COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 883 Konkoly Observatory Budapest 1974 April 17 PHOTOELECTRIC PHOTOMETRY OF THE ECLIPSING BINARIES RZ Cas AND AR Lac For the past two seasons this investigator has been engaged in photometric studies of the eclipsing binaries RZ Cas and AR Lac. All observations have been made with the 18" Cassegrain reflector and photoelectric photometer of the Kutztown State College Observatory. Thus far about 1400 observations in U,B,V have been obtained on RZ Cas and about 1650 on AR Lacertae. Detailed studies of both RZ Cas and AR Lac will be published after these investigations have been completed. RZ Cassiopeiae is a 6th magnitude eclipsing binary of the semi-detached type, the components of which are of spectral types A2V and K0IV. As a comparison the A2 star HR 791, a star previously used by several investigators, has been chosen. This investigation yields values of V = 5.91, B-V = +0.11, and U-B = +0.12 for HR 791. RZ Cas has long been known to have a variable period, and a vast number of times of minimum light, chiefly visual, have been obtained over the years. The following table lists the recent photoelectric times of minimum light which have been obtained for this star including five which have been obtained by this investigator. Hel. JD E O - C Ref. 2439025.3008 0 -0.0017d IBVS No.148 32.4730 6 -0.0010 148 62.3562 31 +0.0010 148 68.3316 36 +0.0001 148 784.2876 635 +0.0015 322 877.514 713 -0.0016 285 40054.4168 861 +0.0042 456 127.3742 922 +0.0044 456 274.3375 1045 -0.0011 501 519.3669 1250 +0.0021 530 746.4607 1440 -0.0016 530 758.4125 1450 -0.0023 530 819.3702 1501 -0.0023 530 1162.406 1788 -0.0032 647 1199.4583 1819 -0.0037 647 1708.6392 2245 +0.0008 - 1726.5680 2260 +0.0008 - 1732.5442 2265 +0.0008 - 1990.7188 2481 +0.0014 - 2094.7056 2568 +0.0015 - 883/2 A least squares solution with all data given equal weight yields the following ephemeris: Hel. Min I = JD 2439025.3025 + 1.1952499d x E +/- 6 +/- 4 p.e. For RZ Cas the following magnitudes and colors have been obtained. V B-V U-B maximum 6.18 +0.14 +0.08 primary 7.72 +0.22 +0.14 secondary 6.26 +0.12 +0.07 The depths of the minima are as follows: V B U minimum I 1.54m 1.62m 1.68m minimum II 0.08 0.06 0.05 Although the primary minimum of RZ Cas has been suspected of being a complete occultation, these data prove that the eclipses cannot be complete. The values of B-V and U-B at primary minimum are completely incompatible with those of a K-type subgiant. AR Lacertae is a 5th magnitude eclipsing binary system, consisting of a G2 subgiant and a K0 subgiant. As a comparison star the investigator has used the F8 star HD 210731, whose magnitudes and colors he has determined as V = 7.37, B - V = +0.57 and U - B = +0.07. AR Lacertae is also known to have a variable period. The following table lists the recent photoelectric times of minimum light which have been obtained for this star including five which have been obtained by this investigator. Hel. JD E O - C Ref. 2439376.4926 0 -0.0029d IBVS No. 201 383.4386 3.5 +0.0019 201 976.268 252 +0.0065 456 2440932.3168 784.5 +0.0020 817 1592.7219 1117.5 +0.0019 - 1593.7124 1118 +0.0008 - 1604.6224 1123.5 +0.0032 - 1936.8022 1291 -0.0028 - 1938.7874 1292 -0.0008 - A least squares solution, in which the time of the primary minima were given double the weight of the shallower secondaries, yielded the following ephemeris: Hel Min. I = JD 2439376.4955 + 1.9831987d x E +/- 15 +/- 15 p.e. One thing that is apparent from the residuals is that those for primary minimum tend to be negative while those for secondary tend to be positive. Excluding the evidently imprecise results for JD 2439876, the times of primary minimum have an average residual of -0.0014d while the times of secondary have an average of +0.0022d. This difference of 0.0036d implies that secondary minimum occurs 5.2 minutes after 0.50 phase or at a phase of 0.5018. A small orbital eccentricity is indicated. For AR Lacertae the following magnitudes and colors have been obtained. V B-V U-B maximum 6.11 +0.72 +0.26 primary 6.77 +0.83 +0.50 secondary 6.43 +0.71 +0.22 The depths of the minima are as follows: V B-V U-B minimum I 0.66m 0.77m 1.01m minimum II 0.32 0.31 0.27 AR Lacertae has complete eclipses, the primary being an occultation and the secondary a transit. The primary eclipse is total for 129 minutes and during that time only the K0 component is visible. The values of B-V and U-B obtained for primary minimum are normal for a star of this type. AR Lacertae has recently been discovered to be a source of radio outbursts. The observations of this investigator, however, do not indicate substantial short-term light fluctuations. CARLSON R. CHAMBLISS Kutztown Sate College Kutztown, Penna., USA April 5, 1974