SN 2011hw: Helium-rich circumstellar gas and the luminous blue variable to Wolf-Rayet transition in supernova progenitors

Nathan Smith, Jon C. Mauerhan, Jeffrey M. Silverman, Mohan Ganeshalingam, Alexei V. Filippenko, S. Bradley Cenko, Kelsey I. Clubb, Michael T. Kandrashoff

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

We present optical photometry and spectroscopy of the peculiar Type IIn/Ibn supernova (SN) 2011hw. Its optical light curve exhibits a slower decline rate than that of normal SNe Ibc, with a peak absolute magnitude of -19.5 (unfiltered) and a secondary rise 20-30 d later of -18.3mag (R). Spectra of SN 2011hw are highly unusual compared to those of normal SN types, most closely resembling the spectra of SNe Ibn. We centre our analysis on comparing SN 2011hw to the well-studied Type Ibn SN 2006jc. While the two SNe have many important similarities, the differences are quite telling: compared to SN 2006jc, SN 2011hw has weaker He I and Ca II lines and relatively stronger H lines, its light curve exhibits a higher visual-wavelength luminosity and slower decline rate, and emission lines associated with the progenitor's circumstellar material (CSM) are narrower. One can reproduce the unusual continuum shape of SN 2011hw with roughly equal contributions from a 6000-K blackbody and a spectrum of SN 2006jc. We attribute this blackbody-like emission component and many other differences between the two SNe to a small amount of additional H in SN 2011hw, analogous to the small H mass that makes SNe IIb differ from SNe Ib. Slower speeds in the CSM and somewhat elevated H content suggest a connection between SN 2011hw's progenitor and Ofpe/WN9 stars, which have been associated with luminous blue variables (LBVs) in their hot quiescent phases, and are H poor - but not H free like classical Wolf-Rayet (WR) stars. Comparisons between SN 2011hw and SN 2006jc can be largely understood if their progenitors exploded at different points in the transitional evolution from an LBV to a WR star.

Original languageEnglish (US)
Pages (from-to)1905-1915
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume426
Issue number3
DOIs
StatePublished - Nov 1 2012

Keywords

  • Supernovae:general
  • stars:winds, outflows
  • supernovae:individual:sn 2006jc
  • supernovae:individual:sn 2011hw

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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