Astrophysics (Index)About

bracket notation

(bracket abundance notation, abundance notation)
(notation for a comparison of an abundance ratio with that of the Sun)

A bracket notation is used to characterize abundances of nuclear species within an astronomical object, specifically, the ratio of the abundances of two specific elements (chemical abundance ratios or abundance ratios). For example, a particular body's [Fe/He] is a measure of the ratio of its number-count of iron atoms with that of its helium atoms. The meaning:

[Fe/He] means
log10(NFe/NHe)body - log10(NFe/NHe)Sun

If a body's [Fe/He] is 0, then its ratio of iron to helium is identical to that of the Sun. If it is 1, then its ratio is ten times that of the Sun, and if it is -3, then its ratio is a thousandth of that of the Sun. Sometimes rather than a specific element, a symbol for some set of elements is specified; for example, M or Z for all metals, or α (alpha) for all alpha elements.


(atoms,measure)
Further reading:
http://burro.case.edu/Academics/Astr222/Galaxy/Structure/metals.html
http://www-star.st-andrews.ac.uk/~kdh1/ce/ce11.pdf
http://astronomy.nmsu.edu/holtz/a555/pdf/lecture17_A555_F22_stellarEvolutionHR.pdf
https://ui.adsabs.harvard.edu/abs/2013pss5.book...55F/abstract
https://ui.adsabs.harvard.edu/abs/2002IAUS..187...91E/abstract

Referenced by pages:
alpha-enhanced
extremely metal poor galaxy (XMPG)
iron (Fe)
metallicity (Z)
Population III (Pop III)
rocky planet
stellar population
[α/Fe] versus [Fe/H] diagram

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