Influence of Interstellar and Atmospheric Extinction on Light Curves of Eclipsing Binaries

Abstract

Interstellar and atmospheric extinctions redden the observational photometric data and they should be handled rigorously. This paper simulates the effect of reddening for the modest case of two main sequence T₁ = 6500 K and T₂ = 5500 K components of a detached eclipsing binary system. It is shown that simply subtracting a constant from measured magnitudes (the approach often used in the field of eclipsing binaries) to account for reddening should be avoided. Simplified treatment of the reddening introduces systematics that reaches ≈0.01 mag for the simulated case, but can be as high as ≈0.2 mag for, e.g., B8 V-K4 III systems. With rigorous treatment, it is possible to uniquely determine the colour excess value E(B – V) from multi-colour photometric light curves of eclipsing binaries.