Dong, SuboSuboDongKatz, BoazBoazKatzKollmeier, Juna A.Juna A.KollmeierKushnir, DoronDoronKushnirELIAS DE LA ROSA, NANCY DEL CARMENNANCY DEL CARMENELIAS DE LA ROSABose, SubhashSubhashBoseMorrell, NidiaNidiaMorrellPrieto, J. L.J. L.PrietoChen, PingPingChenKochanek, C. S.C. S.KochanekBrandt, G. M.G. M.BrandtHoloien, T. W. -S.T. W. -S.HoloienGal-Yam, AvishayAvishayGal-YamMorales-Garoffolo, AntoniaAntoniaMorales-GaroffoloParker, StuartStuartParkerPhillips, M. M.M. M.PhillipsPiro, Anthony L.Anthony L.PiroShappee, B. J.B. J.ShappeeSimon, Joshua D.Joshua D.SimonStanek, K. Z.K. Z.Stanek2020-10-222020-10-2220180035-8711http://hdl.handle.net/20.500.12386/27935We present nebular-phase spectra of the Type Ia supernova (SN Ia) 2016brx, a member of the 1991bg-like subclass that lies at the faint end of the SN Ia luminosity function. Nebular spectra are available for only three other 1991bg-like SNe, and their Co line centres are all within ≲500 km s-1 of each other. In contrast, the nebular Co line centre of SN 2016brx is blue-shifted by >1500 km s-1 compared to them and by ≈1200 km s-1 compared to the rest frame. This is a significant shift relative to the narrow nebular line velocity dispersion of ≲2000 km s-1 of these SNe. The large range of nebular line shifts implies that the 56Ni in the ejecta of SN 1991bg-like events is off-centre by ∼1000 km s-1 rather than universally centrally confined as previously suggested. With the addition of SN 2016brx, the Co nebular line shapes of 1991bg-like objects appear to connect with the brighter SNe Ia that show double-peaked profiles, hinting at a continuous distribution of line profiles among SNe Ia. One class of models to produce both off-centre and bimodal 56Ni distributions is collisions of white dwarfs with unequal and equal masses.STAMPAenArticle10.1093/mnrasl/sly0982-s2.0-85054742643000446987300014https://arxiv.org/pdf/1805.00010.pdfhttps://academic.oup.com/mnrasl/article/479/1/L70/50323822018MNRAS.479L..70DFIS/05 - ASTRONOMIA E ASTROFISICA