title: A luminous, blue progenitor system for the type Iax supernova 2012Z.
abstract: Type Iax supernovae are stellar explosions that are spectroscopically similar to some type Ia supernovae at the time of maximum light emission, except with lower ejecta velocities. They are also distinguished by lower luminosities. At late times, their spectroscopic properties diverge from those of other supernovae, but their composition (dominated by iron-group and intermediate-mass elements) suggests a physical connection to normal type Ia supernovae. Supernovae of type Iax are not rare; they occur at a rate between 5 and 30 per cent of the normal type Ia rate. The leading models for type Iax supernovae are thermonuclear explosions of accreting carbon-oxygen white dwarfs that do not completely unbind the star, implying that they are 'less successful' versions of normal type Ia supernovae, where complete stellar disruption is observed. Here we report the detection of the luminous, blue progenitor system of the type Iax SN 2012Z in deep pre-explosion imaging. The progenitor system's luminosity, colours, environment and similarity to the progenitor of the Galactic helium nova V445 Puppis suggest that SN 2012Z was the explosion of a white dwarf accreting material from a helium-star companion. Observations over the next few years, after SN 2012Z has faded, will either confirm this hypothesis or perhaps show that this supernova was actually the explosive death of a massive star.
authors.affiliation: Department of Physics and Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
authors.forename: Curtis
authors.initials: C
authors.lastname: McCully
authors.affiliation: Department of Physics and Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
authors.forename: Saurabh W
authors.initials: SW
authors.lastname: Jha
authors.affiliation: 1] Astronomy Department, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801, USA [2] Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Foley
authors.affiliation: 1] Department of Physics, University of California, Santa Barbara, California 93106, USA [2] Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Lars
authors.initials: L
authors.lastname: Bildsten
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Wen-fai
authors.initials: WF
authors.lastname: Fong
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Kirshner
authors.affiliation: 1] Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA [2] Department of Astronomy, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: G H
authors.initials: GH
authors.lastname: Marion
authors.affiliation: 1] Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA [2] Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA.
authors.forename: Adam G
authors.initials: AG
authors.lastname: Riess
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
authors.forename: Maximilian D
authors.initials: MD
authors.lastname: Stritzinger
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references.pmid: 19494909
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references.pmid: 22170681