The existence of an additional body around a binary system can be detected by the help of the light-travel time effect .
Due to the motions of binary and the companion stars around the common mass center of the ternary system , the light-time effect produces an irregularity on the eclipse timings .
Monitoring the variations in these timings , sub-stellar or planet companions orbiting around the binary system can be identified .
In this paper , additional bodies orbiting the Algol type binary DI Peg are examined by using the archival eclipse timings including our CCD data observed at the Ankara University Kreiken Observatory .
More than five hundred minimum times equivalent to around nine decades are employed to identify the orbital behavior of the binary system .
The best fit to the timings shows that the orbital period of DI Peg has variation due to an integration of two sinusoids with the periods of P _ { 3 } = 49.50 \pm 0.36 yr and P _ { 4 } = 27.40 \pm 0.24 yr .
The orbital change is thought to be most likely due to the existence of two M-type red dwarf companions with the masses 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 the orbit of the binary system .
Also , the residuals of two sinusoidal fits still seem to show another modulation with the period of roughly P = 19.5 yr .
The origin of this modulation is not clear and more observational data are required to reveal if the periodicity is caused by another object gravitationally bounded to the system .