Journal Article

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

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

2013

Overview

Observations of two slow-to-fade super-luminous supernovae are reported; both show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Magnetar-powered super-luminous supernovae Observations of two recently discovered slow-to-fade super-luminous supernovae, known as PTF12dam and PS1-11ap, reveal relatively fast rise times and blue colours that are incompatible with the pair-instability mechanism, hitherto believed to be the best explanation for superluminous events. The authors suggest a model in which the debris from these remarkably energetic supernovae is powered by magnetic neutron stars or magnetars. Super-luminous supernovae 1 , 2 , 3 , 4 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 5 , 6 . 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 7 , 8 . Such massive progenitors are expected to have formed from metal-poor gas in the early Universe 9 . 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 1 , 10 . 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 2 , 11 , 12 , which are not powered by radioactivity. Modelling our observations with 10–16 solar masses of magnetar-energized 13 , 14 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.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/33/34/864 / Candidates / Explosions / Humanities and Social Sciences / letter / Light / Luminosity (Astronomy) / multidisciplinary / Natural history / Observations / Radioactivity / Science / Spectra / Supernovae / Supernovas