8 research outputs found
First Stars -- Type Ib Supernovae Connection
The very peculiar abundance patterns observed in extremely metal-poor (EMP)
stars can not be explained by ordinary supernova nucleosynthesis but can be
well-reproduced by nucleosynthesis in hyper-energetic and hyper-aspherical
explosions, i.e., Hypernovae (HNe). Previously, such HNe have been observed
only as Type Ic supernovae. Here, we examine the properties of recent Type Ib
supernovae (SNe Ib). In particular, SN Ib 2008D associated with the luminous
X-ray transient 080109 is found to be a more energetic explosion than normal
core-collapse supernovae. We estimate that the progenitor's main sequence mass
is 20--25 M_sun and a kinetic energy of explosion is ~ 6 x 10^{51} erg. These
properties are intermediate between those of normal SNe and hypernovae
associated with gamma-ray bursts. Such energetic SNe Ib can make important
contribution to the chemical enrichment in the early Universe.Comment: 7 pages, 5 figure
Chemical Yields from Supernovae and Hypernovae
We review the final stages of stellar evolution, supernova properties, and
chemical yields as a function of the progenitor's mass M. (1) 8 - 10 Ms stars
are super-AGB stars when the O+Ne+Mg core collapses due to electron capture.
These AGB-supernovae may constitute an SN 2008S-like sub-class of Type IIn
supernovae. These stars produce little alpha-elements and Fe-peak elements, but
are important sources of Zn and light p-nuclei. (2) 10 - 90 Ms stars undergo
Fe-core collapse. Nucleosynthesis in aspherical explosions is important, as it
can well reproduce the abundance patterns observed in extremely metal-poor
stars. (3) 90 - 140 Ms stars undergo pulsational nuclear instabilities at
various nuclear burning stages, including O and Si-burning. (4) 140 - 300 Ms
stars become pair-instability supernovae, if the mass loss is small enough. (5)
Stars more massive than 300 Ms undergo core-collapse to form intermediate mass
black holes.Comment: 13 pages, 10 figures. Published in the Proceedings of IAU Symposium
No. 254 "The Galaxy Disk in Cosmological Context" (2009), eds. J. Andersen,
J. Bland-Hawthorn, and B. Nordstrom (Cambridge University Press), pp. 355-36