Search for Microlensing Signature in Gravitational Waves from Binary Black Hole Events

Kyungmin Kim

Submitted on 30 October 2022


In a recent search (Kim et al. 2022), we looked for microlensing signature in gravitational waves from spectrograms of the binary black hole events in the first and second gravitational-wave transient catalogs. For the search, we have implemented a deep learning-based method (Kim et al. 2021) and figured out that one event, GW190707 093326, out of forty-six events, is classified into the lensed class. However, upon estimating the p-value of this event, we observed that the uncertainty of the p-value still includes the possibility of the event being unlensed. Therefore, we concluded that no significant evidence of beating patterns from the evaluated binary black hole events has found from the search. For a consequence study, we discuss the distinguishability between microlensed gravitational waves and the signal from precessing black hole binaries.


Comment: 2 pages, 1 figure, submitted for the proceeding of the IAU Symposium 368: Machine Learning in Astronomy

Subjects: Astrophysics - Instrumentation and Methods for Astrophysics; Astrophysics - High Energy Astrophysical Phenomena; General Relativity and Quantum Cosmology


Example waveforms showing how different a microlensed GW signal against the signal of a precessing BBH merger. We assume the same component mass ($m_1=m_2=30M_\odot$) and the same distance to the source ($500\textrm{Mpc}$) for both cases. For the generation of the signal from precessing BBH merger, we set arbitrary spin vectors for each component black hole. For microlensed signals, we adopt the point-mass lens model in the geometrical optics limit with the source position parameter $y=0.3$ and the redshifted lens mass $M_{lz}=10^4M_\odot$. (see \cite{takahashi:2003apj} for details of lensing configuration and formulation.)