We present the rst period variation study for the Algol eclipsing binary V346 Cyg by constructing the (O-C) residual diagram using all the available precise minima times. We conclude that the period variation can be explained by a sine{like variation due to the presence of a third body orbiting the binary in about 68:89  4:69 years, together with a long-term orbital period decrease (dP=dt = -1:23 x 10-7day=yr) that can be interpreted to be due to slow mass loss from the δ-Scuti primary component. The sinusoidal variation may also be explained by using the the Applegate (1992) mechanism involving cyclic magnetic activity due to star-spots on the secondary component. The present preliminary solution needs more precise photometric observations to be conrmed.

Abstract
1. INTRODUCTION
2. PERIOD VARIATION STUDY
    2.1. Mass Loss
    2.2. Third Body Hypothesis
    2.3. Magnetic Activity
    2.4. δ Scuti Light Time Effect
3. DISCUSSION
4. CONCLUSIONS
REFERENCES

• MAGDY HANNA(National Research Institute of Astronomy and Geophysics (NRIAG)) CORRESPONDING AUTHOR