Spectral evolution of the extraordinary type iin supernova 2006gy

Nathan Smith, Ryan Chornock, Jeffrey M. Silverman, Alexei V. Filippenko, Ryan J. Foley

Research output: Contribution to journalArticle

121 Scopus citations

Abstract

We present a detailed analysis of the extremely luminous and long-lasting Type IIn supernova (SN) 2006gy using spectra obtained between days 36 and 237 after explosion. We derive the temporal evolution of the effective temperature, radius, blast-wave and SN-ejecta expansion speeds, and bolometric luminosity, as well as the progenitor wind density and total swept-up mass overtaken by the shock. SN 2006gy can be interpreted in the context of shock interaction with a dense circumstellar medium (CSM), but with quite extreme values for the CSM mass of ∼20 M and SN explosion kinetic energy of at least 5 × 1051 erg. A key difference between SN 2006gy and other SNe IIn is that, owing to its large amount of swept-up mass, the interaction region remained opaque much longer. At early times, Hα emission-line widths suggest that the photosphere is ahead of the shock, and photons diffuse out through the opaque CSM shell. The pivotal transition to optically thin emission occurs around day 110, when we start to see a decrease in the blackbody radius RBB and strengthening tracers of the post-shock shell. From the evolution of pre-shock velocities, we deduce that the CSM was ejected by the progenitor star in a 1049 erg precursor event ∼8 yr before the explosion. The large CSM mass definitively rules out models involving stars with initial masses of 10 M. If the pre-SN mass budget also includes the likely SN ejecta mass of 10–20 M and the distant >10 M shell inferred from a light echo, then even massive MZAMS = 30–40 M progenitor stars are inadequate. At roughly solar metallicity, substantial mass loss probably occurred during the star’s life, so SN 2006gy’s progenitor is more consistent with sequential giant luminous blue variable eruptions or pulsational pair-instability ejections in extremely massive stars with initial masses above 100 M. This requires significant revision to current paradigms of massive-star evolution.

Original languageEnglish (US)
Pages (from-to)856-883
Number of pages28
JournalAstrophysical Journal
Volume709
Issue number2
DOIs
StatePublished - Feb 2010
Externally publishedYes

Keywords

  • Circumstellar matter
  • Stars: evolution
  • Supernovae: individual (SN 2006gy)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Smith, N., Chornock, R., Silverman, J. M., Filippenko, A. V., & Foley, R. J. (2010). Spectral evolution of the extraordinary type iin supernova 2006gy. Astrophysical Journal, 709(2), 856-883. https://doi.org/10.1088/0004-637X/709/2/856