COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2799 Konkoly Observatory Budapest 30 September 1985 HU ISSN 0374 - 0676 PHOTOELECTRIC OBSERVATIONS OF TX Cas More than seventy years have elapsed since the eclipsing binary system TX Cas was discovered by Leavitt in 1907. However, the system was only observed visually and photographically until 1981. Recently some photoelectric minima times were given by Fernandes (1982) and Kreiner and Tremko (1984). For this reason the system was observed photoelectrically at Beijing observatory in two intervals, from December 1982 to January 1983 and from October 1984 to January 1985 with the 60 cm reflector by using Stromgren four colour system. In the second interval a total of 367 photoelectric b and y observations were made on 13 nights and combined into the first photoelectric light curves. The moment of the primary minimum was determined using Kwee and Van Woerden's method, and in addition, one time of primary minimum and three times of secondary minimum were determined by using the mean light curve. These moments are given in Table I. Table I J.D.Hel.2440000+ m.e. Min. 5330.020 0.004 I 6003.1882 0.0007 I 6028.067 0.002 II 6030.991 0.002 II 6060.260 0.004 II The star BD + 62deg478 was used as a comparison star and BD + 62deg481 as the check star. All observations were corrected for the differential extinction. Figure 1 gives the b and y light curves of the eclipsing binary TX Cas. Using the photoelectric minima given in Table II, the new ephemeris has been derived by the weighted least squares method as follow: J.D.Hel.Min.I = 2 446 003.1893 + 2.926 835d E +/-.0014 +/-.000 007 [FIGURE 1a] Figure 1.a The y light curve of TX Cas [FIGURE 1b] Figure 1.b The b light curve of TX Cas Table II J.D. Hel. E (O-C) Min. Method Ref. 2400000+ 17551.6380 -9721.0 0.3144d I v (1) 19708.3750 -8984.0 -0.0333 I v (2) 20448.9230 -8731.0 0.0229 I v (3) 29677.2280 -5578.0 -0.0139 I v (4) 30224.5000 -5391.0 -0.0619 I v (5) 30350.4670 -5348.0 0.0508 I v (6) 30792.3120 -5197.0 -0.0578 I pg (7) 33186.4790 -4379.0 -0.0499 I pg (7) 33599.1550 -4238.0 -0.0590 I - (8) 35390.4280 -3626.0 -0.0151 I pg (7) 36596.3150 -3214.0 0.0119 I pg (7) 36824.5410 -3136.0 -0.0560 I pg (7) 37316.3400 -2968.0 0.0330 I pg (7) 37588.3940 -2875.0 -0.1096 I pg (7) 39672.4780 -2163.0 0.0609 I pg (7) 39827.4780 -2110.0 -0.0619 I pg (7) 39915.3330 -2080.0 -0.0122 I pg (7) 40619.2490 -1839.5 -0.0024 II pg (7) 40679.3280 -1819.0 0.0763 I pg (7) 40828.5170 -1768.0 -0.0038 I pg (7) 40831.5280 -1767.0 0.0803 I pg (7) 41166.4600 -1652.5 -0.1114 II pg (7) 41361.2990 -1586.0 0.0924 I pg (7) 41539.5280 -1525.0 -0.2161 I pg (7) 41677.3010 -1478.0 -0.0048 I pg (7) 41990.4730 -1371.0 -0.0052 I pg (7) 42988.5620 -1030.0 0.0297 I pg (7) 43477.2750 -863.0 -0.0404 I pg (7) 43749.4800 -770.0 -0.0320 I pg (7) 44712.4476 -441:0 0.0037 I pe (9) 45056.3510 -323.5 0.0028 II v (10) 45233.4340 -263.0 0.0117 I pe (5) 45280.2710 -247.0 0.0192 I pe (5) 45330.0200 -230.0 0.0118 I pe (11) 45593.4390 -140.0 0.0148 I pe (5) 46003.1882 0.0 0.0057 I pe [11) 46028.0670 8.5 0.0063 II pe (11) 46030.9910 9.5 0.0034 II pe (11) 46060.2600 19.5 0.0040 II pe (11) (1) Pickering; (2) Zinner; (3) McDiarmid; (4) Gaposchkin; (5) Kreiner; (6) GCVS (1948); (7) Ratz; (8) SAC 54; (9) Fernandes; (10) Hubscher, Braune; (11) present paper [FIGURE 2] Figure 2. The O-C diagram of the times of minimum light of TX Cas [triangle] photoelectric, [square] photographic, [dot] visual observations Table II lists the historic minima and their O-C based on the above ephemeris. The O-C diagram (see Figure 2) shows that the period of TX Cas is not subjected to any long-term variation except for some probable short- term fluctuations. A further detailed analysis of these light curves will be given elsewhere. ZHAI DI-SHENG, ZHANG RONG-XIAN, ZHAN JI-TONG, LI CHI-SHENG Beijing Astronomical Observatory Beijing, China References: Fernandes, M., 1982, BAV Mitt., No. 32. Gaposchkin, S., 1953, Ann. Harvard Coll. Obs., 113, 90. [BIBCODE 1953AnHar.113...67G ] Hubscher, J., and Braune, W., 1982, BAV Mitt., No. 34. Kreiner, J.M., and Tremko, J., 1984, IBVS, No. 2254. McDiarmid, R.J., 1915, Astrophys. J., 42,412. [BIBCODE 1915ApJ....42..412M ] Pickering, E.C., 1907, Harvard Circ., No. 127. [BIBCODE 1907HarCi.127....1L ] Ratz, K., 1983, Mitt. Ver. Sterne, 9, 169. Zinner, E., 1913, Astr. Nachr., 195, 453. [BIBCODE 1913AN....195..453Z ]