Multiple scattering and the phase variation of equivalent widths for phase functions of typeP(cos?)=?+?1 P 1(cos?)+?2 P 2(cos?)

Abstract

After computing theH-functions for 21 different phase functions corresponding to various combinations of\(\bar \varpi \)1=ϖ1/ϖand\(\bar \varpi \)2=ϖ2/ϖalong with 15 values of ϖ, variations of equivalent widths with phase angle have been obtained for these cases for lines with Lorentz profile with the continuum albedo ϖc=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.