Typically, a spectral type judged solely from hydrogen lines is intermediate.
[3][4] The chemical abnormalities are due to some elements which absorb more light being pushed towards the surface, while others sink under the force of gravity.
The following table lists some metallic-line stars in order of descending apparent visual magnitude.
A small number of Am stars show unusually late spectral types and particularly strong luminosity effects.
Later studies showed that the group was somewhat inhomogeneous, possibly coincidental, and recommended dropping use of the δ Delphini class in favour of a narrower class of ρ Puppis stars with relatively high luminosity and late spectral types.