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The EMMEPH Prize for the best Bachelor thesis of 2020 has been awarded to Thomas Spieksma for his thesis “Constraining the electric charge of binary black holes and neutron stars through gravitational wave observations”. 

The EMMEPH Prize for the best Bachelor thesis is presented annually. This year, there were two prize winners, with Spieksma as one of them. Thomas Spieksma received the prize during the prize ceremony right after the EMMEPH 't Hooft Colloquium at September 30.

Research

Thomas Spieksma did his Bachelor research under the supervision of Professor Chris Van Den Broeck. The thesis studies gravitational waves emitted by binary systems consisting of neutron stars or black holes. Though both are expected to be electrically neutral to good approximation, general relativity does not prohibit either to possess net electric charge, and indeed there exist concrete mechanisms whereby some amount of excess charge might be acquired by a black hole. Spieksma first of all calculated the effect that charges would have on the orbital motion in a binary system, and what would be the imprint upon the gravitational waves that are emitted. With this in hand, he analysed LIGO-Virgo data containing the gravitational wave signals from five selected binary black hole mergers, and placed upper bounds on the amounts of charge that may have been present in them. Next he turned to radio telescope data for the binary pulsar PSR J0737-3039. The orbits of the two neutron stars in this binary are slowly decaying due to the emission of gravitational waves, and the rate at which this happens was used by Spieksma to also in this case place bounds on the amount of electric charge on the stars. Finally, by the mid-2030s a third-generation gravitational wave observatory called Einstein Telescope (which may be placed in the Netherlands) is expected to be operational, and this will enable much more accurate measurements on the signals from binary black hole mergers. Spieksma came up with projections for how stringent the upper bounds from Einstein Telescope will be – or, with a bit of luck, net electric charges on black holes might in fact be detected this way.