Bachelor thesis defense by Frederik Aaboe Andersen

Title: Detection of continuous gravitational waves from fast-spinning neutron stars

Abstract:
This thesis explores a novel technique for detecting continuous gravitational wave signals, specifi- cally from rapidly spinning, asymmetric, isolated neutron stars, or pulsars. As these waves emitted by pulsars traverse the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, they induce minute perturbations in the fabric of space-time, consequently manifesting as periodic modulations in the strain data.

The strain data harnessed in this study is publicly accessible via the Gravitational Wave Open Science Center (GWOSC). Preparing the data entails performing a Short-time Fourier transform in Python using the GWpy package. Post-transformation, the data undergoes analysis using a search method that incorporates both the stack-slide method and the differential evolution algorithm.

The crux of this thesis lies in determining the sensitivity of our detection method. This is accomplished by using the PyFstat package to introduce synthetic signals of varying amplitudes into the LIGO strain data, thus allowing us to gauge the range of amplitudes our method can effectively detect. The smallest detectable amplitude thus serves as an estimate of our signal sensitivity. The result of this analysis indicates that the smallest detectable amplitude is:
h0 = (1.0 ± 0.5) · 10^−26. This yields a signal-to-noise-ratio of: (2 ± 1) · 10^−3. This ratio is sufficient for the measurement of authentic continuous gravitational wave signals.