COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1982 Konkoly Observatory Budapest 1981 June 25 HU ISSN 0374-0676 PHOTOELECTRIC OBSERVATIONS OF THE LOW-AMPLITUDE CEPHEID V1726 Cyg V1726 Cyg (=BD + 48d3398=SAO 050939=SVS 2299) was discovered and classified as a cepheid variable with low amplitude and sinusoidal light curve in the course of a detailed investigation of the open cluster M39 by one of the authors (I.P., 1979). Our previous photographic photometry revealed the basic properties of the variable V1726 Cyg, i.e. the form of the light curve, period, amplitude and colour indices. It, however, became clear that more precise photometry was desirable in view of the possible membership of the cepheid V1726 Cyg to an anonymous open cluster (I.P., 1979). The cepheid V1726 Cyg was observed photoelectrically using the 0.6 m Zeiss reflector equipped with an uncooled photomultiplier EMI 6256s and filter combination reasonable close to the standard UBV system at the Crimean station of the Sternberg Astronomical Institute. Several observations were made with an analogous reflector but with another photometer at Maydanak, the high-mountain expedition of the Tashkent Astronomical Institute. All the observations were converted to the UBV system. The comparison star was the standard star No 9 = BD + 47d3439 (Johnson, 1953) and it was monitored both before and after every observation of the cepheid. The results of our BV photoelectric photometry of the cepheid V1726 Cyg are listed in Table I. Observations made at zenith distances greater than 51d are marked by colon. In Figure 1 the composite V and (B-V) curves versus phase are plotted according to the revised elements, Max_v JD hel = 2444105.39 + 4.2359d*E Table I. B,V observations of the cepheid V1726 Cyg JD hel V B-V JD hel V B-V (2444000+) (2444000+) 021.507 8.960 0.904 032.519 8.928 0.885 022.382 9.049 0.952: 033.340 8.885 0.846: 022.525 9.050 0.936 033.473 8.877 0.872 023.387 9.022 0.931: 034.368 8.975 0.941: 023.517 9.016 0.909 034.515 8.997 0.925 024.357 8.892 0.893: 035.430 9.063 0.952 024.511 8.895 0.849 035.516 9.059 0.942 025.359 8.909 0.889: 037.441 8.888 0.857 027.484 9.023 0.934 037.523 8.873 0.865 027.492 9.022 0.920 039.441 9.060 0.944 028.364 8.923 0.879: 039.526 9.061 0.957 028.515 8.924 0.876 457.397 8.894 0.887 030.368 8.987 0.927: 461.173 8.859 0.865 030.521 9.032 0.930 464.155 8.992 0.912 031.355 9.060 0.938: 464.161 8.989 0.929 031.518 9.054 0.956 465.157 8.869 0.865 032.469 8.947 0.892 466.160 8.900 0.902 [FIGURE 1] Figure 1: Composite V and (B-V) curves of V1726 Cyg. Dots - Crimean observations, dots in bracket - Crimean observations at z > 51deg, triangles - Maydanak observations. In addition we performed a Fourier analysis for the composite light and colour curves (the solid curves in Figure 1), using the algorithm of Schaltenbrand and Tammann (1971). The extreme and intensity averaged values of the cepheid V1726 Cyg magnitudes in V,B and (B-V) are shown in Table II. The (U-B) variations are marginal (probably less than 0.04m) and as we failed to match the two different sets of observations in U-light it is not reasonable to present these observations. Table II. The light curve parameters of V1726 Cyg Period = 4.2359d Log P = 0.6269 V_max = 8.872 V_min = 9.061 Delta V = 0.189 B_max =9.736 B_min =10.007 Delta B = 0.271 = 8.967 = 9.872 = 0.908 We would like to thank Dr. Z. Kadla for constant interest and encouragement. I. PLATAIS S. SHUGAROV Main Astronomical Observatory Sternberg State Astronomical Pulkovo, Leningrad, U.S.S.R. Institute, Moscow, U.S.S.R. References: Johnson, H.L., 1953, Astrophys. J., 117, 353 [BIBCODE 1953ApJ...117..353J ] Platais, I., 1979, Astron. Circ., No. 1049, 4 [BIBCODE 1979ATsir1049....4P ] Schaltenbrand, R., Tammann, G.A., 1971, Astr. Astrophys. Suppl., 4, 265 [BIBCODE 1971A&AS....4..265S ]