COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1813 Konkoly Observatory Budapest 1980 July 7 PHOTOELECTRIC OBSERVATIONS OF SYMBIOTIC STARS The brightness variability is one of the criteria for the symbiotic stars. Their brightness can vary with an amplitude up to 3 magnitudes and a period of several years. The light variations are irregular and the features of the lightcurves can vary from time to time. A definite period can be found for many stars, but for some of these objects it is possible to assume an approximate mean period only; superimposed on this periodicity there is a complex of small simultaneous flares, which give rise to the irregular shape of the lightcurves. From the list of Boyarchuk (1969) some symbiotic objects were chosen to fill the gaps in time among the stars of the main programs, being of interest to make a photoelectric monitoring of their variability. All the observations were made by an analogical B-V photo- meter employing an EMI 9502 photomultiplier, the filters Schott GG14 + GG13 (2mm) for the V light, and Schott BG72 + GG13 (2mm) for the B one, with the Teramo Observatory's 40 cm refractor at Collurania. In Table I are reported the comparison and check stars used for every symbiotic object, the coordinates and the magnitudes V and B-V, as determined by comparison with several standard stars in more nights of good quality. In Table II the observations are listed: each value is the mean of several points and the mean nightly errors are also reported. It should be noted that the reported values of the magnitudes are relative to the response curve of the used photometer, as in all cases of broad-band observations of stars having emission lines in their spectra. The following stars have been observed: Table I Comparison and check stars Symbiotic Comparison and R.A. Decl. V m.e. B-V m.e. stars check stars (1975) (1975) RW Hya 1-CPD -24deg5104 =CoD 10984 13h33m42s 25deg10.6arcmin 9.00 0.01 0.54 0.02 AG Dra 1-BD +67deg925 16 05 14 +66 51.2 9.86 0.01 0.55 0.01 FR Sct 1-BD -12deg5023 18 21 48 -12 39.3 10.07 0.01 1.48 0.02 2-BD -12deg5028 18 22 11 -12 40.4 9.997 0.002 0.98 0.04 BF Cyg 1-Anon. 19 21 22 +29 44.0 11.31 0.02 0.51 0.02 2-Anon, 19 23 26 +29 37.2 11.10 0.02 0.32 0.01 MHalpha 80-5 1-Anon. 19 45 22 +18 30.4 10.83 0.01 0.41 0.02 AG Peg 1-BD +11deg4677 21 50 29 +11 55.1 7.609 0.004 0.167 0.004 2-BD +11deg4681 21 51 12 +12 25.7 8.178 0.001 1.011 0.004 Table II Photometry of symbiotic stars Star Jul.Day V m.e. B-V m.e. 2440000.+ RW Hya 702.486 8.80 0.01 1.56 0.01 704.453 8.80 0.01 1.51 0.01 720.404 8.83 0.01 731.356 8.82 0.01 AG Dra 686.441 9.85 0.01 1.38 0.02 689.340 9.84 0.01 1.39 0.02 701.311 9.87 0.01 702.434 9.857 0.004 1.45 0.01 704.391 9.84 0.01 1.47 0.01 710.483 9.848 0.003 1.37 0.02 715.467 9.86 0.01 1.43 0.02 720.431 9.85 0.01 731.378 9.85 0.01 741.374 9.849 0.002 1.41 0.01 748.376 9.82 0.01 764.364 9.82 0.02 1.43 0.02 767.393 9.83 0.02 1.45 0.05 773.375 9.810 0.005 1.37 0.01 800.377 9.78 0.01 824.328 9.74 0.01 1.32 0.02 837.421 9.76 0.01 FR Sct 741.541 10.21 0.01 2.14 0.02 748.520 10.16 0.02 765.489 10.20 0.01 772.448 10.26 0.01 798.366 10.34 0.01 2.57 0.04 802.363 10.20 0.01 824.354 10.09 0.01 HF Cyg 769.389 11.12 0.01 0.80 0.01 775.382 11.22 0.02 0.73 0.01 798.396 11.42 0.02 0.81 0.03 809.361 11.44 0.02 833.373 11.34 0.03 865.311 11.40 0.02 MHalpha80-5 770.380 10.619 0.005 0.43 0.01 Table II (cont. ) Star Jul.Day V m.e. B-V m.e. 2440000.+ AG Peg 834.410 8.30 0.01 865.345 8.241 0.005 866.477 8.252 0.004 0.76 0.01 RW Hya = HD 117970. Extended photometric observations are not reported for this star, which has a spectroscopic period of about 376 days. AG Dra = BD +67deg922. In 1970 its behaviour is the same as in the years 1962-67 with an amplitude of 0m12 and 0m15 for U and B light, respectively. FR Sct. In 1970 its mean magnitude is greater (10m21+-0m03) than previously reported (11m7 to 12m5). It is much more likely to be a VV Cep star than a symbiotic one. BF Cyg. It is a typical symbiotic star (Z And type) in which the quasi-periodic variations are smaller and the non-periodic part is very important. MHalpha 80-5. The star may be symbiotic. The V magnitude in 1970 is greater than that previously known at the maximum. AG Peg = HD 207757 = BD +11deg4673. The star may be regarded as a binary system involving an M giant, a hot emission object, gaseous streams and an enveloping nebulosity. The period is about 820 days. R. BURCHI Teramo - Collurania Observatory References: 1. Boyarchuk, A.A., 1968, Non Periodic Phenomena in Variable [BIBCODE 1969CoKon..65..395B ] Stars, I.A.U. Colloquium, Budapest, p.395 [CoKon No. 65] 2. Cowley, A., Stencel, R., 1973, Astrophys.J., 184, 687 [BIBCODE 1973ApJ...184..687C ] 3. Hutchings, J.B., Cowley, A.P., Redman, R.O., 1975, Astrophys. J., 201, 404 [BIBCODE 1975ApJ...201..404H ]