The peculiar Type Ia supernova iPTF14atg: Chandrasekhar-mass explosion or violent merger?

M. Kromer*, C. Fremling, R. Pakmor, S. Taubenberger, R. Amanullah, S. B. Cenko, C. Fransson, A. Goobar, G. Leloudas, F. Taddia, F. K. Röpke, I. R. Seitenzahl, S. A. Sim, J. Sollerman

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    63 Citations (Scopus)

    Abstract

    iPTF14atg, a subluminous peculiar Type Ia supernova (SN Ia) similar to SN 2002es, is the first SN Ia for which a strong UV flash was observed in the early-time light curves. This has been interpreted as evidence for a single-degenerate (SD) progenitor system, where such a signal is expected from interactions between the SN ejecta and the non-degenerate companion star. Here, we compare synthetic observables of multidimensional state-of-the-art explosion models for different progenitor scenarios to the light curves and spectra of iPTF14atg. From our models, we have difficulties explaining the spectral evolution of iPTF14atg within the SD progenitor channel. In contrast, we find that a violent merger of two carbon-oxygen white dwarfs with 0.9 and 0.76 M, respectively, provides an excellent match to the spectral evolution of iPTF14atg from 10 d before to several weeks after maximum light. Our merger model does not naturally explain the initial UV flash of iPTF14atg. We discuss several possibilities like interactions of the SN ejecta with the circumstellar medium and surface radioactivity from an He-ignited merger that may be able to account for the early UV emission in violent merger models.

    Original languageEnglish
    Pages (from-to)4428-4439
    Number of pages12
    JournalMonthly Notices of the Royal Astronomical Society
    Volume459
    Issue number4
    DOIs
    Publication statusPublished - 11 Jul 2016

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