THE PROPERTIES OF THE UNIQUE TYPE IbSUPERNOVA 2005bf AND IMPLICATIONS FOR THEDIFFERENCE BETWEEN TYPE Ib/c SUPERNOVAE

摘要

The properties of the unique Type Ib supernova (SN) 2005bf are studied throughthe theoretical modeling of the early phase spectra and the light curve. The highvelocity FeII lines in the earliest spectra are not the consequence of a jet-likeexplosion, but are naturally explained by a lower ionization state of Fe in theoutermost layer due to the existence of the hydrogen. The velocities of the Helines measured from the position of the absorption minimum increase with time.Such a behavior is unprecedented, and can be understood if ~(56)Ni is not fully mixedwith the He layer. An increasing deposition of γ-rays in the He layer is necessary toproduce more and more non-thermal electrons. Therefore it is also suggested thatthe C+O layer between ~(56)Ni and the He layer is not very thick. The progenitorsof Type Ib supernovae (SNe) and Type Ic SNe are briefly discussed by comparingSN 2005bf with other Type Ib/c SNe. We suggest that the mixig of ~(56)Ni plays animportant role to make the difference between Type Ib SNe and Type Ic SNe.