An asymptotic-giant-branch star in the progenitor system of a type Ia supernova


Stars that explode as supernovae come in two main classes. A type Ia supernova is recognized by the absence of hydrogen and the presence of elements such as silicon and sulphur in its spectrum; this class of supernova is thought to produce the majority of iron-peak elements in the Universe. They are also used as precise ‘standard candles’ to measure the distances to galaxies. While there is general agreement that a type Ia supernova is produced by an exploding white dwarf star1, no progenitor system has ever been directly observed. Significant effort has gone into searching for circumstellar material to help discriminate between the possible kinds of progenitor systems2, but no such material has hitherto been found associated with a type Ia supernova3. Here we report the presence of strong hydrogen emission associated with the type Ia supernova SN2002ic, indicating the presence of large amounts of circumstellar material. We infer from this that the progenitor system contained a massive asymptotic-giant-branch star that lost several solar masses of hydrogen-rich gas before the supernova explosion.

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Figure 1: Spectroscopic evolution of SN2002ic.
Figure 2: Decomposition and evolution of the Hα profiles.
Figure 3: Spectral analysis of SN2002ic.
Figure 4: Photometric analysis of SN2002ic.
Figure 5: Spectroscopic comparison between SN2002ic and SN1997cy.


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All the co-authors participated in gathering the observations of the supernova. M.H. noticed the presence of hydrogen emission. M.M.P. noticed spectroscopic and photometric peculiarities and put forward the idea that these could be understood as due to SN/CSM interaction. N.B.S. provided the arguments about the progenitor types. M.H., M.M.P. and N.B.S. co-wrote this Letter. M.H. is a Hubble Fellow.

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Correspondence to Mario Hamuy.

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Hamuy, M., Phillips, M., Suntzeff, N. et al. An asymptotic-giant-branch star in the progenitor system of a type Ia supernova. Nature 424, 651–654 (2003).

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