Licentiate Seminar: Observations of unusual type II supernovae

by Francesco Taddia

Wednesday 30 May 2012, 10:00 → 11:30 Europe/Stockholm

FA31

At the end of a massive star’s life when its fuel is exhausted, the core collapses under its own gravitational potential, resulting in the release of an enormous amount of energy that unbinds the star and leads to a luminous explosion known as a core-collapse supernova (CC SN). The variety of progenitor stars (> 8 M ) that give rise to CC SNe produces a large assortment of observational properties, which are reflected in the time-evolution of their spectral energy dis- tribution. Through the study of their broad-band photometry and spectroscopic evolution, we endeavour to elucidate the nature of the progenitor stars and the mass-loss history for two types of CC SN. The Carnegie Supernova Project (CSP) observed ∼100 CC SNe and its database represents a gold mine for the comprehensive study of these cosmic explosions. From the CSP sample, we consider four objects designated SNe 2005ip, 2006V, 2006au and 2006jd. Both SN 2006V and SN 2006au show striking similarity to the famous SN 1987A. This kind of CC SNe is particularly rare and, apart from SN 1987A, only our observations have complete near-IR light curves. The other two objects belong to the family of Type IIn SNe, characterized by multi- component – and in particular narrow – emission lines in their spectra. These SNe are often associated with a long-lasting optical and near-IR emission. To shed light on the the nature of these SNe, we present a comprehensive study of their observational properties. For each of these objects we provide an extensive set of optical and near-IR photometry along with optical spectroscopy, from which we draw consistent scenarios concerning the nature of their progenitor stars. We interpret the two 1987A-like SNe to result from the core-collapse of Blue Supergiants, while the two Type IIn objects are most likely SNe which exploded in a hydrogen-rich circumstellar environment.