Characterizing the V-band light-curves of hydrogen-rich type II
  supernovae
  We present an analysis of the diversity of V-band light-curves of
hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several
magnitude measurements are defined, together with decline rates at different
epochs, and time durations of different phases. It is found that magnitudes
measured at maximum light correlate more strongly with decline rates than those
measured at other epochs: brighter supernovae at maximum generally have faster
declining light-curves at all epochs. We find a relation between the decline
rate during the 'plateau' phase and peak magnitudes, which has a dispersion of
0.56 magnitudes, offering the prospect of using type II supernovae as purely
photometric distance indicators. Our analysis suggests that the type II
population spans a continuum from low-luminosity events which have flat
light-curves during the 'plateau' stage, through to the brightest events which
decline much faster. A large range in optically thick phase durations is
observed, implying a range in progenitor envelope masses at the epoch of
explosion. During the radioactive tails, we find many supernovae with faster
declining light-curves than expected from full trapping of radioactive
emission, implying low mass ejecta. It is suggested that the main driver of
light-curve diversity is the extent of hydrogen envelopes retained before
explosion. Finally, a new classification scheme is introduced where
hydrogen-rich events are typed as simply 'SNII' with an s2 value giving the
decline rate during the 'plateau' phase, indicating its morphological type.
