[论文解读] Detection of Gravitational Waves using Pulsar Timing

R. N. Manchester|arXiv (Cornell University)|Apr 21, 2010

Pulsars and Gravitational Waves Research参考文献 1被引用 6

一句话总结

本文提出利用脉冲星时标阵（Pulsar Timing Array, PTA）通过测量天空中毫秒脉冲星的关联到达时间残差，探测来自超大质量黑洞双星的引力波（GWs）。在当前帕克斯脉冲星时标阵（Parkes Pulsar Timing Array, PPTA）的精度水平下，结合未来国际脉冲星时标阵（International Pulsar Timing Array, IPTA）和平方千米阵（Square Kilometre Array, SKA）的改进，若当前模型正确，预计在几年内可探测到随机引力波背景。

ABSTRACT

Pulsars are very stable clocks in space which have many applications to problems in physics and astrophysics. Observations of double-neutron-star binary systems have given the first observational evidence for the existence of gravitational waves (GWs) and shown that Einstein's general theory of relativity is an accurate description of gravitational interactions in the regime of strong gravity. Observations of a large sample of pulsars spread across the celestial sphere forming a "Pulsar Timing Array" (PTA), can in principle enable a positive detection of the GW background in the Galaxy. The Parkes Pulsar Timing Array (PPTA) is making precise timing measurements of 20 millisecond pulsars at three radio frequencies and is approaching the level of timing precision and data spans which are needed for GW detection. These observations will also allow us to establish a "Pulsar Timescale" and to detect or limit errors in the Solar System ephemerides used in pulsar timing analyses. Combination of PPTA data with that of other groups to form an International Pulsar Timing Array (IPTA) will enhance the sensitivity to GWs and facilitate reaching other PTA goals. The principal source of GWs at the nanoHertz frequencies to which PTAs are sensitive is believed to be super-massive binary black holes in the cores of distant galaxies. Current results do not signficantly limit models for formation of such black-hole binary systems, but in a few years we expect that PTAs will either detect GWs or seriously constrain current ideas about black-hole formation and galaxy mergers. Future instruments such as the Square Kilometre Array (SKA) should not only detect GWs from astrophysical sources but also enable detailed studies of the sources and the gravitational theories used to account for the GW emission.

研究动机与目标

• 通过网络化精确计时的毫秒脉冲星实现引力波的直接探测。
• 通过双星脉冲星计时检验广义相对论在强场区域的适用性。
• 建立基于脉冲星的时间标准，并探测太阳系星历中的误差。
• 通过整合全球PTA合作组织的数据，提升对引力波背景的探测灵敏度。
• 为未来利用SKA等下一代仪器探测单个引力波源并实现详细源特征分析做好准备。

提出的方法

• 在多个射电频率上对20颗毫秒脉冲星进行长期、高精度的计时测量。
• 分析脉冲星天球阵列中的到达时间残差，以探测由经过的引力波引起的关联偏差。
• 应用互相关技术，识别在脉冲星对之间具有特征信号的随机引力波背景。
• 将多个国际PTA团队的数据整合至国际脉冲星时标阵（IPTA），以提高灵敏度并减少系统误差。
• 建立超大质量黑洞双星和宇宙弦等来源的预期引力波信号模型，以设定灵敏度阈值。
• 利用模拟评估基于脉冲星分布和信噪比的源定位精度。

实验结果

研究问题

• RQ1 脉冲星时标阵能否探测到来自星系核心中超大质量黑洞双星产生的随机引力波背景？
• RQ2 利用脉冲星阵列，引力波源的天球位置可被多准确地定位？
• RQ3 单个脉冲星的计时不规则性在多大程度上限制了引力波的探测？
• RQ4 当前及未来仪器（如SKA）对单个引力波源的预期灵敏度如何？
• RQ5 脉冲星计时与太阳系星历中的系统误差对引力波探测产生何种影响？

主要发现

• 帕克斯脉冲星时标阵（Parkes Pulsar Timing Array, PPTA）正接近实现对随机引力波背景正向探测所需的计时精度与数据跨度。
• 当前的脉冲星计时限制已对通过引力波辐射形成中等质量黑洞的模型构成严重约束。
• 来自超大质量双星黑洞的随机引力波背景，预计会在与轨道周期相当的数据跨度内，产生幅度在5至50纳秒之间的关联到达时间残差。
• 模拟结果表明，PPTA在南半球的脉冲星分布可实现半功率波束宽度为15°–20°的源定位，且随着天空覆盖范围的提升而进一步改善。
• 国际脉冲星时标阵（International Pulsar Timing Array, IPTA）将显著提升对引力波的探测灵敏度，并改善系统误差的抑制能力。
• 平方千米阵（Square Kilometre Array, SKA）预计将以高保真度探测到随机与单个引力波源，从而实现对源及其辐射特性的详细研究。