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

REGUITTI, ANDREAANDREAREGUITTIPASTORELLO, AndreaAndreaPASTORELLOPignata, G.G.PignataBENETTI, StefanoStefanoBENETTICAPPELLARO, EnricoEnricoCAPPELLAROTURATTO, MassimoMassimoTURATTOAgliozzo, C.C.AgliozzoBUFANO, FILOMENAFILOMENABUFANOMorrell, N. I.N. I.MorrellOlivares E., F.F.Olivares E.Reichart, D. E.D. E.ReichartHaislip, J. B.J. B.HaislipKouprianov, V.V.KouprianovSmartt, S. J.S. J.SmarttCiroi, S.S.Ciroi2020-12-172020-12-1720190035-8711http://hdl.handle.net/20.500.12386/28955We present photometric and spectroscopic analysis of the peculiar core-collapse supernova (SN) 2013gc, spanning 7 yr of observations. The light curve shows an early maximum followed by a fast decline and a phase of almost constant luminosity. At +200 d from maximum, a brightening of 1 mag is observed in all bands, followed by a steep linear luminosity decline after +300 d. In archival images taken between 1.5 and 2.5 yr before the explosion, a weak source is visible at the supernova location, with mag ≈20. The early supernova spectra show Balmer lines, with a narrow (∼560 km s-1) P-Cygni absorption superimposed on a broad (∼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. The complex profile of the H α line suggests a composite circumstellar medium geometry, with a combination of lower velocity, spherically symmetric gas, and a more rapidly expanding bilobed feature. This circumstellar medium distribution has been likely formed through major mass-loss events that we directly observed from 3 yr before the explosion. The modest luminosity (MI ∼ -16.5 near maximum) of SN 2013gc at all phases, the very small amount of ejected 56Ni (of the order of 10-3 M☉), the major pre-supernova stellar activity, and the lack of prominent [O I] lines in the late-time spectra support a fall-back core-collapse scenario for the massive progenitor of SN 2013gc.STAMPAenSignatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gcArticle10.1093/mnras/sty28702-s2.0-85070375982000454578700093https://academic.oup.com/mnras/article/482/2/2750/51427152019MNRAS.482.2750RFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems