Title: Multi-messenger Collapsars

Abstract: The collapsar model suggests that when the core of a massive star exhausts its fuel, it collapses to a black hole which launches a pair of relativistic jets. Collapsars offer unique opportunities to study a wide range of cutting-edge astrophysical phenomena: heavy element nucleosynthesis, physics of relativistic jets, birth of black holes, variety of cosmic fireworks and gravitational wave sources. I will present state-of-the-art collapsar simulations that, for the first time, follow jets from a newly formed black hole to outside the star, and offer a new paradigm of wobbly jets that naturally explain quiescent times in gamma-ray bursts (GRBs). Our numerical results also suggest that newborn black holes that launch GRB jets inevitably have small spins and high kick velocities. The interaction of jets with the star leads to the formation of a hot bubble - cocoon that collimates the jets. I will show how the cocoon powers a variety of electromagnetic transients that can be detected by high cadence optical surveys. I will end with the discovery of the first class of non-inspiral gravitational wave sources, powered by collapsar cocoons, that is powerful and abundant enough such that its detection by LIGO/Virgo/KAGRA can be imminent. The gravitational waves will be accompanied by detectable bright supernova and cocoon electromagnetic emission, making jetted stellar explosions promising multi-messenger sources, enabling targeted searches for gravitational waves based on the electromagnetic counterpart detection.