Investigating the Expansion Velocities of Type II-P Supernovae

Type II-P supernovae (SNe) are the most frequently observed of the known core collapse (CC) supernovae varieties, making up ~60% of all CC SNe. Type II-P CC scenarios occur from progenitor stars with initial masses greater than ~8 solar masses, showing strong hydrogen features in the optical spectra. These SNe derive their “plateau” sobriquet from their ~100 day plateau of nearly constant optical brightness. The progenitors of a SNe II-P have been convincingly shown to be red supergiants (Smartt 2009, ARAA, 47, 63).

The expansion velocity of SN II-P ejecta has been shown to be a key measurement to make about the explosion, as it correlates with many other important parameters such as explosion energy and luminosity. The most well accepted way of measuring velocity is through the measurement of the blue shifted absorption feature of Fe II at 516.9 nm. Here I will present preliminary results of expansion velocity measurements from a sample of recent SNe II-P drawn largely from the WISEREP spectral database. Objects that show unusual temporal trends will be highlighted.