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The existence of an additional body around a binary system can be detected bythe help of the light-travel time effect. Due to the motions of binary and thecompanion stars around the common mass center of the ternary system, thelight-time effect produces an irregularity on the eclipse timings. Monitoringthe variations in these timings, sub-stellar or planet companions orbitingaround the binary system can be identified. In this paper, additional bodiesorbiting the Algol type binary DI Peg are examined by using the archivaleclipse timings including our CCD data observed at the Ankara UniversityKreiken Observatory. More than five hundred minimum times equivalent to aroundnine decades are employed to identify the orbital behavior of the binarysystem. The best fit to the timings shows that the orbital period of DI Peg hasvariation due to an integration of two sinusoids with the periods of $P_3 =49.50\pm0.36$ yr and $P_4 = 27.40\pm0.24$ yr. The orbital change is thought tobe most likely due to the existence of two M-type red dwarf companions with themasses of $M_3 =0.213 \pm 0.021$ M$_\odot$ and $M_4 = 0.151 \pm 0.008$M$_\odot$, assuming that the orbits of additional bodies are co-planar with theorbit of the binary system. Also, the residuals of two sinusoidal fits stillseem to show another modulation with the period of roughly $P = 19.5$ yr. Theorigin of this modulation is not clear and more observational data are requiredto reveal if the periodicity is caused by another object gravitationallybounded to the system.

The Period Analysis of the Hierarchical System DI Peg