Presentasjon av masteroppgave: Øyvind Christiansen
Charged Black Hole Mergers: Emissions, Orbital Evolution, Gravitational Waveform and Observer Bias
Gravitational waveforms from mergers or close-encounters of astrophysical compact bodies provide a new and separate window into high energy physics and dark objects. Although there is a zoo of theoretical compact objects that the current detectors of this channel might be sensitive to, we still have not found anything we did not already expect, apart from slightly surprising high stellar mass black hole merger rates and small final spins, both of which are at slight tension with common binary system formation mechanisms. The reason why no such object has appeared in our data might be because we are not looking for them, detections typically being done using matched filtering – a statistical method requiring a highly precise theoretical prediction of the signal to dig it out of the noise. In this work we extend some of the analysis already done at lowest order to compact objects carrying some U(1) charge. We consider how the extra interaction and emission modifies the dynamics in the slow-inspiral regime and evolve the orbit until its merger phase. The circularisation is shown to be slightly weaker for orbits where the gauge-field dominates the back-reaction, though both here and in the standard gravitationally dominated emission do we expect to have mergers circularise by the time they enter detector sensitivity, given a large enough initial separation. We find the first correction from U(1) emission to the gravitational emission driven orbit, this rep- resenting the small charge limit, and find again the orbital evolution, which in turn gives us the gravitational waveform. Having the waveform, we consider how it would be interpreted in gravitational wave detectors where neutral signals are expected, or whether it would be detected at all, using the least squares method and matched filtering. We find, under some assumptions, that the projection onto neutral templates would bias a large mass, without a very large loss of signal. This would, together with previous research done in the field, point towards a possible explanation for both aforementioned curiosities in the detector data so far. Finally we present discussions on how the analysis might be extended to unbound encounters and mergers carrying electric and magnetic charges, presenting the O(v) order orbital dynamics and emissions for the latter.
Veileder: Professor David F. Mota, Institutt for teoretisk astrofysikk, UiO
Medveileder: Professor Jose Beltran Jimenez, University of Salamanca
Intern sensor: Professor Øystein Elgarøy, Institutt for teoretisk astrofysikk, UiO
Ekstern sensor: Professor Sigbjørn Hervik, Universitetet i Stavanger