Emission line
= Emission line
{title2=$I_{\rm line}>I_{\rm continuum}$}
An <emission line> is a localized excess of <specific intensity> above the continuum. Heated chromospheric material can give a line source above the photospheric continuum source. Optically thin circumstellar gas can also add line photons through recombination or collisional excitation. Such line formation need not obey a thermal photospheric source prescription.