COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 532 Konkoly Observatory Budapest 1971 March 20 THE SECONDARY PERIOD OF THE VARIABLE STAR SW PISCIUM The variable star SW Piscium (of RR Lyrae type) has been observed photographically at the Observatory of the University of Cluj (telescope : D=50 cm., F=250 cm.), from September 1964 to October 1988, Fifteen light maxima were obtained showing sensible variations in phase. In the table below, the first column contains the times of the observed maxima and the second column the O-C values computed with the following elements: Max.hel. = J.D.2438652.443 + 0.521265d.E determined by the author, and published in (1) ----------------------- J.D.mag.hel. O-C ----------------------- 2438643.568 -0.013d 38651.402 +0.002 38652.443 0.000 38654.534 +0.006 38666.521 +0.004 38675.363 -0.016 38684.235 -0.005 38698.320 +0.006 38699.364 +0.007 38700.405 +0.006 38782.223 -0.015 39375.441 +0.003 39388.477 +0.008 39389.521 +0.009 39410.359 -0.003 ----------------------- In the Figure the O-C differences (crosses) are plotted against Epoch E. The oscillations of maxima in phase can be represented by a formula (the continuous line in Figure): O-C = 0.0132d sin 5.440d(E+2) - 0.002d This formula suggests a secondary period P_b = 34.5d. [FIGURE 1] The oscillations in height of maxima may be also present, but the accuracy of the photographic observations does not allow to determine their amplitude. Further observations will be necessary in order to determine the secondary period more exactly and to study the Blashko-effect. LITERATURE 1. Tsesevich. V.P.; Szczepanowska,A.: Rocznik Astronomiczny Obserw. Krakow No. 39, 115, 1967. University of Cluj, Roumania V. URECHE