NEW APPLICANT: Enabling rapid observation of compact binary mergers with a network of gravitational-wave observatories

引力波是爱因斯坦广义相对论中最引人注目的预言之一。这些可以被认为是时空结构中以光速传播的涟漪。引力波是由非球对称的加速质量发出的，比如两个黑洞或相互环绕的中子星。引力波很难探测到，但在过去的几年里，大型天文台，包括高级LIGO，高级处女座和KAGRA，已经达到了观测引力波的必要灵敏度。2015年9月观测到的第一个引力波信号是由两个质量约为太阳35倍的黑洞在大约10亿光年远的地方碰撞产生的。从那以后，又观察到9次双黑洞合并。迄今为止，引力波天文学的最高成就是在2017年8月观测到两颗合并的中子星。这个信号很特别，因为它是费米天文台同时观测到的伽马射线暴，然后，在向天文学家释放引力波天空定位区域之后，通过电磁波谱观测到。“多信使”天文学——用多个“信使”观测源，如引力波、光子、中微子或宇宙射线——的潜力是显著的。我们可以在最极端的环境中探索爱因斯坦理论的有效性。我们可以对宇宙加速的速度进行独立的测量。我们可以探测中子星深处物质的本质，那里的密度非常大，一茶匙的物质相当于地球上一座山的重量。然而，所有这些都需要我们实际观察这些引力波信号，而且要足够快，以便我们能够提醒外部天文学家寻找一致的信号。在这笔拨款中，我们将开发方法来快速搜索来自高级LIGO、高级Virgo和KAGRA的数据，以观察合并致密物体的引力波特征。我们将确保这些观测迅速定位于天空，并将这些信息迅速传达给外部观测者。我们还将开发技术来进一步提高这些搜索的灵敏度，使我们能够更深入地挖掘噪音，并观察到迄今为止尚未观察到的新型紧凑双星合并。我们还将利用观测的天体物理学潜力。我们将研究双黑洞系统是由双星系统形成的，在双星系统中，两颗恒星都经历了一次超新星爆炸，形成了一对绕轨道运行的黑洞，还是两个黑洞是单独形成的，后来在一些密集的环境中由于相互作用而走到了一起。我们还将探索中子星核心的物质行为，中子星是宇宙中最极端的环境之一。

Gravitational waves are one of the most remarkable predictions of Einstein's General Theory of Relativity. These can be thought of as ripples in the fabric of spacetime propagating at the speed of light. Gravitational waves are emitted by non-spherically symmetric accelerated masses, such as two black holes or neutron stars orbiting each other. Gravitational waves are incredibly difficult to detect, but in the last years large-scale observatories, including Advanced LIGO, Advanced Virgo and KAGRA, have reached the necessary sensitivity to observe gravitational waves.The first gravitational-wave signal observed in September 2015 was produced by two black holes roughly 35 times the mass of our Sun colliding approximately one billion light years away. Since then nine additional binary black hole mergers have been observed. The crowning achievement of gravitational-wave astronomy to date was the observation of two merging neutron stars in August 2017. This signal was special because it was observed simultaneously as a gamma-ray burst by the Fermi observatory and then, following the release of the gravitational-wave sky localization region to astronomers, was observed across the electromagnetic spectrum.The potential of "multi-messenger" astronomy-observing sources with multiple "messengers", such as gravitational-waves, photons, neutrinos or cosmic rays-is remarkable. We can explore the validity of Einstein's theory in one of the most extreme environments possible. We can make an independent measurement of the rate at which the Universe is accelerating. We can probe the nature of matter deep within a neutron star, where it is so dense that 1 teaspoon of material weighs as much as a mountain on the Earth.However, all of this requires us to actually observe these gravitational-wave signals, and to do it quickly enough that we can alert external astronomers to search for a coincident signal. In this grant we will develop methods to promptly search data from Advanced LIGO, Advanced Virgo and KAGRA to observe the gravitational-wave signature of merging compact objects. We will ensure that such observations are rapidly localized on the sky and that this information is rapidly communicated to external observers. We will also develop techniques to further improve the sensitivity of these searches, allowing us to dig deeper into the noise, and to observe new types of compact binary mergers that have not been observed to date.We will also exploit the astrophysical potential of our observations. We will investigate if double black hole systems form from binary star systems, where both stars have gone through a supernova resulting in a pair of orbiting black holes, or if the two black holes formed in isolation and were later came together as a result of interactions in some dense environment. We will also look to probe the behaviour of matter at the core of neutron stars, one of the most extreme environments in the Universe.