X-ray illumination of the ejecta of supernova 1987A



When a massive star explodes as a supernova, substantial amounts of radioactive elements—primarily 56Ni, 57Ni and 44Ti—are produced1. After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements2. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium3. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of 44Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.

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Figure 1: HST R-band images.
Figure 2: Light curves of the ejecta in different wavebands.
Figure 3: Evolution of the luminosity from the ejecta in the R and B bands.


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This work was supported by the Swedish Research Council and the Swedish National Space Board. Support for the HST observing programme was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc.

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J.L. carried out the data reduction and analysis together with G.Ö., P.G., B.L., J.S. and P.C.; C.F. performed the theoretical modelling together with A.J. and C.K.; and J.L. and C.F. wrote the paper. R.P.K. is the principal investigator for the HST/SAINTS collaboration. All authors discussed the results and commented on the manuscript.

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Correspondence to J. Larsson or C. Fransson.

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The authors declare no competing financial interests.

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The file contains Supplementary Text 1-4, Supplementary Figures 1-7 with legends, Supplementary Table 1 and additional references. (PDF 826 kb)

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Larsson, J., Fransson, C., Östlin, G. et al. X-ray illumination of the ejecta of supernova 1987A. Nature 474, 484–486 (2011). https://doi.org/10.1038/nature10090

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