Inserra, C.C.InserraSim, S. A.S. A.SimWyrzykowski, L.L.WyrzykowskiSmartt, S. J.S. J.SmarttFraser, M.M.FraserNicholl, M.M.NichollShen, K. J.K. J.ShenJerkstrand, A.A.JerkstrandGal-Yam, A.A.Gal-YamHowell, D. A.D. A.HowellMaguire, K.K.MaguireMazzali, P.P.MazzaliValenti, S.S.ValentiTaubenberger, S.S.TaubenbergerBenitez-Herrera, S.S.Benitez-HerreraBersier, D.D.BersierBlagorodnova, N.N.BlagorodnovaCampbell, H.H.CampbellChen, T. -W.T. -W.ChenELIAS DE LA ROSA, NANCY DEL CARMENNANCY DEL CARMENELIAS DE LA ROSAHillebrandt, W.W.HillebrandtKostrzewa-Rutkowska, Z.Z.Kostrzewa-RutkowskaKozłowski, S.S.KozłowskiKromer, M.M.KromerLyman, J. D.J. D.LymanPolshaw, J.J.PolshawRöpke, F. K.F. K.RöpkeRuiter, A. J.A. J.RuiterSmith, K.K.SmithSpiro, S.S.SpiroSullivan, M.M.SullivanYaron, O.O.YaronYoung, D.D.YoungYuan, F.F.Yuan2020-04-212020-04-2120152041-8205http://hdl.handle.net/20.500.12386/24147C.I. thanks M.Kasliwal (SN2010X data). Based on observations at ESO as part of PESSTO (188.D-3003/191.D-0935/092.D-0555). Funded by FP7/2007-2013/ERC grant agreement [291222] (S.J.S.). We acknowledge support from STFC grant ST/L000709/1 (S.J.S., S.S.), TRR33 grant of DFG (S.T.), FP7/2007-2013 grant [267251] (N.E.R.), FP7/ERC grant [320360] (M.F.).We present observational data for a peculiar supernova discovered by the OGLE-IV survey and followed by the Public ESO Spectroscopic Survey for Transient Objects. The inferred redshift of z = 0.07 implies an absolute magnitude in the rest-frame I-band of M<SUB>I</SUB> ~ -17.6 mag. This places it in the luminosity range between normal Type Ia SNe and novae. Optical and near infrared spectroscopy reveal mostly Ti and Ca lines, and an unusually red color arising from strong depression of flux at rest wavelengths <5000 Å. To date, this is the only reported SN showing Ti-dominated spectra. The data are broadly consistent with existing models for the pure detonation of a helium shell around a low-mass CO white dwarf and "double-detonation" models that include a secondary detonation of a CO core following a primary detonation in an overlying helium shell.ELETTRONICOenArticle10.1088/2041-8205/799/1/L22-s2.0-84921478006000348143500002https://iopscience.iop.org/article/10.1088/2041-8205/799/1/L22015ApJ...799L...2IFIS/05 - ASTRONOMIA E ASTROFISICA