COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2749 Konkoly Observatory Budapest 19 June 1985 HU ISSN 0374 - 0676 NEW VARIABLE STARS FOUND IN SOUTHERN OPEN CLUSTERS In this note we report the variability detected photoelectrically in sixteen stars located in the vicinity of the southern open clusters NGC 2323, NGC 2567, IC 2395, NGC 5460, and NGC 5662. We are studying all these clusters using new photometric and spectroscopic material obtained at Cerro Tololo (CTIO) and Las Campanas (LCO) observatories. The project, initiated a couple of years ago, consists in obtaining UBV photometry and classification of spectra as basic data to investigate the fundamental properties of the selected clusters. A total of 1040 stars in the cluster fields have been measured photoelectrically during various observing runs in 1984-1985, using the 60 cm telescope of the David Dunlap Observatory at LCO, and the CTIO 91 cm and 1 m telescopes. Several red stars in the cluster fields have also been observed in the DDO intermediate-band system (McClure and van den Bergh 1968; McClure 1976) and the CMT1T2 broad-band system (Canterna 1976). A large number of standard stars, taken from the lists of Cousins (1973, 1974), McClure (1976), and Canterna (1976), were observed each night for conversion to the standard UBV, DDO, and Washington systems, respectively. Pulse-counting electronics was used for all measurements. Photometric errors are similar to those quoted in previous papers (e.g., Claria and Rosenzweig 1978; Claria and Lapasset 1983). The mean internal error is about 0.02mag, a value which is practically independent of the V-magnitude and the telescope used. We have considered a star to be photometric variable when its individual V measures during different nights displayed variations greater than five times the mean internal error, i.e., DeltaV>=0.1mag. Among the new photometric variables detected there are nine which are members or probable members of the clusters (Claria and Lapasset 1985), while the other seven are almost certainly non- member field stars. Four of the new variables exhibit DeltaV variations greater than 0.20mag, while the other twelve stars have DeltaV variations in the interval 0.10mag<= V<= 0.20mag. The individual UBV observations of the new variables are listed in Table I. The references for star identifications are given at the head of each section of the table. Column (2) of Table I lists the heliocentric Julian Date. The magnitude and colours in the UBV system are given in columns (3)-(5), while column (6) gives the spectral type as estimated from the UBV colours. The last column of Table I indicates if the star is considered to be cluster member (m), a probable member (pm), or a non-member (nm) field star. Finding charts for the variable stars are shown in Figures 1 to 4. The new variables found in NGC 2567 are shown in the finding chart published by Lindoff (1968). Table I: Individual UBV observations of new variable stars found in southern open clusters. STAR HJD V B-V U-B Sp. Type Membership 2440000 + NGC 2323 (Claria and Lapasset 1985) 58 6111.6149 12.541 0.279 0.281 A1 m 61112.5583 12.432 0.379 0.279 6167.5106 12.475 0.349 0.302 6168.4912 12.480 0.333 0.276 100 6111.6499 12.826 0.674 0.179 F8 pm 6112.5121 12.926 0.603 0.139 6167.5167 12.891 0.610 0.178 6168.4937 12.868 0.640 0.150 160 6111.6880 12.561 0.616 0.124 F8 nm 6112.6138 12.557 0.522 0.187 6167.5614 12.453 0.594 0.052 6168.5420 12.524 0.577 0.121 NGC 2567 (Lindoff 1968) 19 6112.6995 13.111 0.396 0.091 A7 pm 6113.6127 13.310 0.275 0.173 6115.5762 13.240 0.365 0.122 6168.5774 13.305 0.316 0.124 35 6112.7591 12.947 0.468 0.091 F6 nm 6113.6760 12.900 0.525 -0.033 6115.7382 13.030 0.451 0.000 40 6112.7669 13.841 0.264 0.176 A7 m 6113.6760 13.730 0.336 0.195 6114.6406 13.782 0.304 0.147 58 6112.6825 13.057 0.257 0.085 A5 m 6113.6026 12.912 0.352 0.100 6115.5584 12.930 0.266 0.123 6168.5295 13.016 0.251 0.132 Table I (continued) STAR HJD V B-V U-B Sp. Type Membership 2440000+ IC 2395 (Claria and Lapasset 1985) 169 5762.7436 11.811 0.568 0.088 F8 nm 5763.6896 11.919 0.449 0.058 5764.7196 11.759 0.558 0.051 215 5762.6901 13.575 0.698 0.129 G0 pm 5766.5873 13.688 0.665 0.124 5767.6165 13.632 0.682 0.127 220 5781.6215 13.014 0.853 0.628 K1 nm 5782.6795 13.331 0.580 0.583 NGC 5460 (Claria and Lapasset 1985) 330 5760.8987 13.056 0.625 0.079 G0 pm 5765.8063 13.175 0.599 0.041 5768.7884 13.178 0.570 0.075 337 5764.7675 12.935 0.384 0.038 F6 pm 5767.7932 12.787 0.452 -0.002 5765.8055 12.785 0.494 0.002 366 5761.8073 12.449 1.200 0.975 K3? nm 5762.8267 12.048 0.782 0.289 5767.8523 12.537 1.131 1.079 375 5764.8179 13.006 0.426 0.063 F7 pm 5765.8722 12.846 0.549 0.099 5767.7982 12.912 0.527 0.018 NGC 5662 (Claria and Lapasset 1985) 17 6112.8627 11.476 0.362 0.088 F2 nm 6113.7821 11.364 0.415 0.214 6118.7769 11.465 0.378 0.160 166 6111.8559 12.775 0.582 0.360 F8? nm 6113.8883 12.713 0.606 0.440 6118.8843 12.664 0.686 0.348 6167.8197 12.703 0.601 0.403 [FIGURE 1] Figure 1: Finding chart for the variables found in NGC 2323. [FIGURE 2] Figure 2: Finding chart for the variables found in IC 2395. [FIGURE 3] Figure 3: Finding chart for the variables found in NGC 5460. [FIGURE 4] Figure 4: Finding chart for the variables found in NGC 5662. We are very grateful to staff members, night assistants, and visitors' support both of CTIO and LCO for the observing time and their kind hospitality. This work was partially supported by CONICET and CONICOR of Argentina. E. LAPASSET Observatorio Astronomico, Universidad Nacional de Cordoba, Argentina Visiting Astronomer, University of Toronto (David Dunlap Observatory) 24 inch telescope at Las Campanas Observatory. J. J. CLARIA Observatorio Astronomico, Universidad Nacional de Cordoba, Argentina Visiting Astronomer, Cerro Tololo Inter-American Observatory, operated by the Association for Research in Astronomy, Inc., under contract with the National Science Foundation References: Canterna R. 1976, Astron. J. 81, 228. [BIBCODE 1976AJ.....81..228C ] Claria, J.J., and Rosenzweig P. 1978, Astron. J. 83, 278. [BIBCODE 1978AJ.....83..278C ] Claria, J.J., and Lapasset, E. 1983, J.Astrophys. and Astron. 4, 117. [BIBCODE 1983JApA....4..117C ] Claria, J.J., and Lapasset, E. 1985 in preparation. Cousins, A.W.J. 1973, Mem.Roy.Astron.Soc. 77, 223. [BIBCODE 1973MmRAS..77..223C ] Cousins, A.W.J. 1974, Mon.Not.Astron.Soc.So. Africa 33, 149. [BIBCODE 1974MNSSA..33..149C ] Lindoff, U. 1968, Arkiv Astron. 4, 587. [BIBCODE 1968ArA.....4..587L ] McClure, R.D. 1976, Astron. J. 81, 182. [BIBCODE 1976AJ.....81..182M ] McClure, R.D., and van den Bergh, S. 1968, Astron. J. 73, 313. [BIBCODE 1968AJ.....73..313M ]