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We present photometric and spectroscopic analysis of the peculiarcore-collapse SN 2013gc, spanning seven years of observations. The light curveshows an early maximum followed by a fast decline and a phase of almostconstant luminosity. At +200 days from maximum, a brightening of 1 mag isobserved in all bands, followed by a steep linear luminosity decline after +300d. In archival images taken between 1.5 and 2.5 years before the explosion, aweak source is visible at the supernova location, with mag$\approx$20. Theearly supernova spectra show Balmer lines, with a narrow ($\sim$560 kms$^{-1}$) P-Cygni absorption superimposed on a broad ($\sim$3400 km s$^{-1}$)component, typical of type IIn events. Through a comparison of colour curves,absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn,we conclude that SN 2013gc is a member of the so-called type IId subgroup. Thecomplex profile of the H$\alpha$ line suggests a composite circumstellar mediumgeometry, with a combination of lower velocity, spherically symmetric gas and amore rapidly expanding bilobed feature. This circumstellar medium distributionhas been likely formed through major mass-loss events, that we directlyobserved from 3 years before the explosion. The modest luminosity($M_I\sim-16.5$ near maximum) of SN 2013gc at all phases, the very small amountof ejected $^{56}$Ni (of the order of $10^{-3}$ M$_\odot$), the majorpre-supernova stellar activity and the lack of prominent [O I] lines inlate-time spectra support a fall-back core-collapse scenario for the massiveprogenitor of SN~2013gc.

Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc