Massive stars exploding in a He-rich circumstellar medium - V. Observations of the slow-evolving SN Ibn OGLE-2012-SN-006

A. Pastorello*, L. Wyrzykowski, S. Valenti, J. L. Prieto, S. Kozlowski, A. Udalski, N. Elias-Rosa, A. Morales-Garoffolo, J. P. Anderson, S. Benetti, M. Bersten, M. T. Botticella, E. Cappellaro, G. Fasano, M. Fraser, A. Gal-Yam, M. Gillone, M. L. Graham, J. Greiner, S. HachingerD. A. Howell, C. Inserra, J. Parrent, A. Rau, S. Schulze, S. J. Smartt, K. W. Smith, M. Turatto, O. Yaron, D. R. Young, M. Kubiak, M. K. Szymanski, G. Pietrzynski, I. Soszynski, K. Ulaczyk, R. Poleski, P. Pietrukowicz, J. Skowron, P. Mroz

*Corresponding author for this work

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17 Citations (Scopus)

Abstract

We present optical observations of the peculiar Type Ibn supernova (SN Ibn) OGLE-2012-SN-006, discovered and monitored by the Optical Gravitational Lensing Experiment-IV survey, and spectroscopically followed by Public ESO Spectroscopic Survey of Transient Objects (PESSTO) at late phases. Stringent pre-discovery limits constrain the explosion epoch with fair precision to JD = 245 6203.8 +/- 4.0. The rise time to the I-band light-curve maximum is about two weeks. The object reaches the peak absolute magnitude M-I = -19.65 +/- 0.19 on JD = 245 6218.1 +/- 1.8. After maximum, the light curve declines for about 25 d with a rate of 4 mag (100 d)(-1). The symmetric I-band peak resembles that of canonical Type Ib/c supernovae (SNe), whereas SNe Ibn usually exhibit asymmetric and narrower early-time light curves. Since 25 d past maximum, the light curve flattens with a decline rate slower than that of the Co-56-Fe-56 decay, although at very late phases it steepens to approach that rate. However, other observables suggest that the match with the Co-56 decay rate is a mere coincidence, and the radioactive decay is not the main mechanism powering the light curve of OGLE-2012-SN-006. An early-time spectrum is dominated by a blue continuum, with only a marginal evidence for the presence of He I lines marking this SN type. This spectrum shows broad absorptions bluewards than 5000 angstrom, likely O II lines, which are similar to spectral features observed in superluminous SNe at early epochs. The object has been spectroscopically monitored by PESSTO from 90 to 180 d after peak, and these spectra show the typical features observed in a number of SN 2006jc-like events, including a blue spectral energy distribution and prominent and narrow (v(FWHM) approximate to 1900 km s(-1)) He I emission lines. This suggests that the ejecta are interacting with He-rich circumstellar material. The detection of broad (10(4) km s(-1)) O I and Ca II features likely produced in the SN ejecta (including the [OI] lambda lambda 6300,6364 doublet in the latest spectra) lends support to the interpretation of OGLE-2012-SN-006 as a core-collapse event.

Original languageEnglish
Pages (from-to)1941-1953
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume449
Issue number2
Early online date31 Mar 2015
DOIs
Publication statusPublished - 11 May 2015

Keywords

  • supernovae: general
  • supernovae: individual: OGLE-2012-SN-006
  • supernovae: individual: SN 2006jc
  • supernovae: individual: SN 2010al
  • DUST FORMATION
  • IIN SUPERNOVA
  • LIGHT CURVES
  • 2006JC
  • EXPLOSION
  • 2010JL
  • PROGENITORS
  • TRANSIENTS
  • SN-2006JC
  • BRIGHTEST

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