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Type IIn Supernovae (SNe IIn) are rare events, constituting only a fewpercent of all core-collapse SNe, and the current sample of well observed SNeIIn is small. Here, we study the four SNe IIn observed by the CaltechCore-Collapse Project (CCCP). The CCCP SN sample is unbiased to the extent thatobject selection was not influenced by target SN properties. Therefore, theseevents are representative of the observed population of SNe IIn. We find that anarrow P-Cygni profile in the hydrogen Balmer lines appears to be a ubiquitousfeature of SNe IIn. Our light curves show a relatively long rise time (>20days) followed by a slow decline stage (0.01 to 0.15 mag/day), and a typicalV-band peak magnitude of M_V=-18.4 +/- 1.0 mag. We measure the progenitor starwind velocities (600 - 1400 km/s) for the SNe in our sample and derivepre-explosion mass loss rates (0.026 - 0.12 solar masses per year). We compilesimilar data for SNe IIn from the literature, and discuss our results in thecontext of this larger sample. Our results indicate that typical SNe IIn arisefrom progenitor stars that undergo LBV-like mass-loss shortly before theyexplode.

Caltech Core-Collapse Project (CCCP) observations of type IIn supernovae: typical properties and implications for their progenitor stars