SPIIR online coherent pipeline to search for gravitational waves from compact binary coalescences

Qi Chu, Manoj Kovalam, Linqing Wen, Teresa Slaven-Blair, Joel Bosveld, Yanbei Chen, Patrick Clearwater, Alex Codoreanu, Zhihui Du, Xiangyu Guo, Xiaoyang Guo, Kyungmin Kim, Tjonnie G. F Li, Victor Oloworaran, Fiona Panther, Jade Powell, Anand S. Sengupta, Karl Wette, Xingjiang Zhu

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


This paper presents the Summed Parallel Infinite Impulse Response (SPIIR) pipeline used for public alerts during the third advanced LIGO and Virgo observation run (O3 run). The SPIIR pipeline uses infinite impulse response (IIR) filters to perform extremely low-latency matched filtering and this process is further accelerated with graphics processing units (GPUs). It is the first online pipeline to select candidates from multiple detectors using a coherent statistic based on the maximum network likelihood ratio statistic principle. Here we simplify the derivation of this statistic using the singular-value-decomposition (SVD) technique and show that single-detector signal-to-noise ratios from matched filtering can be directly used to construct the statistic. Coherent searches are in general more computationally challenging than coincidence searches due to extra search over sky direction parameters. The search over sky directions follows an embarrassing parallelization paradigm and has been accelerated using GPUs. The detection performance is reported using a segment of public data from LIGO-Virgo’s second observation run. We demonstrate that the median latency of the SPIIR pipeline is less than 9 seconds, and present an achievable road map to reduce the latency to less than 5 seconds. During the O3 online run, SPIIR registered triggers associated with 38 of the 56 nonretracted public alerts. The extreme low-latency nature makes it a competitive choice for joint time-domain observations, and offers the tantalizing possibility of making public alerts prior to the merger phase of binary coalescence systems involving at least one neutron star.

Original languageEnglish
Article number024023
Number of pages17
JournalPhysical Review D
Issue number2
Publication statusPublished - 15 Jan 2022


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