DES16C3cje: A low-luminosity, long-lived supernova

Author(s): Gutierrez, CP; Sullivan, M; Martinez, L; Bersten, MC; Inserra, C; Smith, M; Anderson, JP; Pan, Y-C; Pastorello, A; Galbany, L; Nugent, P; Angus, CR; Barbarino, C; Chen, T-W; Davis, TM; Valle, M Della; Foley, RJ; Fraser, M; Frohmaier, C; Gonzalez-Gaitan, S; Lewis, GF; Gromadzki, M; Kankare, E; Kokotanekova, R; Kollmeier, J; Magee, MR; Maguire, K; Moller, A; Morrell, N; Nicholl, M; Pursiainen, M; Sollerman, J; Sommer, NE; Swann, E; Tucker, BE; Wiseman, P; Aguena, M; Allam, S; Avila, S; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, DL; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Costanzi, M; Costa, LN da; Vicente, J De; Desai, S; Diehl, HT; Doel, P; Eifler, TF; Flaugher, B; Fosalba, P; Frieman, J; Garcia-Bellido, J; Gerdes, DW; Gruen, D; Gruendl, RA; Gschwend, J; Gutierrez, G; Hinton, SR; Hollowood, DL; Honscheid, K; James, DJ; Kuehn, K; Kuropatkin, N; Lahav, O; Lima, M; Maia, MAG; March, M; Menanteau, F; Miquel, R; Morganson, E; Palmese, A; Paz-Chinchon, F; Plazas, AA; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Serrano, S; Sevilla-Noarbe, I; Soares-Santos, M | Abstract: We present DES16C3cje, a low-luminosity, long-lived type II supernova (SN II) at redshift 0.0618, detected by the Dark Energy Survey (DES). DES16C3cje is a unique SN. The spectra are characterized by extremely narrow photospheric lines corresponding to very low expansion velocities of $\lesssim1500$ km s$^{-1}$, and the light curve shows an initial peak that fades after 50 days before slowly rebrightening over a further 100 days to reach an absolute brightness of M$_r\sim -15.5$ mag. The decline rate of the late-time light curve is then slower than that expected from the powering by radioactive decay of $^{56}$Co but is comparable to that expected from accretion power. Comparing the bolometric light curve with hydrodynamical models, we find that DES16C3cje can be explained by either i) a low explosion energy (0.11 foe) and relatively large $^{56}$Ni production of 0.075 M$_{\odot}$ from a $\sim15$ M$_{\odot}$ red supergiant progenitor typical of other SNe II, or ii) a relatively compact $\sim40$ M$_{\odot}$ star, explosion energy of 1 foe, and 0.08 M$_{\odot}$ of $^{56}$Ni. Both scenarios require additional energy input to explain the late-time light curve, which is consistent with fallback accretion at a rate of $\sim0.5\times{10^{-8}}$ M$_{\odot}$ s$^{-1}$.