Searches for Continuous Gravitational Waves From Nine Young Supernova Remnants

Abstract

We describe directed searches for continuous gravitational waves (GWs) in data from the sixth Laser Interferometer Gravitational-wave Observatory (LIGO) science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the remnants are associated with non-pulsing suspected neutron stars. One targetʼs parameters are uncertain enough to warrant two searches, for a total of 10. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering -statistic. We found no evidence of GW signals. We set 95% confidence upper limits as strong (low) as 4 × 10 −25 on intrinsic strain, 2 × 10 −7 on fiducial ellipticity, and 4 × 10 −5 on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes.

Consequences of a strong phase transition in the dense matter equation of state for the rotational evolution of neutron stars

“…If the collapse is not entirely axisymmetric, the final configuration may retain an asymmetry, thus creating a rotating NS that spins down while continuously emitting the almost-monochromatic GWs. Such objects are among the prime astrophysical targets of the Advanced LIGO and Advanced Virgo interferometric detectors (see the demonstration of search pipelines used on the initial LIGO and initial Virgo detector data, e.g., Aasi et al 2014aAasi et al ,b, 2015.…”

Cross-correlation search for continuous gravitational waves from a compact object in SNR 1987A in LIGO Science run 5

“…Self-correlation terms are not included in (24) and (25). Again, we stress that µ and σ in (24) and (25) are not derived from (22) and (23) simply by dividing the latter equations by σ ρ and σ 2 ρ respectively. The PDF of ρ/σ ρ is not truly Gaussian for pure noise, if dependent pairs are included [69].…”

“…Data from S5 and S6 have been analysed in several searches for continuous wave sources in supernova remnants targeting specific, known sources like the Crab pulsar [16][17][18], Cassiopeia A [19,20], other young pulsars with radio or X-ray ephemerides [18,21], and young supernova remnants [22]. Broadband, all-sky searches have also been carried out for unknown sources, some of which may turn out post-discovery to reside in supernova remnants [23][24][25].…”

Search for continuous gravitational waves from neutron stars in globular cluster NGC 6544

“…An alternate data selection scheme [22,25], which takes detector duty cycle into account, is to maximize the figure of merit…”

“…Other directed searches have since followed in its footsteps, using different data analysis methods, for supernova 1987A and unseen neutron stars near the galactic Center [21,24]. Most methodologically similar to this search and the S5 Cas A search was a recent search for nine supernova remnants [25], which also used fully coherent integration over observation times on the order of 10 days.…”