Interpreting UV/Optical Type IIn Supernova Light Curves Using a Simple Modeling Approach

Core-collapse supernovae enrich the universe with the heavy elements necessary for stellar, galaxy and planetary formation. This thesis focuses on unraveling the physical process which drive the release of energy and stellar material as the core of a massive star collapses by using a simple modeling technique to replicate early ultraviolet and optical supernova emissions. This work focuses on using early mid-ultraviolet and optical observations of Type IIn supernovae observed by Swift Ultraviolet-Optical Telescope (UVOT), to understand the behavior of supernova explosions. Understanding the UV characteristics of nearby IIn supernovae during an early phase can provide valuable information about the environment surrounding these explosions, leading us to evaluating the diversity of observational properties in this subclass. We use a simple semi-analytical SN model in order to understand the effects of the explosion environment on IIn UV observations. These simplified SN models can be processed quickly in order to explore the properties of the progenitor star along with explosion mechanism and circumstellar medium. We are able to rapidly explore the diversity of the SN light curves by studying the effects of various explosion and progenitor star parameters including, ejecta mass, explosion energy, stellar radii, shock temperature and velocity using this 'simple' calculation technique. Furthermore, we compare UV and optical modeled light-curves to Swift UVOT IIn observations to identify the general initial conditions which enable the difference between SN 2009ip and SN 2011ht light-curve properties. Our results indicate that the peak light-curve is dominated by the shock temperature, and explosion energy, whereas the shape depends on the mass of the ejecta, and the explosion energy. Based on this modeling approach, the comparison SN light curves are a product of processes occurring after shock breakout, but before nickel-56 decay. In general, the diversity between SN 2009ip and SN 2011ht can be explained by the differences in the outer ejecta mass, and the explosion energy. By including the effects of shock velocities during shock breakout, we deduce the rapid rise and decay of IIn UV light curves is the product of higher shock breakout velocity which depends on the explosion energy and the density of the outermost SN ejecta shell.