Multiple scattering and the phase variation of equivalent widths for phase functions of type P(cosθ)=ω+ω₁P₁(cosθ)+ω₂P₂(cosθ)

Abstract

After computing the H-functions for 21 different phase functions corresponding to various combinations of w^-_l = w_l/w and w^-₂ = w₂/w along with 15 values of w, variations of equivalent widths with phase angle have been obtained for these cases for lines with Lorentz profile with the continuum albedo w_c= 0.99. It is found that: (i) The absolute values of equivalent width at any phase angle are inversely related to the value of phase function for that angle; (ii) The usual inverse phase effect occurs whenever the phase function has a maximum at α= 0 and a dip somewhere between α= 0 and α= 180; (iii) Whenever the phase function has minima at α= 0 and α= 180 one obtains an incipient inverse phase effect at large phase angles; and (iv) The total variations are larger for weaker lines.