由放射性衰变驱动的、亚相对论性、类似超新星的爆炸（巨新星）
• 评估利用当前10米级望远镜探测巨新星的可行性，重点关注暴发后数小时至数天内的光学光曲线
• 评估巨新星的两种潜在能量来源：自由中子的衰变和放射性镍的衰变
• 探讨长寿命中心引擎通过与亚相对论性喷流相互作用，将辐射能重新处理为可观测辐射的作用
• 为巨新星提供一个理论框架，涵盖光子-物质平衡、伽马射线透明度以及在低质量、高速喷流中的能量沉积

提出的方法

• 通过中子衰变和56Ni衰变的能量沉积建模巨新星光曲线，关注与观测窗口相关的时标
• 纳入光子生成、光子-物质平衡以及在低质量、高速喷流中的伽马射线能量沉积
• 计算喷流对伽马射线的透明度，这对低质量、快速膨胀的系统至关重要
• 在现实条件下评估可观测性，使用当前10米级望远镜，特别关注早期（1小时至1天）观测
• 比较中子驱动与镍驱动巨新星的可探测性，考虑衰变时标和光度演化差异
• 考虑长寿命中心源通过与慢速运动喷流相互作用，将辐射能重新处理为更长波长辐射的影响

实验结果

研究问题

• RQ1 由中子衰变驱动的巨新星是否可在短硬GRB发生后数小时内至一天内被当前10米级望远镜探测到？
• RQ2 喷流中放射性元素的衰变时标如何影响巨新星的可探测性？
• RQ3 长寿命中心引擎在多大程度上通过与亚相对论性喷流相互作用，将辐射能重新处理为可观测辐射？
• RQ4 光子-物质平衡和伽马射线透明度如何影响低质量、高速巨新星的可观测特性？
• RQ5 为何尽管能量输出相似，镍驱动的巨新星显著比中子驱动的更难探测？

主要发现

• 由中子衰变驱动的巨新星可在短硬GRB发生后数小时内至一天内被当前10米级望远镜探测到，提供了切实可行的观测路径
• 半衰期为900秒的中子衰变驱动巨新星可产生可探测信号，但若人为将衰变时间缩短至90秒，则无法探测
• 由于衰变时标较长，镍驱动的巨新星需要比当前可行深度更深的观测，才能提供有意义的约束
• 长寿命中心源通过亚相对论性喷流重新处理辐射能，可模拟或增强巨新星辐射，提供一种替代能量来源
• 喷流对伽马射线的透明度是决定可观测流量的关键因素，尤其对低质量、高速系统而言
• 巨新星的观测为短硬GRB起源提供了最直接的线索，仅次于未来的引力波探测