We introduce a new capability of the Neil Gehrels Swift Observatory, dubbed “continuous commanding,” that achieves 10 s latency response time on orbit to unscheduled target-of-opportunity requests received on the ground. We show that this will allow Swift to respond to premerger (early-warning) gravitational-wave (GW) detections, rapidly slewing the Burst Alert Telescope (BAT) across the sky to place the GW origin in the BAT field of view at or before merger time. This will dramatically increase the GW/gamma-ray burst (GRB) codetection rate and enable prompt arcminute localization of a neutron star merger. We simulate the full Swift response to a GW early-warning alert, including input sky maps produced at different early-warning times, a complete model of the Swift attitude control system, and a full accounting of the latency between the GW detectors and the spacecraft. 60 s of early warning can double the rate of a prompt GRB detection with arcminute localization, and 140 s guarantees observation anywhere on the unocculted sky, even with localization areas ≫1000 deg². While 140 s is beyond current GW detector sensitivities, 30–70 s is achievable today. We show that the detection yield is now limited by the latency of LIGO/Virgo cyberinfrastructure and motivate a focus on its reduction. Continuous commanding has been integrated as a general capability of Swift, significantly increasing its versatility in response to the growing demands of time-domain astrophysics. We demonstrate this potential on an externally triggered fast radio burst (FRB), slewing 81° across the sky, and collecting X-ray and UV photons from the source position <150 s after the trigger was received from the Canadian Hydrogen Intensity Mapping Experiment, thereby setting the earliest and deepest such constraints on high-energy activity from nonrepeating FRBs. The Swift Team invites the community to consider and propose novel scientific applications of ultra-low-latency UV, X-ray, and gamma-ray observations.

中文翻译：

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实时快速追逐天空中的引力波


我们引入了 Neil Gehrels Swift 天文台的一项新功能，称为“连续指挥”，该功能可在轨道上对地面收到的计划外机会目标请求实现 10 秒的延迟响应时间。我们表明，这将使 Swift 能够响应合并前（早期预警）引力波 （GW） 探测，在天空中快速旋转爆发警报望远镜 （BAT），以在合并时间或之前将 GW 原点置于 BAT 视场中。这将大大提高 GW/伽马射线暴 （GRB） 共探测率，并实现中子星合并的快速弧分定位。我们模拟了 Swift 对 GW 预警警报的完整响应，包括在不同预警时间生成的输入天空图、Swift 姿态控制系统的完整模型，以及 GW 探测器和航天器之间延迟的完整核算。60 秒的早期预警可以将弧分定位的 GRB 快速检测率提高一倍，而 140 秒可以保证在未掩蔽的天空中的任何地方进行观测，即使是 ≫1000 度² 的定位区域也是如此。虽然 140 秒超出了当前 GW 探测器的灵敏度，但今天可以达到 30-70 秒。我们表明，检测率现在受到 LIGO/Virgo 网络基础设施延迟的限制，并促使人们专注于减少其减少。连续指挥已被整合为 Swift 的一项通用功能，显著提高了其多功能性，以响应时域天体物理学日益增长的需求。 我们在外部触发的快速射电暴 （FRB） 上展示了这种潜力，在天空中旋转 81°，并在从加拿大氢强度映射实验接收到触发后从源位置 <150 s 收集 X 射线和紫外线光子，从而为非重复 FRB 的高能活动设定了最早和最深的此类限制。Swift 团队邀请社区考虑并提出超低延迟 UV、X 射线和 γ 射线观测的新颖科学应用。