Search for gravitational waves from low mass compact binary coalescence in LIGO’s sixth science run and Virgo’s science runs 2 and 3

We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and $25M_{\odot }$; this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are $1.3\times {10}^{-4}$, $3.1\times {10}^{-5}$, and $6.4\times {10}^{-6}{\mathrm{Mpc}}^{-3}{\mathrm{yr}}^{-1}$, respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge.

DOI: http://dx.doi.org/10.1103/PhysRevD.85.082002

Figure 1

Typical detector strain noise spectral density for the LIGO S6 and Virgo VSR2/3 runs. From lowest to highest at 10²  Hz, the curves are for the H1, L1, and V1 detectors.

Figure 2

Inspiral horizon distance versus the total mass of equal-mass binaries from S5/VSR1 and S6/VSR2/VSR3. The horizon distance is the distance at which an optimally located and oriented binary would produce an expected signal-to-noise ratio of 8. The figure shows the best sensitivity achieved by each detector during the runs.

Figure 3

The cumulative rate of events with chirp mass 3.48≤M/M_⊙<7.40 coincident in the H1 and L1 detectors, seen in four months of data around the September 16 candidate, as a function of the threshold ranking statistic ρ_c. The blue triangles show coincident events. Black dots show the background estimated from 100 time-shifts. Black crosses show the extended background estimation from all possible 5 sec shifts on this data restricted, for computational reasons, to only the tail of loudest events. The gray dots and crosses show the corresponding background estimates when 8 sec of data around the time of the candidate are excluded. Gray shaded contours show the 1-5σ (dark to light) consistency of coincident events with the estimated background including the extended background estimate, for the events and analysis time shown, including the candidate time. This event was later revealed to have been a blind injection.

Figure 4

The marginalized upper limits as a function of mass. The top plot shows the limit as a function of total mass M, using a distribution uniform in m₁ for a given M. The lower plot shows the limit as a function of the black hole mass, with the neutron star mass restricted to the range 1–3M_⊙. The light gray bars indicate upper limits from previous searches. The dark bars indicate the combined upper limits including the results of this search.

Figure 5

Comparison of CBC upper limit rates for BNS, NSBH, and BBH systems. The light gray regions display the upper limits obtained in the S5/VSR1 analysis; dark gray regions show the upper limits obtained in this analysis, using the S5/VSR1 limits as priors. The new limits are up to a factor of 1.4 improvement over the previous results. The lower (blue hatched) regions show the spread in the astrophysically predicted rates, with the dashed-black lines showing the realistic estimates [5]. Note: in Ref. 5, NSBH and BBH rates were quoted using a black hole mass of 10M_⊙. We have therefore rescaled the S5 and S6 NSBH and BBH upper limits in this plot by a factor of (M₅/M₁₀)^5/2, where M₁₀ is the chirp mass of a binary in which the black hole mass is 10M_⊙ and M₅ is the chirp mass of a binary in which the black hole mass is 5M_⊙.