Type Ia supernovae are destructive explosions of carbon-oxygen white dwarfs. Although they are used empirically to measure cosmological distances, the nature of their progenitors remains mysterious. One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion. Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star, and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel.
Bibliographical noteFunding Information:
Carnegie-Princeton fellowship. Supernova research at the Oskar Klein Centre is supported by the Swedish Research Council and by the Knut and Alice Wallenberg Foundation. The National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under contract number DE-AC02-05CH11231, provided staff, computational resources, and data storage for this project. The participation of the Los Alamos National Laboratory (LANL) in iPTF is supported by the US Department of Energy as part of the Laboratory Directed Research and Development programme. A portion of this work was carried out at the Jet Propulsion Laboratory under a Research and Technology Development Grant, under contract with the National Aeronautics and Space Administration.
Acknowledgements We thank A. L. Piro, M. Kromer and J. Cohen for discussions. We also thank A. Waszczak, A. Rubin, O. Yaron, A. De Cia, D. A. Perley, G. E. Duggan, O. Smirnova, S. Papadogiannakis, A. Nyholm, Y. F. Martinez and the staff at the Nordic Optical Telescope and Gemini for observation and data reduction. Some of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA. The observatory was made possible by the generous financial supportofthe W.M.KeckFoundation.Some datawereobtainedwiththe Nordic Optical Telescope, which is operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain. This work also makes use of observations from the Las Cumbres Observatory Global Telescope (LCOGT) network. Research at California Institute of Technology is supported by the National Science Foundation. D.A.H. acknowledges support from the National Science Foundation. A.G.-Y. acknowledges support from the EU/FP7 via an ERC grant, the ‘‘Quantum Universe’’ I-Core programme, the ISF, Minerva and Weizmann-UK grants, and the Kimmel Award. M.M.K. acknowledges generous support from the
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