Breger observed this star for one night in 1966 to find its variability. However, he failed to find any periodic variations within the errors of measurement. Since then some astronomers observed it and obtained some data sets. They discovered the variability of this star. The amplitude of single frequency was 0.0059 mag in 1969, 0.0082 mag in 1972, 0.0078 in 1973, 0.0067 mag during 1975-1979. The author observed this star from 1991-1992 with the 60 cm telescope at Xinglong Station of Beijing Astronomical Observatory and made period analyses. Two pulsation periods were obtained. The amplitude of first frequency was increasing to 0.0116 mag. And its comprehensive amplitude of two frequencies sometimes reached about 0.2 mag. As indicated above, tau Peg is such an example of delta Scuti star which not only started to pulsate after 1966, but also might increase its amplitude of pulsation from year to year.
IAU Joint Discussion
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