COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 2994 Konkoly Observatory Budapest 10 March 1987 HU ISSN 0374 - 0676 uvby beta PHOTOMETRY OF V1719 Cyg uvby photoelectric photometry of the pulsating variable V1719 Cyg was carried out at Abastumani Astrophysical Observatory during three nights, 10- 11, 11-12, 12-13 September, 1986 with the 125 cm automatic reflector. Measurements were made relative to the star HD 200739. Crawford's primary standards were found to be too bright for our apparatus; besides, they are considerably far from the comparison star. So HD 200739 was reduced to HD 201319. Photometric characteristics for the latter were taken from the catalogue of Perry and Johnson (1982). The results for the comparison star are as follows: y = 8.282 +- 0.007, b-y = 0.096 +- 0.005, m_1 = 0.227 +- 0.010, c_1 = 1.009 +- 0.014, beta = 2.854 +- 0.016 (the r.m.s. errors are obtained for a series of 20 observations). Such a high value of the m_1 index for HD 200739 was not a surprise as it is a metallic line star (Bertaud, 1960). The technique of observing the RR Lyrae stars with our telescope was previously discussed in detail (Alania and Abuladze, 1986). Altogether 220 light estimations are obtained for V1719 in each colour of the uvby beta system. They are very well distributed in phase. By averaging the observed values close in phase the normal curves v, b-y, m_1, c_1 and beta were drawn, Then, according to Crawford's method (1975, 1979) they were corrected for the effect of the interstellar light absorption. On the average E(b-y) = 0.042 was obtained. Phases were calculated according to Poretti's (1984) elements Max.Hel. = 2444212.145 + 0d.267298.E According to our observations O-C=-0p.07. b-y and c_1 corrected for the interstellar absorption, were plotted on Relyea and Kurucz's (1978) theoretical diagrams for b-y and c_1 to determine the effective temperatures and gravity on the stellar surface for the solar content. Calculations were carried out for each phase of the normal curves. Figure 1 shows the variations of all the photometric characteristics for V1719 Cyg during a cycle. It is known that RRc stars are characterised by a certain structure at their maxima on the light curves. This feature was not observed for the star in question. A mean value of m_1 over the cycle is 0.197, which according to the relation (Butler, 1975) [Fe/H] = 15.87(m_1)_0 - 2.86 gives +0.3 for [Fe/H]. [FIGURE 1] In addition, m_1 somewhat decreases near the maximum light of V1719 Cyg. Table I contains the extreme values of V=y, b-y, c_1, beta, T_eff and lg g. Table I Parameters Max. Min. Amplitude y 7.63 7.96 0.33 b-y 0.172 0.253 0.081 c_1 0.935 0.724 0.211 beta 2.755 2.685 0.070 T_eff 7300 6700 600 lg g 3.40 3.20 0.20 The observational material and discussion will be published elsewhere. I.PH. ALANIA Abastumani Astrophysical Observatory, Academy of Sciences of the Georgian SSR, U.S.S.R. References: Alania, I.Ph. and Abuladze, O.P., 1986, Bull. Abastumani Astrophys. Obs., 61, 3 [BIBCODE 1986AbaOB..61....3A ] Bertaud, Ch., 1960, J. Obs. 43, 129. [BIBCODE 1960JO.....43..129B ] Butler, D., 1975, Astrophys. J. 200, 68. [BIBCODE 1975ApJ...200...68B ] Crawford, D.L., 1975, Astron. J. 80, 955 [BIBCODE 1975AJ.....80..955C ] Crawford, D.L., 1979, Astron. J. 84, 1858 [BIBCODE 1979AJ.....84.1858C ] Perry, C.L. and Johnson, L., 1982, Astrophys. J. Suppl. 50, 451. [BIBCODE 1982ApJS...50..451P ] Poretti, E., 1984, Astron. Astrophys. Suppl. 57, 435. [BIBCODE 1984A&AS...57..435P ] Relyea, L.J. and Kurucz, R.L., 1978, Astrophys. J. Suppl. 37, 45. [BIBCODE 1978ApJS...37...45R ]