S-Process
Slow Neutron Capture: A process in which heavy, stable, neutron-rich nuclei are synthesized from iron-peak elements by successive captures of free neutrons in a weak neutron flux, ...
S-PROCESS - Slow neutron capture by nuclei in massive stars. In the s-process, one starts with existing iron-group nuclei.
S-process - The process of building up massive nuclei in which neutrons are captured at a rate slower than the newly produced nuclei can undergo radioactive decay ...
S-Process: The absorption of neutrons by elements in massive stars, causing them to transform to other isotopes, and, through subsequent nuclear decay, into other elements.
The s-process explains the synthesis of stable nuclei up to and including bismuth-209, the heaviest known nonradioactive nucleus, but it cannot account for the heaviest nuclei, such as thorium-232, uranium-238, or plutonium-242.
R-process
S-process
Neutron radiation and the Sievert radiation scale
[edit] Neutron sources ...
HD 147513 A is a so-called young "Barium dwarf" (s-process element rich but comparatively carbon deficient) star that was probably enriched by an asymptotic branch giant (AGB) star (see Gacrux) but is now a very dim, white dwarf companion, ...
S type stars have photospheres with enhanced abundances of s-process elements.
The s-process slowly builds stable nuclear species up to A = 208 (time between captures about 10-100 years). It ends there, because any further capture of neutrons leads immediately to -decay back to lead or thallium.
This involves two processes; the slow neutron capture process (s-process) and the rapid neutron capture process (r-process).
S stars have excess amounts of zirconium and other elements produced by the s-process, and have their carbon and oxygen abundances closer to equal than is the case for M stars.
Recall too how neutron capture via the s-process can build heavier nuclei in massive stars. How are the heaviest nuclei such as those of lead, gold and uranium produced?
Heavy elements can also form in the cores of massive stars before they go supernova (s-process isotopes). Secondly, some elements beyond helium are formed in planetary nebulae. Some can also be formed through cosmic ray collisions.
 See also: Element, Star, Mass, Elements, Giant
  
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