SN2012ab: A peculiar Type IIn supernova with aspherical circumstellar material

Christopher Bilinski*, Nathan Smith, G. Grant Williams, Paul Smith, Weikang Zheng, Melissa L. Graham, Jon C. Mauerhan, Jennifer E. Andrews, Alexei V. Filippenko, Carl Akerlof, E. Chatzopoulos, Jennifer L. Hoffman, Leah Huk, Douglas C. Leonard, G. H. Marion, Peter Milne, Robert M. Quimby, Jeffrey M. Silverman, Jozsef Vinkó, J. Craig WheelerFang Yuan

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    21 Citations (Scopus)


    We present photometry, spectra, and spectropolarimetry of supernova (SN) 2012ab, mostly obtained over the course of ~300 d after discovery. SN 2012ab was a Type IIn (SN IIn) event discovered near the nucleus of spiral galaxy 2MASXJ12224762+0536247. While its light curve resembles that of SN 1998S, its spectral evolution does not. We see indications of CSM interaction in the strong intermediate-width emission features, the high luminosity (peak at absolute magnitude M = -19.5), and the lack of broad absorption features in the spectrum. The Hα emission undergoes a peculiar transition. At early times it shows a broad blue emission wing out to -14 000 km s-1 and a truncated red wing. Then at late times (>100 d) it shows a truncated blue wing and a very broad red emission wing out to roughly +20 000 km s-1. This late-time broad red wing probably arises in the reverse shock. Spectra also show an asymmetric intermediate-width Hα component with stronger emission on the red side at late times. The evolution of the asymmetric profiles requires a density structure in the distant CSM that is highly aspherical. Our spectropolarimetric data also suggest asphericity with a strong continuum polarization of ~1-3 per cent and depolarization in the Hα line, indicating asphericity in the CSM at a level comparable to that in other SNe IIn. We estimate a mass-loss rate of M˙ = 0.050M yr-1 for vpre = 100 km s-1 extending back at least 75 yr prior to the SN. The strong departure from axisymmetry in the CSM of SN 2012ab may suggest that the progenitor was an eccentric binary system undergoing eruptive mass loss.

    Original languageEnglish
    Article numberstx3214
    Pages (from-to)1104-1120
    Number of pages17
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number1
    Publication statusPublished - 21 Mar 2018


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