Observation of x-ray pulser A 0535+26

The outburst of the X-ray pulser A 0535+26 was observed, and the results of data analysis are reported in this paper. The outburst was detected on October 2, 1980, by the SVC 1/2 counter loaded on 'Hakucho'. The maximum of X-ray intensity was seen on October 10, then the intensity began to reduce, and the intensity on November 3 was not detectable. The energy spectrum of X-ray became soft for the period of 25 days. The outbursts of A 0535+26 have occurred at intervals of about 110 days. The pulse period on the October 9 was 103.67 sec, and became 103.61 sec on October 22. The period was constant for the period from October 22 to November 3. Discussion on this variation is presented. The analysis of pulse delay time was performed. The delay time data were on a smooth delay curve. This shows a Doppler effect of the revolution of A 0535+26. The eccentricity of the orbit of revolution was given by the chi-square analysis. (Kato, T.)