title: An asymptotic-giant-branch star in the progenitor system of a type Ia supernova.
abstract: 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 star, 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 systems, but no such material has hitherto been found associated with a type Ia supernova. 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.
authors.affiliation: Carnegie Observatories, 813 Santa Barbara Street, Pasadena, California 91101, USA. mhamuy@ociw.edu
authors.forename: Mario
authors.initials: M
authors.lastname: Hamuy
authors.forename: M M
authors.initials: MM
authors.lastname: Phillips
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Suntzeff
authors.forename: José
authors.initials: J
authors.lastname: Maza
authors.forename: L E
authors.initials: LE
authors.lastname: González
authors.forename: Miguel
authors.initials: M
authors.lastname: Roth
authors.forename: Kevin
authors.initials: K
authors.lastname: Krisciunas
authors.forename: Nidia
authors.initials: N
authors.lastname: Morrell
authors.forename: E M
authors.initials: EM
authors.lastname: Green
authors.forename: S E
authors.initials: SE
authors.lastname: Persson
authors.forename: P J
authors.initials: PJ
authors.lastname: McCarthy
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D019418:Evolution, Chemical; D005118:Extraterrestrial Environment / Q000737:chemistry*; D005740:Gases / Q000032:analysis; D006859:Hydrogen / Q000032:analysis*
chemical_list: D005740:Gases; D006859:Hydrogen