Joint analysis of gravitational-wave and electromagnetic data of mergers: breaking an afterglow model degeneracy in GW170817 and in future events
Joint analysis of gravitational-wave and electromagnetic data of mergers: breaking an afterglow model degeneracy in GW170817 and in future events
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DOI：
10.1093/mnras/stad1728
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发表时间：
2022-12
影响因子：
4.8
通讯作者：
G. Gianfagna;L. Piro;F. Pannarale;H. van Eerten-H.-van Eerten-2125930852;F. Ricci;G. Ryan;E. Troja
中科院分区：
文献类型：
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作者：
G. Gianfagna;L. Piro;F. Pannarale;H. van Eerten-H.-van Eerten-2125930852;F. Ricci;G. Ryan;E. Troja
2017年8月17日，Advanced LIGO和Virgo观测到GW 170817，这是来自双中子星星合并的第一个引力波信号。随后是一个短持续时间的伽马射线暴，GRB 170817 A，以及一个非热余辉发射。在这项工作中，实现了电磁（EM，具体地说，余辉）和GW域的组合同时拟合，既使用GW独立分析的后验分布作为先验分布来单独处理EM数据，又同时拟合EM和GW域。这些方法在数学上一致，只要GW分析的实际后验而不是近似值用作EM分析的先验。我们将视角θv视为两个域之间的共享参数。在使用高斯结构射流的余辉建模中，该参数和射流核心角θc是相关的，导致其值的高度不确定性。联合EM + GW分析放松了这种退化，与仅EM拟合相比降低了不确定性。我们还将我们的方法应用于假设的GW 170817类似事件发生在下一个GW观测运行在140和70 Mpc。在70 Mpc的现有EM简并被打破，由于在分析中的GW域的列入。在140 Mpc时，由于在余辉上升阶段缺乏检测，仅EM拟合不能约束θv和θc。将GW数据合并到分析中会导致对θv的约束更严格，但θc仍不受约束，需要具有更高灵敏度的仪器，如Athena。
On 2017 August 17, Advanced LIGO and Virgo observed GW170817, the first gravitational-wave (GW) signal from a binary neutron star merger. It was followed by a short-duration gamma-ray burst, GRB 170817A, and by a non-thermal afterglow emission. In this work, a combined simultaneous fit of the electromagnetic (EM, specifically, afterglow) and GW domains is implemented, both using the posterior distribution of a GW standalone analysis as prior distribution to separately process the EM data, and fitting the EM and GW domains simultaneously. These approaches coincide mathematically, as long as the actual posterior of the GW analysis, and not an approximation, is used as prior for the EM analysis. We treat the viewing angle, θv, as shared parameter across the two domains. In the afterglow modelling with a Gaussian structured jet this parameter and the jet core angle, θc, are correlated, leading to high uncertainties on their values. The joint EM + GW analysis relaxes this degeneracy, reducing the uncertainty compared to an EM-only fit. We also apply our methodology to hypothetical GW170817-like events occurring in the next GW observing run at ∼140 and 70 Mpc. At 70 Mpc the existing EM degeneracy is broken, thanks to the inclusion of the GW domain in the analysis. At 140 Mpc, the EM-only fit cannot constrain θv nor θc because of the lack of detections in the afterglow rising phase. Folding the GW data into the analysis leads to tighter constraints on θv, still leaving θc unconstrained, requiring instruments with higher sensitivities, such as Athena.