Low-latency analysis pipeline for compact binary coalescences in the advanced gravitational wave detector era

Abstract

Gravitational wave detection is eagerly expected as one of the major discoveries of the next decade. A worldwide effort is currently underway, building ever-more-sensitive detectors and developing more powerful data-analysis tools. Continuous gravitational waves (CWs) are a promising class of signals for advanced detectors, and a particularly interesting type of CW sources are neutron stars in low-mass X-ray binaries, with Scorpius X-1 being the most remarkable representative. We describe the details of a project aimed to perform directed searches for CWs from binary systems. We use a search algorithm based on coherently computing a maximum likelihood statistic for a bank of signal templates, and then incoherently summing this statistic over the segments in which the entire data set has been previously split. The current strategy strongly relies on the derivation of precise analytic expressions for the (coherent and semicoherent) phase metrics of CW sources in low-eccentricity binary systems, for the two regimes of long and short segments compared to the orbital period. As an application of the metric template expressions, we estimate the optimal achievable sensitivity of an Ein-stein@Home directed search for Scorpius X-1, under the assumption of sufficiently small spin wandering, and using data from the upcoming advanced detectors. We find that such a search would be able to beat the torque-balance level up to a frequency of 500-600 Hz, if orbital eccentricity is well-constrained, and up to a frequency of ∼160-200 Hz for more conservative assumptions about the uncertainty on orbital eccentricity.

Upper Limits on the Rates of Binary Neutron Star and Neutron Star–black Hole Mergers From Advanced Ligo’s First Observing Run

“…The online compact binary coalescence (CBC) search of the O1 data also consisted of two analyses; an online version of GstLAL (Messick et al 2016) and mbta (Adams et al 2016). For detailed descriptions of the mbta analysis we refer the reader to Beauville et al (2008), Abadie et al (2012a), and Adams et al (2016).…”

“…For detailed descriptions of the mbta analysis we refer the reader to Beauville et al (2008), Abadie et al (2012a), and Adams et al (2016). The bank of waveform filters used by GstLAL up to 2015 December 23-and by mbta for the duration of O1-targeted systems that contained at least one NS.…”

Fast localization of coalescing binaries with a heterogeneous network of advanced gravitational wave detectors

“…This study is based on simulated data previously generated in the context of [13] and analyzed in order to derive the sky localization performance obtained when post-processing MBTA triggers reported in [8]. The data set features 248 simulated signals from binary neutron star (BNS) sources, injected into simulated detector noise designed to match the expected initial performance of the Advanced LIGO detectors [13].…”

“…Events with sufficient significance are then communicated to the astronomy community for follow-up observations. The LIGO-Virgo Collaboration has been performing low-latency CBC searches with several pipelines: multi-band template analysis (MBTA) [8], GstLAL [9] and pyCBC Live [10]. Candidate events are uploaded to the GraceDb [11] and processed through the Bayesian rapid localization algorithm (Bayestar) [12] for fast position reconstruction, which generates probability sky maps.…”

Ranking candidate signals with machine learning in low-latency searches for gravitational waves from compact binary mergers

“…Up to date, several pipelines [11][12][13][14][15][16] for the low-latency GW search have been developed and conducted to search GW signals by analyzing the time series GW data in real-time. The common goal of these pipelines is identifying a candidate GW event as soon as possible.…”