We investigated the period variation for 79 eclipsing binary systems using 20 years (1990-2009) of EROS, Macho, and OGLE survey observations. We discovered 9 apsidal motions, 8 mass transfers, 5 period increasing and decreasing systems, 12 light-travel-time effects, 5 eccentric systems and 40 other systems showing no period variations. We select 3 representative eclipsing binary systems; EROS 1052 for apsidal motion, EROS 1056 for mass transfer, and EROS 1037 for the light-travel-time effect. We determine the period variation rate (dP/dt), orbital parameters of the 3rd body (e3, ω3, f(m3), P3, T3), apsidal motion parameters (dω/dt, U, Ps, Pa, e) and apsidal motion period by analyzing the light curves and O-C diagrams.

ABSTRACT
1. INTRODUCTION
2. LIGHT CURVES ANALYSIS
3. PERIOD VARIATIONS
    3.1. EROS 1037
    3.2. EROS 1052
    3.3. EROS 1056
4. SUMMARY
REFERENCES

• P. Rittipruk(Department of Astronomy and Space Science, Sejong University)
• K. S. Hong(Korea Astronomy and Space Science Institute)
• Y. W. Kang(Department of Astronomy and Space Science, Sejong University)