Prospects for Detection of Continuous Gravitational Waves From Rotating Neutron Stars

Le résumé fourni par la source

The year 2015 is marked as the beginning of gravitational wave astronomy, as the signal originating from two black holes merging ≈1.3 billion light-years away from us struck Earth, leaving a tiny but measurable mark on both detectors of the Advanced LIGO facility, which had turned operational only a couple of weeks prior to this event. We now know gravitational waves exist, and laser gravitational wave interferometers are capable of detecting them. We also know that our computational techniques are suitable for extracting extremely valuable information on the nature and phenomenology of the sources of gravitational wave radiation. Despite the sensational pace at which the field has grown since its inception, the picture is far from complete. Of all types of gravitational waves that could plausibly occur in nature, only burst signals stemming from merging compact objects (for the most part, black holes) have been detected. Among others, continuous gravitational waves continue to elude detection. This work focuses on this type of signal. In this thesis, we discuss the prospects for detecting continuous gravitational waves from Galactic neutron stars. We consider different manifestations of neutron stars, thereby encompassing a broad range of signal frequencies. To this end, we consider both gravitational wave detectors currently in operation and those that will be commissioned in the future, deploying robust observation-based detectability criteria. Our approach varies with respect to the case study. In our first work, we model the Galactic neutron star population using an ab initio approach, consistently accounting for the non-trivial interplay between the various quantities that characterise neutron stars and the gravitational signals they emit. In a second work, we aim to demonstrate the scientific relevance of continuous gravitational wave emission from highly magnetised neutron stars, considering the band below 20 Hz, which will soon be available thanks to both ground-based and space-based facilities. In a third and final study, we investigate the evolution of the low-mass X-ray binary system Scorpius X-1, which has long been considered one of the most promising systems for the emission of continuous gravitational waves. We study the influence that the evolutionary history of the binary system has on the emission of continuous gravitational waves, demonstrating how radical this can sometimes be. We also quantify the probability of detecting continuous gravitational waves from Scorpius X-1 in different astrophysical scenarios.

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