| Abstract: | Mass loss during the evolutionary lifetime of stars plays a crucial role in determining their final stages, but the true rate of mass loss, and the evolutionary stage at which it occurs, remains largely unknown, especially in the case of massive, low metallicity stars. Supernovae with massive (M>10 M_sun) progenitors reveal the existence of a circumstellar medium (CSM), the nature and morphology of which appears to depend on the progenitor properties, as well as on the properties of the star-forming region associated with the progenitor. We present here optical studies of several type-IIn supernovae, (with focus on SN2023usc) at epochs ranging from early cooling to late nebular stage, and explore the inferred variations in the CSM's physical properties and geometry. We find that an asymmetric distribution of CSM, either via a disk, bipolar or even a multi-shelled morphology, greatly influences the spectral line profiles, especially early in the event's temporal evolution. We find that the class of interacting supernovae with dense CSM (type-IIn) consists of at least two sub-types -- the long lived, super luminous type-IIn events like SN2017hcc, which remain intrinsically bright for up to several years, and the short lived ones (e.g. SN2023usc) which reach nebular stage within a few $\times$ 100 d. This suggests that there may be multiple factors, including progenitor mass, metallicity, and even binarity which may be responsible for optical properties of this relatively rare class of supernovae.
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