Equivalent width

The equivalent width is a measure of the Astro spectroscopy for the thickness of lines in an absorption spectrum. It provides a size represents that does not depend on the characteristics of the apparatus used, and therefore is well suited for comparison between different measurements.

Calculation

It starts from a background source of constant intensity, which is weakened by the foreground material to a certain frequency. The entire area between the background source with intensity and the actual intensity profile is given as

The equivalent width is then

And geometrically corresponds to the side length of the rectangle having the same area as the absorbed intensity, wherein the second side is given by.

Swell

  • David F. Gray, The Observation and Analysis of Stellar Photospheres, Third Edition, Cambridge 2005, ISBN 0-521-85186-6
  • Spectroscopy
  • Observation method of Astronomy
Astronomical spectroscopy Absorption spectroscopy#Absorption spectrum
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