Can iron form via processes like the r- or s-process?

[Teichii492]

TL;DR

Can iron form via processes other than during silicon burning? e.g. the r- or s-process

Hi,

I was wondering by what other methods iron can form in stars? Iron can form during silicon burning and i assume it can also form via the beta- decay of neutron rich isotopes around the iron peak? Are these athe only two processes that relate to the cosmogenesis of iron?

 

[mfb]

I'm certain there will be the occasional iron atom formed in these processes - but silicon burning produces so much more that it doesn't matter.
It might contribute to Fe-58 (0.3% of natural iron) and Fe-57 (2.1%).

Edit: Mn-56 has a half life of only 2.5 hours, so the s-process won't lead to Fe-57 and Fe-58.

 

[stefan r]

...Edit: Mn-56 has a half life of only 2.5 hours, so the s-process won't lead to Fe-57 and Fe-58.

Chrome 52 is stable. adding neutrons to cr 53, and then cr54 are still stable. One more gets Cr55 which then beta decays to Mn55 which is stable. One more neutron is Mn 56 which beta decays to Fe56. Then add neutrons to get Fe 57 and Fe 58.

Vanadium 51 is stable. add neutron for V52 which beta decays to Cr52. All isotopes of Ti are stable 46 to 50. and Ti51 decays to V51. Sc46 beta decays to Ti46. Ca 45 decays to Sc 45. You can keep working backwards all the way.

 

[mfb]

Is it still the s-process if you start with Fe-56 that has so much more important origins? Eh, whatever.
Surprisingly, Fe56+n -> Fe-57 releases energy.

 

[snorkack]

Whereas s-process skips Fe-54. How is Fe-54 formed?
Since Fe-59 has half-life 45 days, r-process forms Fe-60... which, however, has half-life 2,6 million years.

 

[stefan r]

Whereas s-process skips Fe-54. How is Fe-54 formed?
Since Fe-59 has half-life 45 days, r-process forms Fe-60... which, however, has half-life 2,6 million years.

Alpha process maybe. Ti-46 becomes Cr-50 becomes Fe-54. Photodisintegration of Nickel 58 might get the job done too. Pair instability supernova would have hydrogen present while temperatures are high enough to shove protons in there. So decay of Co-54.

I do not know what happens if you start the alpha process from Oxygen-18 instead of Oxygen-16.