Slowly fading super-luminous supernovae that are not pair-instability explosions

M. Nicholl*, S. J. Smartt, A. Jerkstrand, C. Inserra, M. McCrum, R. Kotak, M. Fraser, D. Wright, T. W. Chen, K. Smith, D. R. Young, S. A. Sim, S. Valenti, D. A. Howell, F. Bresolin, R. P. Kudritzki, J. L. Tonry, M. E. Huber, A. Rest, A. PastorelloL. Tomasella, E. Cappellaro, S. Benetti, S. Mattila, E. Kankare, T. Kangas, G. Leloudas, J. Sollerman, F. Taddia, E. Berger, R. Chornock, G. Narayan, C. W. Stubbs, R. J. Foley, R. Lunnan, A. Soderberg, N. Sanders, D. Milisavljevic, R. Margutti, R. P. Kirshner, N. Elias-Rosa, A. Morales-Garoffolo, S. Taubenberger, M. T. Botticella, S. Gezari, Y. Urata, S. Rodney, A. G. Riess, D. Scolnic, W. M. Wood-Vasey, W. S. Burgett, K. Chambers, H. A. Flewelling, E. A. Magnier, N. Kaiser, N. Metcalfe, J. Morgan, P. A. Price, W. Sweeney, C. Waters

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

172 Scopus citations

Abstract

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 65-130 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 56 Ni are synthesized; this isotope decays to 56 Fe via 56 Co, 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 6 × 10 -6 times that of the core-collapse rate.

Original languageEnglish (US)
Pages (from-to)346-349
Number of pages4
JournalNature
Volume502
Issue number7471
DOIs
StatePublished - 2013

ASJC Scopus subject areas

  • General

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