千新星(并合新星)研究回顾

中子星-中子星或中子星-黑洞的并合可以导致强烈的高频引力波辐射,同时它们也可以通过向外抛射物质发出多种类型的电磁辐射信号,因而是当前多信使天文学研究的主要对象之一.在各种电磁辐射信号中,由抛射物所发出的热暂现源辐射被称为千新星,或可更广义地称为并合新星,其辐射能量来源主要是抛射物中放射性重元素的衰变和中心并合产物的持续能量输出(如自转能损).这种现象最早由Li和Paczynski在1998年从理论上预言提出,并最终在2017年的引力波事件GW170817中被观测证实.千新星(并合新星)观测在GW170817事件中发挥了关键性的电磁对应体作用,帮助人们精确定位引力波信号、证认其天体物理起源乃至限制并合产物的性质.从宇宙中重元素的起源这一研究背景出发,循着历史发展的脉络,分别对千新星(并合新星)模型的提出、发展、并合产物的性质、相关候选体的发现以及GW170817引力波事件等不同的研究阶段和研究专题进行简要的回顾,以梳理这一方向上研究思路的历史变迁,展现理论和观测的相互作用及其对研究进程的影响和促进.

A Brief Review on Kilonovae or Mergernovae

While mergers of neutron star-neutron star and neutron star-black hole binaries can radiate intense high-frequency gravitational waves(GWs),they can also produce various electromagnetic emission by ejecting material outwards.Therefore,these merger events are the most important targets of current multi-messenger astronomical studies.The thermal transient emission from a merger ejecta is called a kilonova or,more generally,a mergernova,which is powered by the radioactive decays of r-process elements,and the energy injection from the central merger product.This phenomenon was first predicted theoretically by Li and Paczynski in 1998,and confirmed by the optical-infrared observations in the GW170817 event in 2017.As a result,the kilonova/mergernova observation had played a crucial role in locating GW170817,identifying its astrophysical origin,and even constraining the nature of the merger product of this event.This paper briefly reviews the primary progress of kilonova/mergernova researches,including the initiative,improvements,and developments of the model and the observational discoveries of candidates and the optical electromagnetic counterpart of GW170817.