Seminar of Theory of Relativity and Gravitation

The advanced LIGO-Virgo detectors have identified over 90 binary black hole (BBH) mergers so far, providing valuable insights into the environments where these systems form and merge. In the ongoing fourth observing run of LIGO-Virgo-KAGRA (LVK), binary black hole candidates are being detected every 3 days, owing to the increased sensitivity of the detectors. With the substantial increase in the number of BBH observations, there is growing interest in detecting gravitational waves from uncommon BBH systems, particularly those with orbital eccentricity or high masses which point to dynamical origin for these binaries. Moreover, detecting elusive intermediate-mass black hole (IMBH) mergers can have far-reaching astrophysical implications and help in understanding the formation of supermassive black holes. Template-based searches, which rely on accurate simulated waveforms can miss such events, especially in the presence of non-Gaussian noise. This highlights the importance of model-independent searches like Coherent WaveBurst (cWB) which play a crucial role in detecting gravitational waves from unusual sources like IMBH and eccentric binary black hole (eBBH) mergers. The cWB search was recently upgraded and demonstrates an improvement in the detection efficiency by approximately 40% for simulated BBH events at a false alarm rate of less than one per year. The search uncovers three candidates in LIGO-Virgo-KAGRA’s (LVK) third observing run (O3), not found by LVK’s matched-filtering searches. Notably, the most significant detection involves a black hole merger with an upper mass gap component with low mass ratio, suggesting a possible dynamical origin. Lastly, we will also discuss cWB’s sensitivity to eBBH mergers and its potential for astrophysical interpretations.