|M.Sc Student||Mcley Liron|
|Subject||Stellar Instability and Intermediate Luminosity Optical|
|Department||Department of Physics||Supervisor||Professor Noam Soker|
|Full Thesis text|
It is only in the last decade or so that we have started to observe transient events that are brighter than the typical novae, and at the same time dimmer than the typical supernovae. These events represent a heterogeneous new group of phenomenon and they are denoted as Intermediate Luminosity Optical Transients (ILOTs; Red Transients; Red Novae). The mechanism powering these transients is still open for vigorous debate, with some saying that it is part of the evolution process of a single star while others attributing it to binary interactions. My work is divided into two main chapters, each dealing with a different single-star model. In the first chapter I discuss an ILOT mechanism which suggests that a shock wave, powered by an intense energy release from the core of asymptotic giant branch (AGB) stars, can eject a small portion of the envelope at very high velocities. I find that this scenario is very unlikely and that instead the shock wave that is required to explain the observed mass loss also ejects most of the envelope. The second chapter deals with a model which suggests that core convection generates waves that can drive episodic mass loss from the envelope of massive stars before they become supernovae. I argue that such energy leakage from the core is far more likely to cause envelope expansion as the waves should greatly contribute to the overall pressure in the envelope.