COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 386 Konkoly Observatory Budapest 1969 October 6 PV CASSIOPEIAE - AN ECLIPSING BINARY WITH ECCENTRIC ORBIT? As a part of the joint photoelectric program on eclipsing binaries of the Observatories Izmir and Nurnberg 4 photoelectric minima of this star were obtained with the 48 cm Cassegrain telescope at the University - Observatory of Izmir during the period 1968 September to 1969 September, They all show very big O-C's against the elements given in SAC 40 (1969) (+0.061d, +0.060, +0.060, +0.062). 2 photoelectric minima, obtained by GEYER (1967 November and December), show the following O-C's against the same elements: +0.027d, +0.056! The difference in epochs between the 2 minima of GEYER is uneven, while the differences in epochs between the 4 minima from Izmir and the second minima of GEYER are even! GEYER has expressed the suspicion, that the uneven minima were not situated symmetrically between the even minima, consequently the star has an eccentric orbit and the period must be doubled. Part 1. For all observed minima O-C's were calculated against elements with a mean period and the earliest observed (normal-) minimum (T_0). For the time interval JD 2415 600 to JD 2436 900 I found, with friendly help of Mr. HUTH, Sonneberg - Observatory, 130 photographic minima. In the last years 8 photoelectric minima (by GEYER and the Izmir Observatory) were obtained. From 3 photographic minima I derived T_0 = JD 2415 764.553 The latest observed photoelectric minima is T_n = JD 2440 479.474 The number of epochs between T_n and T_0 is DeltaE = 28 238 The mean period: P = (T_n-T_0): DeltaE = 0.8752362d The O-C's were calculated with the elements: Min JD 2415 764.553 + 0.8752362 . E In Table 1 the mean values for O-C_I (even E) and O-C_II (uneven E) are given, each for a period of 2000 or 3000 epochs; n is the number of minima, from which O-C was calculated. Table 1 E n_I n_II (O-C)_I (O-C)_II Delta(O-C)_II-I 0 - 3000 8 8 -0.025d -0.001d +0.024d pg +/-13 +/-8 3000 - 6000 4 7 -0.008 +0.027 +0.035 " +/-5 +/-14 9000 - 12000 10 5 -0.002 +0.014 +0.016 " /-+13 +/-10 12000- 14000 11 8 -0.011 +0.028 -0.039 " +/-15 +/-15 14000- 16000 17 9 -0.006 +0.001 +0.007 " +/-7 +/-6 16000- 18000 8 6 -0.005 +0.019 +0.024 " +/-9 +/-7 18000- 20000 8 9 -0.005 -0.004 +0.001 " +/-10 +/-10 20000- 22500 8 6 +0.003 -0.007 -0.010 " +/-7 +/-10 24000 - 28500 5 3 +0.0005 -0.0280 -0.0385 pe +/-4 +/-5 The O-C_II's (uneven E) are systematically greater than those with even E (O-C_I) for the period E=0 to E=1700. At E = 19000 the O-C's are equal, thereafter the O-C_II's are smaller than O-C_I. The mean errors of the O-C's are large, but there are some real effects: 1.) PV Cas has an eccentric orbit, and 2.) perhaps an apsidal motion with a period longer than about 120 years. 3.) The period must be doubled. 4.) At present time we have Min I - Min II = 0.5 . P + 0.029d. Part 2. For minima I new light-elements were calculated by the method of least squares. From photographic estimates 4 normal - minima were derived (each from 5 to 8 minimas published by BUSCH, FILIN, GEYER, PEROVA and STROHMEIER. 1 photoelectric minimum of GEYER was used and 4 photoelectric minima from Izmir (observed by GULMEN, GUDUR, IBANOGLU and KURUTAC) were combined to 2 normal- minima. Table 2 gives the observed Minima, O-C_1 (elements of SAC 40, 1969), O-C_2 (new elements). Table 2 Min. (JD) O-C_1 O-C_2 24 28 796.814 pg -0.015d 0.000d 31 018.164 " -0.001 -0.001 32 439.548 " +0.008 -0.001 34 608.391 " +0.028 +0.005 39 835.2976 pe +0.055 -0.0022 40 129.3805 " +0.061 +0.0011 40 479.4735 " +0.061 -0.0006 C_1: (SAC 40) Min JD 2428 126.402+ 0.875231d E 2P = 1.750462 C_2: (POHL) Min JD 2428 796.8142+ 1.75047346d E +/-17 +/-38 Min I - Min II = 0.5 P + 0.029d = 0.516 P E. POHL Nurnberg Observatory 85 Nurnberg, Lutzowstr. 10 Germany