Detection of superhumps in the cataclysmic variable V378 Peg (PG 2337+300)

摘要

The cataclysmic variable V378 Peg is known since 15 years. Although V378 Peg is a rather bright star (14 mag), it underwent no detailed study. We performed photometric observations of V378 Peg during 75 h with the goal to detect periodic brightness variations. The obtained light-curves clearly showed changes with a period of about 3 h. The Fourier analysis reveals that this oscillation occurs with a period of 3.238 h and a semiamplitude of 0.07 mag. Although the detected oscillation possesses certain coherence, it appears to have a slightly unstable period or phase. Therefore, the detected period cannot be the orbital period of the V378 Peg system. Because such instability is typical of superhumps, we must consider the detected oscillation as superhumps. Furthermore, V378 Peg shows no outbursts and has to be a nova-like variable rather than a dwarf nova. Hence, the detected superhumps have to be regarded as permanent superhumps. Because superhump periods in cataclysmic variables are close to orbital periods, we can find the place of V378 Peg in the orbital period distribution of cataclysmic variables. V378 Peg is a permanent superhump system above the upper edge of the 2-3 h period gap in the orbital period distribution.