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Discovery of the progenitor of the type Ia supernova 2007on


Type Ia supernovae are exploding stars that are used to measure the accelerated expansion of the Universe1,2 and are responsible for most of the iron ever produced3. Although there is general agreement that the exploding star is a white dwarf in a binary system, the exact configuration and trigger of the explosion is unclear4, which could hamper their use for precision cosmology. Two families of progenitor models have been proposed. In the first, a white dwarf accretes material from a companion until it exceeds the Chandrasekhar mass, collapses and explodes5,6. Alternatively, two white dwarfs merge, again causing catastrophic collapse and an explosion7,8. It has hitherto been impossible to determine if either model is correct. Here we report the discovery of an object in pre-supernova archival X-ray images at the position of the recent type Ia supernova (2007on) in the elliptical galaxy NGC 1404. Deep optical images (also archival) show no sign of this object. From this we conclude that the X-ray source is the progenitor of the supernova, which favours the accretion model for this supernova, although the host galaxy is older (6–9 Gyr) than the age at which the explosions are predicted in the accreting models.

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Figure 1: Images of the region around SN2007on.


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We thank the Central Bureau for Astronomical Telegrams for providing a list of supernovae. This research has made use of data obtained from the Chandra Data Archive and software provided by the Chandra X-ray Center in the application package CIAO, and of Swift data obtained from the High Energy Astrophysics Science Archive Research Center, provided by NASA’s Goddard Space Flight Center. The observations from the NASA/ESA Hubble Space Telescope were obtained from the data archive at the Space Telescope Institute. We thank NOVA for support. G.N. is supported by an NWO VENI grant.

Author Contributions The authors have contributed equally to the paper.

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Correspondence to Rasmus Voss or Gijs Nelemans.

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Voss, R., Nelemans, G. Discovery of the progenitor of the type Ia supernova 2007on. Nature 451, 802–804 (2008).

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