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

Nicholl, M., Smartt, S. J., Jerkstrand, A., Inserra, C., McCrum, M., Kotak, R., Fraser, M., Wright, D., Chen, T.-W., Smith, K., Young, D. R., Sim, S. A., Valenti, S., Howell, D. A., Bresolin, F., Kudritzki, R. P., Tonry, J. L., Huber, M. E., Rest, A., Pastorello, A., Tomasella, L., Cappellaro, E., Benetti, S., Mattila, S., Kankare, E., Kangas, T., Leloudas, G., Sollerman, J., Taddia, F., Berger, E., Chornock, R., Narayan, G., Stubbs, C. W., Foley, R. J., Lunnan, R., Soderberg, A., Sanders, N., Milisavljevic, D., Margutti, R., Kirshner, R. P., Elias-Rosa, N., Morales-Garoffolo, A., Taubenberger, S., Botticella, M. T., Gezari, S., Urata, Y., Rodney, S., Riess, A. G., Scolnic, D., Wood-Vasey, W. M., Burgett, W. S., Chambers, K., Flewelling, H. A., Magnier, E. A., Kaiser, N., Metcalfe, N., Morgan, J., Price, P. A., Sweeney, W. and Waters, C. 2013. Slowly fading super-luminous supernovae that are not pair-instability explosions. Nature 502 (7471) , pp. 346-349. 10.1038/nature12569

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Abstract

Super-luminous supernovae1,2,3,4 that radiate more than 1044 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’ supernovae5,6. 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 56Ni are synthesized; this isotope decays to 56Fe via 56Co, powering bright light curves7,8. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe9. 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 supernova1,10. 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 supernovae2,11,12, which are not powered by radioactivity. Modelling our observations with 10–16 solar masses of magnetar-energized13,14 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Nature Research
ISSN: 0028-0836
Date of First Compliant Deposit: 2 July 2019
Date of Acceptance: 9 August 2013
Last Modified: 19 Oct 2019 06:49
URI: http://orca-mwe.cf.ac.uk/id/eprint/123932

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