Nucleosynthesis and light curve of Supernovae Ia

[elouisa]

Hi all,

I am trying to understand the connection between the specific nucleosynthesis that occurs in each step of the explosion mechanism of type Ia supernova (SN Ia).

Let´s see if I got it right, type Ia SN is the complete disruption of a white dwarf(WD) once it passes through the deflagration and detonation phases. Before those phases, as density and temperature increases in the WD, carbon, oxygen and silicon burns. These would be hydrostatic nuclear reactions, right?. Now, my questions are:
Which are the specific nuclear reactions occurring at the degflagration and detonation phase?
Which are the specific so called explosive nucleosynthesis happening in this type of supernova?
Do all the products of the silicon burning are ¨cooked¨ before the explosion?
Which are the specific elements produced during the deflagration and detonation phases?

And about the light curve, why the Si II line is so intense?


Thank you very much!

 

[twofish-quant]

Which are the specific nuclear reactions occurring at the degflagration and detonation phase?

This is a *VERY* complicated question. The way that people simulate everything is by having a reaction network which calculates the speed at which one isotope gets converted to another isotope a given temperature and pressure. Typically these calculations simulate several hundred different nuclear reactions.

http://arxiv.org/abs/astro-ph/0505417

Do all the products of the silicon burning are ¨cooked¨ before the explosion?

No. The explosion cooks them. There's no new silicon in a supernova Ia before the explosion. The silicon gets produced during the explosion.

Which are the specific elements produced during the deflagration and detonation phases?

Rather complicated question. What happens is that because detonation is a more violent process, you end up with heavier isotopes (iron and cobalt) than with deflagration. It's not so much specific elements as ratios between different isotopes. Also, you see fast moving iron and cobalt in Ia's which says that there is some sort of detonation, but if the whole explosion were a detonation you'd end up with too much heavy element.

And about the light curve, why the Si II line is so intense?

Because large amounts of C+O fuse in the explosion to form silicon. This contrasts with Ib's and Ic's which are basically type II supernova whose hydrogen envelope has been stripped, and in which there isn't the large amount of silicon because it's already been burned to iron.

 

[Emustrangler]

Because large amounts of C+O fuse in the explosion to form silicon. This contrasts with Ib's and Ic's which are basically type II supernova whose hydrogen envelope has been stripped, and in which there isn't the large amount of silicon because it's already been burned to iron.

To add, the least dense material in the WD at the surface burns to Si (denser burning leads to heavier nuclei, mostly Ni56). So not only is Si the product of the burning, but its concentrated at the surface, and so is a component of the photosphere right from the beginning.