The Type IIb SN 2008ax: spectral and light curve evolution

Andrea Pastorello, M.M. Kasliwal, Rhonda Crockett, Stefano Valenti, R. Arbour, K. Itagaki, S. Kaspi, A. Gal-Yam, Stephen Smartt, R. Griffith, Kathrina Maguire, E.O. Ofek, N. Seymour, D. Stern, W. Wiethoff

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87 Citations (Scopus)


We present spectroscopy and photometry of the He-rich supernova (SN) 2008ax. The early-time spectra show prominent P-Cygni H lines, which decrease with time and disappear completely about 2 months after the explosion. In the same period He I lines become the most prominent spectral features. SN 2008ax displays the ordinary spectral evolution of a Type IIb supernova. A stringent pre-discovery limit constrains the time of the shock breakout of SN 2008ax to within only a few hours. Its light curve, which peaks in the B band about 20 d after the explosion, strongly resembles that of other He-rich core-collapse supernovae. The observed evolution of SN 2008ax is consistent with the explosion of a young Wolf-Rayet (of WNL type) star, which had retained a thin, low-mass shell of its original H envelope. The overall characteristics of SN 2008ax are reminiscent of those of SN 1993J, except for a likely smaller H mass. This may account for the findings that the progenitor of SN 2008ax was a WNL star and not a K supergiant as in the case of SN 1993J, that a prominent early-time peak is missing in the light curve of SN 2008ax, and that H alpha is observed at higher velocities in SN 2008ax than in SN 1993J.
Original languageEnglish
Pages (from-to)955-966
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Sep 2008

ASJC Scopus subject areas

  • Space and Planetary Science


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