SN 2017ens: The Metamorphosis of a Luminous Broadlined Type Ic Supernova into an SN IIn

Chen, T. -W.T. -W.ChenInserra, C.C.InserraFraser, M.M.FraserMoriya, T. J.T. J.MoriyaSchady, P.P.SchadySchweyer, T.T.SchweyerFilippenko, A. V.A. V.FilippenkoPerley, D. A.D. A.PerleyRuiter, A. J.A. J.RuiterSeitenzahl, I.I.SeitenzahlSollerman, J.J.SollermanTaddia, F.F.TaddiaAnderson, J. P.J. P.AndersonFoley, R. J.R. J.FoleyJerkstrand, A.A.JerkstrandNgeow, C. -C.C. -C.NgeowPan, Y. -C.Y. -C.PanPASTORELLO, AndreaAndreaPASTORELLOPoints, S.S.PointsSmartt, S. J.S. J.SmarttSmith, K. W.K. W.SmithTaubenberger, S.S.TaubenbergerWiseman, P.P.WisemanYoung, D. R.D. R.YoungBENETTI, StefanoStefanoBENETTIBerton, M.M.BertonBUFANO, FILOMENAFILOMENABUFANOClark, P.P.ClarkDELLA VALLE, MassimoMassimoDELLA VALLEGalbany, L.L.GalbanyGal-Yam, A.A.Gal-YamGromadzki, M.M.GromadzkiGutiérrez, C. P.C. P.GutiérrezHeinze, A.A.HeinzeKankare, E.E.KankareKilpatrick, C. D.C. D.KilpatrickKuncarayakti, H.H.KuncarayaktiLeloudas, G.G.LeloudasLin, Z. -Y.Z. -Y.LinMaguire, K.K.MaguireMazzali, P.P.MazzaliMcBrien, O.O.McBrienPrentice, S. J.S. J.PrenticeRau, A.A.RauRest, A.A.RestSiebert, M. R.M. R.SiebertStalder, B.B.StalderTonry, J. L.J. L.TonryYu, P. -C.P. -C.Yu2020-09-282020-09-2820182041-8205http://hdl.handle.net/20.500.12386/27498We present observations of supernova (SN) 2017ens, discovered by the ATLAS survey and identified as a hot blue object through the GREAT program. The redshift z = 0.1086 implies a peak brightness of M g = -21.1 mag, placing the object within the regime of superluminous supernovae. We observe a dramatic spectral evolution, from initially being blue and featureless, to later developing features similar to those of the broadlined Type Ic SN 1998bw, and finally showing ∼2000 km s-1 wide Hα and Hβ emission. Relatively narrow Balmer emission (reminiscent of a SN IIn) is present at all times. We also detect coronal lines, indicative of a dense circumstellar medium. We constrain the progenitor wind velocity to ∼50-60 km s-1 based on P-Cygni profiles, which is far slower than those present in Wolf-Rayet stars. This may suggest that the progenitor passed through a luminous blue variable phase, or that the wind is instead from a binary companion red supergiant star. At late times we see the ∼2000 km s-1 wide Hα emission persisting at high luminosity (∼3 × 1040 erg s-1) for at least 100 day, perhaps indicative of additional mass loss at high velocities that could have been ejected by a pulsational pair instability.STAMPAenSN 2017ens: The Metamorphosis of a Luminous Broadlined Type Ic Supernova into an SN IInArticle10.3847/2041-8213/aaeb2e2-s2.0-85056739355000450221300001https://iopscience.iop.org/article/10.3847/2041-8213/aaeb2e2018ApJ...867L..31CFIS/05 - ASTRONOMIA E ASTROFISICA