|Despite the robust empirical supernova (SN) classification scheme in place, the underlying progenitor systems remain ambiguous for many subclasses. Direct identification of progenitor stars in pre-explosion images is typically not feasible, and astronomers are forced to rely on supernova "forensics." Here I focus on the Type IIn subclass, where the 'n' refers to a dense circumstellar medium (CSM) formed by the progenitor system. The pre-SN mass-loss history associated with this CSM is a "smoking gun,'" serving as a direct probe of the final stages of the progenitor evolution. Clues such as wind speeds, densities, compositions, and asymmetries can be used to distinguish between different progenitor systems. Unique to this talk is a focus on (1) multi-wavelength observations that probe emission originating from a range of radii, (2) late-time (> 100 days) observations that probe a range of epochs, and (3) a detailed discussion on the mysterious Type Ia-Interacting (i.e., Ia-CSM) subclass that is often confused with Type IIn.|
False-color BRI combined Keck/LRIS images of SN 2006jd on day 1609 post-detection.
The SN remains bright at optical wavelengths nearly 4.5 yr after the explosion.