We present optical and infrared spectra of SN 1999ex that reveal a clear example of an intermediate Type Ib/c case. This suggests a continuous spectroscopic sequence between Type Ib and Type Ic supernovae. We report UBVRIz photometric observations of SN 1999ex that started only one day after explosion, which permitted us to witness an elusive transient cooling phase that lasted 4 days. The initial cooling and subsequent radioactive heating produced a dip in the lightcurve which is consistent with explosion models involving core collapse of evolved massive helium stars, and inconsistent with lightcurves resulting from the thermonuclear runaway of compact white dwarfs.
@article{arxiv.astro-ph/0212368,
title = {Evidence for Core Collapse in the Type Ib/c SN 1999ex},
author = {Mario Hamuy and Maximilian Stritzinger and M. M. Phillips and Nicholas B. Suntzeff and Jose Maza and Philip A. Pinto},
journal= {arXiv preprint arXiv:astro-ph/0212368},
year = {2009}
}
Comments
6 pages, 4 figures, to appear in ``From Twilight to Highlight: The Physics of Supernovae'', Eds. W. Hillebrandt and B. Leibundgut, Springer Series ``ESO Astrophysics Symposia'', Berlin