Terreran, G.G.TerreranJerkstrand, A.A.JerkstrandBENETTI, StefanoStefanoBENETTISmartt, S. J.S. J.SmarttOchner, P.P.OchnerTOMASELLA, LinaLinaTOMASELLAHowell, D. A.D. A.HowellMorales-Garoffolo, A.A.Morales-GaroffoloHarutyunyan, A.A.HarutyunyanKankare, E.E.KankareArcavi, I.I.ArcaviCAPPELLARO, EnricoEnricoCAPPELLAROELIAS DE LA ROSA, NANCY DEL CARMENNANCY DEL CARMENELIAS DE LA ROSAHosseinzadeh, G.G.HosseinzadehKangas, T.T.KangasPASTORELLO, AndreaAndreaPASTORELLOTartaglia, L.L.TartagliaTURATTO, MassimoMassimoTURATTOValenti, S.S.ValentiWiggins, P.P.WigginsYuan, F.F.Yuan2020-05-222020-05-2220160035-8711http://hdl.handle.net/20.500.12386/25078We present multiband ultraviolet, optical, and near-infrared photometry, along with visual-wavelength spectroscopy, of supernova (SN) 2014G in the nearby galaxy NGC 3448 (25 Mpc). The early-phase spectra show strong emission lines of the high ionization species He II/N IV/C IV during the first 2-3 d after explosion, traces of a metal-rich circumstellar material (CSM) probably due to pre-explosion mass-loss events. These disappear by day 9 and the spectral evolution then continues matching that of normal Type II SNe. The post-maximum light curve declines at a rate typical of Type II-L class. The extensive photometric coverage tracks the drop from the photospheric stage and constrains the radioactive tail, with a steeper decline rate than that expected from the <SUP>56</SUP>Co decay if γ-rays are fully trapped by the ejecta. We report the appearance of an unusual feature on the blue side of H α after 100 d, which evolves to appear as a flat spectral feature linking H α and the [O I] doublet. This may be due to interaction of the ejecta with a strongly asymmetric, and possibly bipolar CSM. Finally, we report two deep spectra at ∼190 and 340 d after explosion, the latter being arguably one of the latest spectra for a Type II-L SN. By modelling the spectral region around the [Ca II], we find a supersolar Ni/Fe production. The strength of the [O I] λλ6300,6363 doublet, compared with synthetic nebular spectra, suggests a progenitor with a zero-age main-sequence mass between 15 and 19 M<SUB>☉</SUB>.STAMPAenArticle10.1093/mnras/stw15912-s2.0-84988693377000383516700035https://academic.oup.com/mnras/article/462/1/137/25894602016MNRAS.462..137TFIS/05 - ASTRONOMIA E ASTROFISICA