COMPARISON of DIVERSITY of TYPE IIB SUPERNOVAE with ASYMMETRY in CASSIOPEIA A USING LIGHT ECHOES

Kieran Finn, Federica B. Bianco, Maryam Modjaz, Yu Qian Liu, Armin Rest

    Research output: Contribution to journalArticle

    Abstract

    We compare the diversity of spectral line velocities in a large sample of type IIb supernovae (SNe IIb) with the expected asphericity in the explosion, as measured from the light echoes (LEs) of Cassiopeia A (Cas A), which was a historical galactic SNIIb. We revisit the results of Rest et al., who used LEs to observe CasA from multiple lines of sight and hence determine its asphericity, as seen in the velocity of three spectral lines (He i λ5876, Hα, and the Ca ii near-infrared (NIR) triplet). We confirm and improve on this measurement by reproducing the effect of the LEs in the spectra of several extragalactic SNeIIb found in the literature as well as mean SNIIb spectra recently created by Liu et al.and comparing these to the observed light echo spectra of CasA, including their associated uncertainties. In order to quantify the accuracy of this comparison,we smooth the light echo spectra of CasA using Gaussian processes and use a Monte Carlo method to measure the absorption velocities of these three features in the spectra. We then test the hypothesis that the diversity of ejecta velocities seen in SNeIIb can be explained by asphericity. We do this by comparing the range of velocities seen in the different LEs, and hence different lines of sight, of CasA to that seen in the population of SNeIIb. We conclude that these two ranges are of the same order and thus asphericity could be enough to explain the diversity in the expansion velocity alone.

    Original languageEnglish (US)
    Article number73
    JournalAstrophysical Journal
    Volume830
    Issue number2
    DOIs
    StatePublished - Oct 20 2016

    Keywords

    • ISM: supernova remnants
    • supernovae: general
    • supernovae: individual (Cas A)

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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