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Hydrogen-poor superluminous stellar explosions



Supernovae are stellar explosions driven by gravitational or thermonuclear energy that is observed as electromagnetic radiation emitted over weeks or more1. In all known supernovae, this radiation comes from internal energy deposited in the outflowing ejecta by one or more of the following processes: radioactive decay of freshly synthesized elements2 (typically 56Ni), the explosion shock in the envelope of a supergiant star3, and interaction between the debris and slowly moving, hydrogen-rich circumstellar material4. Here we report observations of a class of luminous supernovae whose properties cannot be explained by any of these processes. The class includes four new supernovae that we have discovered and two previously unexplained events5,6 (SN 2005ap and SCP 06F6) that we can now identify as members of the same class. These supernovae are all about ten times brighter than most type Ia supernova, do not show any trace of hydrogen, emit significant ultraviolet flux for extended periods of time and have late-time decay rates that are inconsistent with radioactivity. Our data require that the observed radiation be emitted by hydrogen-free material distributed over a large radius (1015 centimetres) and expanding at high speeds (>104 kilometres per second). These long-lived, ultraviolet-luminous events can be observed out to redshifts z > 4.

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Figure 1: Ultraviolet-luminous transients discovered by the PTF.
Figure 2: Spectral energy distributions of the SN 2005ap-like sample.
Figure 3: Luminosity evolution of the SN 2005ap-like sample.


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Observations were obtained with the Samuel Oschin Telescope and the 60-inch telescope at Palomar Observatory as part of the PTF project, a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford and the Weizmann Institute of Science. Some of the data presented here were obtained at the W. M. Keck Observatory and the William Herschel Telescope. The National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy, provided staff, computational resources and data storage for this project. Observations by the Weizmann PTF partnership and from the Wise Observatory are supported by grants from the Israel Science Foundation and the US–Israel Binational Science Foundation. We acknowledge support from the US Department of Energy Scientific Discovery through Advanced Computing programme, the Hale Fellowship from the Gordon and Betty Moore foundation, the Bengier Foundation, the Richard and Rhoda Goldman Fund, and the Royal Society.

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Authors and Affiliations



R.M.Q. initiated, coordinated and managed the project, carried out photometric and spectroscopic observations and analysis, and wrote the manuscript. S.R.K. is the PTF principal investigator and contributed to manuscript preparation. M.M.K. obtained spectroscopy from the Keck I telescope and helped with the P60 observations. A.G.-Y. oversaw the Wise observations and contributed to analysis and manuscript writing. I.A. extracted the Wise photometry and helped obtain Keck I spectra. M.S. carried out and analysed spectroscopic observations from the William Herschel Telescope. P.N. designed and implemented the image-subtraction pipeline that detected the PTF events. R.T. analysed the combined spectra using his automated SYNOW code. D.A.H. helped to identify the PTF spectra as being like that of SN 2005ap. E.N. contributed to the physical interpretation and manuscript writing. L.B. advised during the preparation of the manuscript. C.T. helped vet potential candidates and first identified PTF09atu and PTF09cwl. N.M.L. is the PTF project scientist and oversaw the PTF system. R.D., G.R., D.H., R.S., E.O.O., J.Z., V.V., R.W., J.H., K.B. and D.M. helped to build and commission the PTF system. D.P., S.B.C. and D.L. helped to vet PTF candidates and obtain spectroscopic observations.

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Correspondence to R. M. Quimby.

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The authors declare no competing financial interests.

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Quimby, R., Kulkarni, S., Kasliwal, M. et al. Hydrogen-poor superluminous stellar explosions. Nature 474, 487–489 (2011).

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