*Astron. Astrophys. Suppl. Ser.* **132**, 45-54

**A. Peraiah - M. Srinivasa Rao **

**Send offprint request: **A. Peraiah

e-mail: anna@iiap.ernet.in

Indian Institute of Astrophysics, Koramangala, Bangalore-560034, India

Received March 20, 1997; accepted March 24, 1998

We studied the effects of irradiation on the line formation in
the expanding atmospheres of the components of close binary
systems. We considered a two-level atom approximation in
Non-LTE situation. The thickness of the atmosphere is assumed to
be twice that of the stellar radius. Expansion velocities are
assumed to be as large as 50 mean thermal units. We have computed the
lines using total optical depths 10^{3}, 10^{4} and 10^{5} at the line
centre. The irradiation from the secondary is assumed to be one,
five and ten times the self radiation. The line fluxes in the
line of sight are calculated by using the total source function
which is the sum of the source functions due to self radiation
and that due to irradiation. We notice that the expansion of
the medium produces *P* Cygni type profiles and the irradiation
enhances the emission in the lines although the equivalent
widths reduce considerably.

**Key words: **radiative transfer -- lines: formation;
profiles -- binaries: close

- 1 Introduction
- 2 Brief description of the method of calculations
- 3 Results and discussion
- Appendix A
- Appendix B
- 6 Figures in electronic form only
- References

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