[论文解读] The kilonova of GW190425-like events

C. Barbieri, O. S. Salafia+3 more|arXiv (Cornell University)|Feb 21, 2020

Pulsars and Gravitational Waves Research参考文献 15被引用 11

一句话总结

本文针对GW190425类事件建立千新星光变曲线模型，表明黑洞-中子星双星系统产生的千新星比双中子星系统更明亮，原因在于喷射物质质量更高以及黑洞自旋效应。引力波信号中的啁啾质量和光度距离可为电磁波后续观测提供支持，以区分双星系统的组成，尤其在天区定位不精确时更为有效。

ABSTRACT

GW190425 is the newly discovered compact object binary coalescence consistent with a neutron star-neutron star merger, with a chirp mass of $1.44\pm0.02M_\odot$. No electromagnetic counterpart is firmly associated with this event, due to the poorly informative sky localisation and larger distance, compared to GW/GRB170817. The detection of the gravitational wave signal alone can not rule out the presence of a black hole in the binary. In this case, the system would host a neutron star and a very light stellar black hole, with a mass close to the maximum value for neutron stars. We show that the possible presence of such a black hole in GW190425 would produce a brighter kilonova emission with respect to the double neutron star case. Therefore in GW190425-like events more precisely localised, the identification of a kilonova could help distinguishing the nature of the merging system. The chirp mass is a key parameter when joint gravitational and electromagnetic observations are possible. The knowledge of its value could help conducting strategic electromagnetic follow-up campaigns that would enhance the probability to identify the nature of the binary and the host galaxy. For GW190425-like events, we construct kilonova light curve models, for both double neutron star and black hole-neutron star binaries, considering two equations of state both consistent with the observations of GW170817 and GW190425, and including black hole spin effects. We show that among the candidate counterparts of GW190425, all classified as supernovae, our models would exclude two events through their early $r$-band flux evolution. This illustrates that combining the chirp mass and luminosity distance information (provided by the GW signal) with a library of kilonovae light curves can help the electromagnetic follow up campaign, particularly for events with a poor sky localization.

研究动机与目标

• 确定包含中子星与极轻黑洞的GW190425类事件是否会产生与双中子星并合不同的千新星特征。
• 评估电磁波后续观测是否可通过千新星光变曲线区分中子星-中子星与黑洞-中子星系统。
• 评估引力波信号中的啁啾质量与光度距离在改善天区定位较差事件的电磁波后续观测目标选择方面的潜力。
• 检验GW190425候选对应体与千新星模型的一致性，特别是早期r波段流量演化特征。

提出的方法

• 基于与GW170817和GW190425观测一致的两种方程状态，为双中子星和黑洞-中子星双星构建千新星光变曲线模型。
• 在千新星模型中引入黑洞自旋效应，以评估其对喷射物质质量和光度的影响。
• 将引力波反演得到的啁啾质量与光度距离作为建模框架中的关键约束条件。
• 将预测的光变曲线与GW190425候选对应体的早期r波段流量观测值进行比较，包括被归类为超新星的源。
• 应用千新星模型库，基于流量演化评估每个候选体为真实千新星的可能性。

实验结果

研究问题

• RQ1 千新星光变曲线能否在GW190425类事件中区分双中子星与黑洞-中子星系统？
• RQ2 黑洞自旋与方程状态如何影响预测的千新星光度与光变曲线形状？
• RQ3 引力波信号中的啁啾质量与光度距离在多大程度上可提升电磁波后续观测的目标选择效率？
• RQ4 基于早期r波段流量演化，能否排除已知的GW190425候选对应体（如被归类为超新星的源）？

主要发现

• 在GW190425类事件中，黑洞-中子星双星系统产生的千新星辐射显著强于双中子星系统，原因在于喷射物质质量更高以及自旋效应。
• 引入黑洞自旋可提高预测的千新星光度，尤其在早期阶段，从而增强探测可能性。
• 两个先前被归类为超新星的GW190425候选对应体，因早期r波段流量演化与模型不一致而被排除。
• 结合引力波反演得到的啁啾质量与光度距离，可实现更精准的电磁波后续观测目标选择，提升对双星性质与宿主星系识别的准确性。