Date of Award
Doctor of Philosophy (PhD)
In this golden era of multi-messenger astronomy, with highly sensitive telescopes detecting spectacular transients almost nightly, a whole new window is now wide open to study the universe on all timescales. Typically, these events are generated from the total or partial destruction of an astrophysical object and emit electromagnetic waves of all different wavelengths, neutrinos and gravitational waves--carrying important physics that was previously inaccessible. Therefore, it is of utmost importance to take advantage of this tremendous progress in observation with analytic and simulation tools to explain the physics of exotic astrophysical events. This thesis aims to do so by studying the hydrodynamics of some of the most exotic high-energy astrophysical phenomena, ranging from tidal disruption events, shock physics, accretion, and gravitational wave emission from core collapse supernovae, and dynamic stability of the giant planetary atmosphere. We have developed novel analytical tools, primarily using classical hydrodynamics and general relativity, and have utilized computational techniques (numerical and simulations). Our study on giant planets shows how the presence of a solid core can save the planet from being unstable when due to ionization it is expected to be, and thus solves a puzzle in the ``core-accretion” theory of giant planet formation. We have presented a general relativistic modification for the accretion solution on a neutron star through stalled shock, which is useful in understanding weak or failed supernovae and can potentially impact the much-discussed standing accretion shock instability--which we restudied and in the process uncovered a new variant impacting the explosion mechanism and gravitational-wave signature. We have also studied the oscillation modes of a nascent proto-neutron star to show how they can contribute to the gravitational wave signature emitted. Our study of deep-tidal disruption events (events in which stars approach black holes closely) refutes the widely speculated possibility of nuclear detonation arising in such events.
Kundu, Suman Kumar, "Hydrodynamics, Stability and Accretion: from planets, to stars, to supermassive black holes" (2023). Dissertations - ALL. 1770.