COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 960 Konkoly Observatory Budapest 1975 January 24 BLAZHKO EFFECT IN THE RR LYRAE TYPE STAR WY DRACONIS The RR Lyrae type variable star, WY Draconis, little studied before, was observed photographically at the University Observatory of Cluj (by a Newton telescope of D=50 cm and F=250 cm) during the period 15. October 1959 - 9. October 1970. The investigation was proposed by Prof. W. Tsessevich. 36 maxima were obtained, giving the new elements of the star: Max. hel. = JD 2430786,5302 + 0d.5889466 E (1) +- 512 +-21 Observed maxima as well as the O-C differences given in the table prove a periodic variation of the period which could not be determined with certainty because of the sporadic observations. The observations gave evidence of a large variation in the height of maxima (about 0m,6) as well as a remarkable variation in the shape of the light curve. The light curves (Fig. 1) corresponding to JD 2439269 (Psi = 0.056) and JD 2439786 (Psi = 0.900) illustrate this variation. The brightness of 27 light maxima (m_{max}) and of 13 minima was determined with an accuracy of a few hundredths of magnitude. The period of variation in the height of the maxima was determined as : P_1 = 24.2823xP_0 = 14d,301. The time of maxima can be given by the formula : E = - 4955 + 24.2823(n+Psi) (2) where the epoch E corresponds to the elements (1) , n is the number of secondary cycles, taken from the initial epoch E_0=-4955, and Psi is the secondary phase taken as a fraction of the basic period P_0 = 0d.5889466. Values of m_{max} are plotted against the phase Psi in Fig. 2 showing, with some deviations, the periodicity of the variation of the light curve. A more accurate study of this phenomenon using more observations is hoped in the future. [FIGURE 1] [FIGURE 2] Max.hel. O-C n Psi m_{max} m_{min} JD 24... 36868.3040 +0.0042 0 0 11.94 13.62 Gh. Chis 36869.4610 -0.0167 0 0.0809 12.04 13.42 " 36895.4038 +0.0125 1 0.8050 12.01 - " 36898.3440 +0.0079 2 0.1006 - - " 38624.5415 +0.0030 122 0.8052 11.77 - I. Mihoc 38637.4980 +0.0026 123 0.7112 11.71 13.74 " 38697.5670 -0.0009 127 0.9115 11.95 13.61 " 38729.3680 -0.0037 130 0.1353 - - " 38938.4500 +0.0030 144 0.7553 11.14 - " 38948.4600 +0.0008 145 0.4476 - - " 39200.5217 -0.0063 163 0.0807 11.95 13.72 D. Chis 39230.5610 -0.0036 165 0.1812 12.32 - " 39269.4358 +0.0007 167 0.8995 11.76 - " 39285.3370 +0.0004 169 0.0115 - - 39339.5250 +0.0053 172 0.8006 11.92 - " 39716.4390 -0.0065 199 0.1564 12.25 13.58 " 39719.3925 +0.0022 199 0.3629 12.15 - " 39720.5637 -0.0045 299 0.4447 - - " 39766.5090 +0.0030 202 0.6568 - - " 39770.6275 -0.0011 202 0.9455 11.55 13.65 " 39778.2947 +0.0098 203 0.4816 12.00 13.70 " 39786.5302 0.0000 204 0.0575 12.30 13.67 " 39791.2600 +0.0183 204 0.5882 11.78 - " 39801.2540 +0.0002 205 0.0171 - - " 40014.4550 +0.0025 220 0.0581 11.93 13.64 " 40034.4860 +0.0093 221 0.0043 12.10 13.52 " 40093.3730 +0.0016 225 0.0031 11.97 - " 40104.5775 +0.0161 226 0.2970 - - " 40663.4830 +0.0113 265 0.3786 12.10 - " 40683.4885 -0.0074 266 0.7775 12.26 - " 40732.3770 -0.0014 270 0.1960 11.98 - " 40789.5070 +0.0008 274 0.1908 11.98 - " 40812.4671 -0.0080 275 0.7953 11.98 - " 40822.5000 +0.0127 276 0.4979 12.30 13.48 " 40858.4390 +0.0260 279 0.0101 12.04 13.44 " 40869.6110 +0.0081 279 0.0102 - - " Astronomical Observatory Cluj Rumania DORIN CHIS GHEORGHE CHIS IOAN MIHOC