COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3162 Konkoly Observatory Budapest 22 March 1988 HU ISSN 0374-0676 PHOTOELECTRIC OBSERVATIONS OF THE ECLIPSING BINARY V676 CENTAURI Based on photographic observations, the first light curve of V676 Cen (alpha= 14h34m42s, delta=-38d37.7', 1950.0) was given by Hoffmeister (1956). He determined a difference between minima of the order of 0.1 magnitudes and classified this variable as a W UMa-type system. Besides, Hoffmeister obtained 83 times of minimum which gave the following ephemeris: Min I = J.D. hel 2434425.555 + 0.292397d E (1) So far, no other observations of this star have been published. During 1987 this twelfth magnitude short period eclipsing binary was observed photoelectrically in the UBV system using the 76 cm and the 154 cm telescopes of El Leoncito (San Juan, Argentina) and Bosque Alegre (Cordoba, Argentina) stations, respectively. At El Leoncito an RCA 34031 (A) photomultiplier refrigerated by Peltier effect and photon-counting electronics were used. The observations at Bosque Alegre were performed by means of an RCA 1P21 photomultiplier refrigerated with dry ice. Standard UBV filters were employed [FIGURE 1] Table I. Photoelectric times of minimum light of V676 Centauri JD hel. Min 2440000 E O-C II 6965.6195 -20.5 -0.00171 II 6965.6199 -20.5 -0.00131 II 6965.6167 -20.5 -0.00151 I 6971.6167 0.0 0.00149 I 6971.6167 0.0 0.00149 I 6971.6155 0.0 0.00029 II 6973.5174 6.5 0.00165 II 6973.5163 6.5 0.00055 II 6973.5184 6.5 0.00265 II 6975.5618 13.5 -0.00068 II 6975.5607 13.5 -0.00178 II 6975.5617 13.5 -0.00078 II 6978.4869 23.5 0.00052 II 6978.4867 23.5 0.00032 II 6978.4858 23.5 -0.00058 I 7007.5860 123.0 0.00111 I 7007.5814 123.0 0.00221 II 7008.6001 126.5 -0.00246 II 7008.6011 126.5 -0.00146 in both cases. The measurements were made differentially with respect to the comparison star HD 128488. All the observations were corrected by first and second order differential extinction using mean coefficients for both observatories. A total of 1326 UBV observations were derived and from them 19 new times of minima were calculated. These times of minima were used to deduce the following linear least squares ephemeris: Min I = Hel. J.D. 2446971.61521 + 0.2923901d E (2) +/-0.00034 +/-0.0000057 The photoelectric minima together with the epoch number and O-C residuals calculated from the ephemeris given in equation (2), are listed in Table I. As shown in the table, the difference between the observed minima and those calculated from ephemeris (2) yield very small randomly distributed O-C residuals, all being smaller than 0.003 day. Although the coverage of the photoelectric light curve (Figure 1) is not complete, there is no doubt that we are dealing with a close (contact) system. The continuous light variation due to proximity and reflection effects of the components outside eclipses is easily recognized. Besides the difference in brightness during the primary and the secondary minima is only about 0.15 m. The observations of this variable will be continued during the next observing seasons to complete the light curves and tp analyze them by means of modern synthetic computational methods. For assistance during observations we thank Messrs. J. Laborde, J.R. Puerta and J. Ahumada. Also we express our gratefulness to the Director of Felix Aguilar Observatory for the observing time. This work was partially supported by the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) of Argentina. M. GOMEZ, E. LAPASSET Observatorio Astronomico, Universidad Nacional de Cordoba Laprida 854, 5000 Cordoba, Argentina Reference: Hoffmeister C., 1956, Veroffentlichungen der Sternwarte zu Sonneberg, Band 3, Heft 1, p. 43. [BIBCODE 1956VeSon...3....1H ]