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An absence of ex-companion stars in the type Ia supernova remnant SNR 0509−67.5



A type Ia supernova is thought to begin with the explosion of a white dwarf star1. The explosion could be triggered by the merger of two white dwarfs2,3 (a ‘double-degenerate’ origin), or by mass transfer from a companion star4,5 (the ‘single-degenerate’ path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin6 has been widely rejected7,8,9,10,11. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present12,13. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified14, but that claim is still controversial15,16,17,18. Here we report that the central region of the supernova remnant SNR 0509−67.5 (the site of a type Ia supernova 400 ± 50 years ago, based on its light echo19,20) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of MV = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been ‘kicked’ by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.

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Figure 1: SNR 0509−67.5 and the extreme 99.73% error circle.


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The HST images were taken as part of two programmes with Principal Investigators J. P. Hughes and K. Noll. This work was supported by the National Science Foundation.

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The authors shared the ideas, the data analysis, and the writing of this paper.

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Correspondence to Bradley E. Schaefer.

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The authors declare no competing financial interests.

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HST images comprising Fig. 1 are in the public domain (,

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Schaefer, B., Pagnotta, A. An absence of ex-companion stars in the type Ia supernova remnant SNR 0509−67.5. Nature 481, 164–166 (2012).

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