Journal Article

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

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

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 389, issue 2, pages 955-966
Published in print September 2008 | ISSN: 0035-8711
Published online September 2008 | e-ISSN: 1365-2966 | DOI:
The Type IIb SN 2008ax: spectral and light curve evolution

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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 Hα is observed at higher velocities in SN 2008ax than in SN 1993J.

Keywords: supernovae: general; supernovae: individual: SN 2008ax; supernovae: individual: SN 1993J; galaxies: individual: NGC 4490

Journal Article.  6562 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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