PS1-12sk is a peculiar supernova from a he-rich progenitor system in a brightest cluster galaxy environment

N. E. Sanders, A. M. Soderberg, R. J. Foley, R. Chornock, D. Milisavljevic, R. Margutti, M. R. Drout, M. Moe, E. Berger, W. R. Brown, R. Lunnan, S. J. Smartt, M. Fraser, R. Kotak, L. Magill, K. W. Smith, D. Wright, K. Huang, Y. Urata, J. S. MulchaeyA. Rest, D. J. Sand, L. Chomiuk, A. S. Friedman, R. P. Kirshner, G. H. Marion, J. L. Tonry, W. S. Burgett, K. C. Chambers, K. W. Hodapp, R. P. Kudritzki, P. A. Price

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


We report on our discovery and observations of the Pan-STARRS1 supernova (SN) PS1-12sk, a transient with properties that indicate atypical star formation in its host galaxy cluster or pose a challenge to popular progenitor system models for this class of explosion. The optical spectra of PS1-12sk classify it as a Type Ibn SN (SN Ibn; cf. SN 2006jc), dominated by intermediate-width (3 × 103 km s-1) and time variable He I emission. Our multi-wavelength monitoring establishes the rise time dt ∼ 9-23 days and shows an NUV-NIR spectral energy distribution with temperature ≳ 17 × 103 K and a peak magnitude of Mz = -18.88 ± 0.02 mag. SN Ibn spectroscopic properties are commonly interpreted as the signature of a massive star (17-100 M) explosion within an He-enriched circumstellar medium. However, unlike previous SNe Ibn, PS1-12sk is associated with an elliptical brightest cluster galaxy, CGCG 208-042 (z = 0.054) in cluster RXC J0844.9+4258. The expected probability of an event like PS1-12sk in such environments is low given the measured infrequency of core-collapse SNe in red-sequence galaxies compounded by the low volumetric rate of SN Ibn. Furthermore, we find no evidence of star formation at the explosion site to sensitive limits (Σ ≲ 2 × 10-3 M yr-1 kpc-2). We therefore discuss white dwarf binary systems as a possible progenitor channel for SNe Ibn. We conclude that PS1-12sk represents either a fortuitous and statistically unlikely discovery, evidence for a top-heavy initial mass function in galaxy cluster cooling flow filaments, or the first clue suggesting an alternate progenitor channel for SNe Ibn.

Original languageEnglish (US)
Article number39
JournalAstrophysical Journal
Issue number1
StatePublished - May 20 2013
Externally publishedYes


  • galaxies: clusters: general
  • galaxies: star formation
  • stars: winds, outflows-supernovae: general
  • supernovae: individual (PS1-12sk)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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