New discoveries on the horizon - gravitational-wave observatories have already observed 200 detection candidates
Researchers at the AEI contributed to this success.
During the ongoing fourth observing run (O4), the international network of the LIGO, Virgo and KAGRA gravitational-wave observatories identified 200 candidate signals. In previous observing runs, 90 signals have been identified. The new candidates are now being thoroughly investigated. They have also been immediately reported to astronomers worldwide via NASA's GCN Circulars. The scientific communities are now looking forward to exciting new information about black holes, neutron stars, and the evolution of our Universe.
Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) and at Leibniz University Hannover, including many PhD students and postdoctoral researchers, have contributed to this achievement.
AEI researchers developed sophisticated waveform models that were used to discriminate real cosmic sources from random fluctuations and terrestrial disturbances appearing in the detector. These models were used to detect and infer the peculiar properties, notably the masses, of GW230529 – the only event published so far out of the 200 candidates.
Another waveform model developed at the AEI that includes the effect of mode asymmetry and the resulting “kick” is used in the analysis. Some binary black hole systems do not emit gravitational waves symmetrically. This imparts a recoil velocity – also called a “kick” – to the remnant black holes formed from such mergers. Identifying such effects in the signals can help to obtain more astrophysical information about the black hole binaries.
Neural network-based parameter estimation methods developed at the AEI provide a rapid and accurate way to infer the properties of binary black hole mergers. Researchers at the AEI have used their code to analyze some of the 200 event candidates to improve accuracy and efficiency, ensuring that it meets the highest scientific standards while significantly accelerating gravitational-wave astronomy.
High precision lasers: Researchers at the AEI have provided the high-power pre-stabilized laser system for Advanced LIGO, and have developed and tested upgrades to the main laser source currently being used in the LIGO instruments. Additionally, the amplifier stage of the current laser sources in the Virgo and KAGRA instruments is based on developments and tests made by the collaboration between AEI Hannover and Laser Zentrum Hanover.
AEI researchers have developed the waveform model used to detect neutron-star–black-hole binaries and binary black holes in modeled searches that employ templates. The state-of-the-art waveform model is also employed for production runs on the signal candidates to infer their astrophysical and cosmological information.
Scientists at AEI have used signal candidates to search for deviations from general relativity. They did so by analyzing the gravitational waves emitted by the black holes and/or neutron stars well before they merge (during the “inspiral” phase of the collision).
The AEI researchers also used signal candidates to test whether the remnants of binary coalescences behave like black holes as predicted by general relativity. To do this, they analyzed the gravitational waves emitted in the final “ringdown” stage of the collision, when the resulting black hole “settles down” after the merger.
