SN Hunt 248: A super-Eddington outburst from a massive cool hypergiant

Jon C. Mauerhan, Schuyler D. Van Dyk, Melissa L. Graham, Wei Kang Zheng, Kelsey I. Clubb, Alexei V. Filippenko, Stefano Valenti, Peter Brown, Nathan Smith, D. Andrew Howell, Iair Arcavi

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

We present observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multistage outburst in 2014 May. The '2014a' discovery brightening exhibited an absolute magnitude of M ≈ -12 and the spectral characteristics of a cool, dense outflow, including P Cygni lines of Fe II, HI, and Na I, and line blanketing from metals. The source rapidly climbed and peaked at M ≈ -15 mag after two additional weeks. During this bright '2014b' phase the spectrum became dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4 × 105 L) variable precursor star. Its location on the Hertzsprung-Russell diagram is consistent with a massive (Minit ≈ 30M) cool hypergiant having an∼ extremely dense wind and an Eddington ratio (∼) just below unity. At the onset of the 2014a brightening, however, the object was super-Eddington (∼ = 4-12). The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable stars (LBVs). This lends support to the hypothesis that some cool hypergiants, such as ρ Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like η Car.

Original languageEnglish (US)
Pages (from-to)1922-1934
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume447
Issue number2
DOIs
StatePublished - Feb 21 2015

Keywords

  • Circumstellar matter - stars
  • Evolution - supernovae
  • General - supernovae
  • Individual
  • Outflows
  • Sn hunt 248 - stars
  • Winds

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Mauerhan, J. C., Van Dyk, S. D., Graham, M. L., Zheng, W. K., Clubb, K. I., Filippenko, A. V., Valenti, S., Brown, P., Smith, N., Andrew Howell, D., & Arcavi, I. (2015). SN Hunt 248: A super-Eddington outburst from a massive cool hypergiant. Monthly Notices of the Royal Astronomical Society, 447(2), 1922-1934. https://doi.org/10.1093/mnras/stu2541