Emission-line profiles in SNe Ib/c – Probing the ejecta geometry

摘要

To constrain the ejecta geometry of stripped-envelope core-collapse SNe, we investigatenearly 100 nebular spectra of 39 objects, several previously unpublished. We perform a Gauss-fittingof [O_I]λλ6300, 6364 in all spectra, and on the basis of best-fit parameters organise the objectsinto morphological classes. We conclude that at least 40% of all SNe Ib/c must be aspherical. Insome SNe, the [O_I] line exhibits a variety of shifted secondary peaks or shoulders, interpreted asblobs of matter ejected at high velocity. The profile of Mg_I]λ4571 generally resembles that of [OI]λλ6300, 6364, suggesting negligible contamination from other lines and confirming that O and Mgare similarly distributed within the ejecta.