Slowly fading super-luminous supernovae that are not pair-instability explosions
Creators: name: Nicholl, M.
name: Smartt, S. J.
name: Jerkstrand, A.
name: Inserra, C.
name: McCrum, M.
name: Kotak, R.
name: Fraser, M.
name: Wright, D.
name: Chen, T. -W.
name: Smith, K.
name: Young, D. R.
name: Sim, S. A.
name: Valenti, S.
name: Howell, D. A.
name: Bresolin, F.
name: Kudritzki, R. P.
name: Tonry, J. L.
name: Huber, M. E.
name: Rest, A.
name: Pastorello, A.
name: Tomasella, L.
name: Cappellaro, E.
name: Benetti, S.
name: Mattila, S.
name: Kankare, E.
name: Kangas, T.
name: Leloudas, G.
name: Sollerman, J.
name: Taddia, F.
name: Berger, E.
name: Chornock, R.
name: Narayan, G.
name: Stubbs, C. W.
name: Foley, R. J.
name: Lunnan, R.
name: Soderberg, A.
name: Sanders, N.
name: Milisavljevic, D.
name: Margutti, R.
name: Kirshner, R. P.
name: Elias-Rosa, N.
name: Morales-Garoffolo, A.
name: Taubenberger, S.
name: Botticella, M. T.
name: Gezari, S.
name: Urata, Y.
name: Rodney, S.
name: Riess, A. G.
name: Scolnic, D.
name: Wood-Vasey, W. M.
name: Burgett, W. S.
name: Chambers, K.
name: Flewelling, H. A.
name: Magnier, E. A.
name: Kaiser, N.
name: Metcalfe, N.
name: Morgan, J.
name: Price, P. A.
name: Sweeney, W.
name: Waters, C.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Super-luminous supernovae that radiate more than 10^44 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-30 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of 56Ni are synthesized; this isotope decays to 56Fe via 56Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6x10^-6 times that of the core-collapse rate.
description: Originally published in Nature, Oct 2013. Updated Oct 2016 to correct an error