# Bipolar Supernova Explosions: Nucleosynthesis & Implication on Abundances in Extremely Metal-Poor Stars

Source: [Bipolar Supernova Explosions: Nucleosynthesis & Implication on Abundances in Extremely Metal-Poor Stars](<https://www.sota2.com/research/paper/68fa26002c2a3760193b5b6c>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-24T11:05:44.216Z

Authors: K. Maeda, K. Nomoto

Published: 2003-04-09T19:45:04.000Z

## Abstract

Hydrodynamics and explosive nucleosynthesis in bipolar supernova explosions are examined to account for some peculiar properties of hypernovae as well as peculiar abundance patterns of metal-poor stars. The explosion is supposed to be driven by bipolar jets which are powered by accretion onto a central remnant. We explore the features of the explosions with varying progenitors' masses and jet properties. The outcomes are different from conventional spherical models. (1) In the bipolar models, Fe-rich materials are ejected at high velocities along the jet axis, while O-rich materials occupy the central region whose density becomes very high as a consequence of continuous accretion from the side. This configuration can explain some peculiar features in the light curves and the nebular spectra of hypernovae. (2) Production of $^{56}$Ni tends to be smaller than in spherical thermal bomb models. To account for a large amount of $^{56}$Ni observed in hypernovae, the jets should be initiated when the compact remnant mass is still smaller than $2-3\\msun$, or the jets should be very massive and slow. (3) Ejected isotopes are distributed as follows in order of decreasing velocities: $^{64}$Zn, $^{59}$Co, $^{56}$Fe, $^{44}$Ti, and $^{4}$He at the highest velocities, $^{55}$Mn, $^{52}$Cr, $^{32}$S, and $^{28}$Si at the intermediate velocities, and $^{24}$Mg, $^{16}$O at the lowest velocities. (4) The abundance ratios (Zn, Co)/Fe are enhanced while the ratios (Mn, Cr)/Fe are suppressed. This can account for the abundance pattern of extremely metal-poor stars. These agreements between the models and observations suggest that hypernovae are driven by bipolar jets and have significantly contributed to the early Galactic chemical evolution.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/astro-ph/0304172>)

[PDF](<https://arxiv.org/pdf/astro-ph/0304172.pdf>)