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This article reviews the developments on the topic of so-called changing-look active galactic nuclei from the past ten years or so. These active galactic nuclei show dramatic flux and spectral changes at X-ray, ultraviolet and optical wavelengths, due to either obscuration or changes in accretion rate.
Continuous gravitational waves represent an exciting new frontier for multi-messenger astrophysics. This overview discusses their origins and the results obtained in the LIGO–Virgo–KAGRA O3 observing run, highlighting their potential for future studies.
