Abstract
Results are presented from a semicoherent search for continuous gravitational waves from a nearby neutron star candidate, Fomalhaut b, using data collected in the second observing run of Advanced LIGO. The search is based on a hidden Markov model scheme, capable of tracking signal frequency evolution from the star's secular spin down and stochastic timing noise simultaneously. The scheme is combined with a frequency domain matched filter ($\mathcal{F}$-statistic), calculated coherently over five-day time stretches. The frequency band 100-1000 Hz is searched. After passing the above-threshold candidates through a hierarchy of vetoes, one candidate slightly above the 1% false alarm probability threshold remains for further scrutiny. No strong evidence of continuous waves is found. We present the strain upper limits in the full frequency band searched at 90% confidence level.
Highlights
Gravitational waves (GWs), perturbations in spacetime that propagate at the speed of light, were first directly observed in 2015 when the Advanced Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO) detected a merging binary black hole system (GW150914) [1,2]
Results are presented from a semicoherent search for continuous gravitational waves from a nearby neutron star candidate, Fomalhaut b, using data collected in the second observing run of Advanced LIGO
Without strong evidence of continuous gravitational waves (CWs), we present the strain upper limits and astrophysical interpretation in Sec
Summary
Gravitational waves (GWs), perturbations in spacetime that propagate at the speed of light, were first directly observed in 2015 when the Advanced Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO) detected a merging binary black hole system (GW150914) [1,2]. Other types of GW sources that radiate at frequencies within the observational band of ground-based interferometers remain yet undetected, e.g., the persistent, well modeled, continuous gravitational waves (CWs) produced by isolated spinning neutron stars. The tracking scheme has its origins in engineering and has recently been used in many CW searches (e.g., [12,15,26,27,28,29]) In this search, we assume that the signal frequency evolution is dominated by the star’s secular spin-down, allowing for minor stochastic timing noise, as the star is an isolated source (cf the signal evolution is expected to be dominated by timing noise if the source is in an accreting binary system).
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