The type IIb SN 2008ax: Spectral and light curve evolution

Journal article

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. © 2008 RAS.

Authors: Pastorello, A; Kasliwal, M; Crockett, R; Valenti, S; Arbour, R

• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 389
• Issue: 2
• Pages: 955-966
• Publication date: 2008-09-01
• DOI: 10.1111/j.1365-2966.2008.13618.x
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: Supernovae: general; Galaxies: individual: NGC 4490; Supernovae: individual: SN 1993J; Supernovae: individual: SN 2008ax