Hunting for elusive multi-messenger transients with INTEGRAL

Recent years were marked by breakthrough observations of new multi-messenger and multiwavelength transients, often unveiling unanticipated and puzzling phenomena. Likely associated with most energetic processes in the dense region at the heart of peculiar supernovae, mergers of compact objects, or tidal disruption events, these events expose unique signatures in hard X-ray and gamma-ray emission. I highlight recent pioneering observations of short energetic transients made with INTEGRAL, which is especially well-equipped to observe unpredictable, short-lived, and energetic hard X-ray and gamma-ray transients. It carries a collection of detectors that monitor the entire hard X-ray sky with over 80% duty cycle and is able to re-point to perform deep and sensitive hard X-ray observations of any large selected sky region. I discuss the observations of gamma-ray bursts, in particular in association with the gravitational wave events and high-energy neutrinos, and review how INTEGRAL observations of fast hard X-ray transients help to reveal mechanisms of the peculiar supernovae. Finally, I will discuss how the recent discoveries in the domain of multimessenger transients were made possible by a global effort to achieve a new degree of automation and interoperability.