Realistic LIGO/Virgo/KAGRA observing scenarios based on O3 public alerts

Efforts to search for electromagnetic counterparts of gravitational-wave sources have intensified dramatically since the 2017 discovery a binary neutron star merger with an associated gamma-ray burst, optical/infrared kilonova, and panchromatic afterglow. Now, one LIGO/Virgo observing run later, there has not yet been a second secure identification of electromagnetic counterpart. This is not unexpected, and can be mostly explained by the localization uncertainty of events from LIGO and Virgo’s most recent, third observing run (“O3”). The official LIGO/Virgo observing scenarios fail to account for improvements in data analysis that allow LIGO/Virgo to detect fainter and hence worse-localized gravitational- wave sources, which increases the number of detections while decreasing the proportion of well-localized “gold-plated” events. Realistic forecasting of gravitational-wave localization performance is paramount because electromagnetic counterpart searches require large commitments of telescope time. We present simulations of the next several LIGO/Virgo/KAGRA observing runs that are based on the statistics of O3 public alerts.自2017年发现首个伴随伽马射线暴（gamma-ray burst）、光学/红外千新星（kilonova）及全波段余辉（panchromatic afterglow）的双中子星并合事件以来，搜寻引力波源电磁对应体的工作已显著强化。历经一轮激光干涉引力波天文台（LIGO）与室女座干涉仪（Virgo）观测运行后，目前尚未有第二例得到可靠证认的电磁对应体。这一结果并不出乎意料，其成因主要可归结为LIGO与Virgo第三轮观测运行（"O3"）中引力波事件的定位不确定性。LIGO/Virgo官方设定的观测场景未能涵盖数据分析技术的进步——这些进步使得LIGO/Virgo能够探测到更暗弱、因而定位精度更低的引力波源，这在提升探测总数量的同时，降低了高精度定位“金标准”事件的占比。对引力波定位性能开展贴合实际的预估至关重要，因为电磁对应体搜寻工作需要投入大量望远镜观测时长。我们基于O3公开警报的统计数据，对未来数轮LIGO/Virgo/KAGRA观测运行展开了模拟研究。