COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1001 Konkoly Observatory Budapest 1975 May 21 ON THE PERIOD OF THE SECONDARY CYCLE IN XZ CYGNI The amplitude of the RRab Variable XZ Cygni changes periodically between 0.92 and 1.67 magnitudes in B, and between 0.67 and 1.35 in V (Kunchev, 1974). In the Table the moments for the maxima and minima of the amplitude have been compiled from all available data from 1906 to 1973. The majority of the moments were determined on the basis of the original observations. ------------------------------------------------------------- Max.Ampl. (O-C)" Min.Ampl. (O-C)" N Observer J.D. J.D. ------------------------------------------------------------- 2417031: +16d 2417061 +19d -1 Blazko 17087 +13 17118: +18 0 " 17199: +12 2 17255 +10 3 Enebo 19185 +16 36 Blazko 19204 + 5 19228: + 2 37 " 19290 + 6 38 " 19319 + 5 19346 + 5 39 " 20701: + 8 63 Balanovski 20754 + 3 69 Jordan 24378 + 6 24400: + 1 127 Blazko 29439 +10 128 " 24944 - 3 24982 + 8 137 Rybka 25116 - 3 25145 - 1 140 Zaharov 25174 - 3 141 " 25410 + 3 25430 - 4 145 " 25456:: - 8 146 " 25865 - 1 25887 - 7 153 " 26148: - 6 26172: -11 158 " 27697: - 9 185 Blazko 32693 -13 32723:: -10 272 Muller 32788: - 3 273 Klepicova 32814 - 7 32839: - 9 274 Muller, Klepicova 33445 - 8 33471 -10 285 " 33537 - 1 286 " 33560 - 8 33587 - 9 287 Klepicova 34160 -10 297 Muller 34190 -10 34216 -12 298 Muller 34621 - 9 305 Klepicova 34650 -10 39673 -15 306 " 37801: -20 37834:: -15 361 Lange 37861: -18 37893 -13 362 Saharov 38562 - 7 374 Fitch 38683: - 1 376 " 41161 + 6 41199:: +11 419 Bogdanov 91591 +14 425 Kunchev 41571 +15 41599 +14 426 Kunchev 41810 +23 430 Firmanyuk --------------------------------------------------------------- The following elements of the secondary period were determined: Max.Ampl. J.D. = 2 417 072.35 + 57.477d N Min.Ampl. J.D. = 2 917 099.69 + 57.477d N (O - C)" values in the Table were calculated with these elements. [FIGURE 1] The Figure clearly shows the change of the secondary period of XZ Cygni (upper part). The change in the primary period P, obtained on the basis of the collected individual maxima is shown in the lower part of the Figure. The O-C's for the primary period were calculated with the elements: Max. Hel. = 2 417 201.241 + 0.4665878d E (Klepicova, 1959). It is evident that after 1965 the basic period has considerably decreased and the length of the secondary period has increased. Department of Astronomy University of Sofia, Bulgaria P. KUNCHEV Odessa Observatory, USSR References: Klepicova, L.A. 1959, P.Z., 12, No. 3, 164 Kunchev, P. 1979, I.B.V.S. No. 927