COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3054 Konkoly Observatory Budapest 29 July 1987 HU ISSN 0374-0676 A POSSIBLE NEW BINARY STAR IN SAGITTARIUS In a recent paper, Campos and Sanchez (1987) reported the variability of six new variable stars in the constellation of Sagittarius. These discoveries were carried out in photographic plates dating from 1942 to 1954, but their report did not include the type of variability of each star. The present paper reports the variability of one of these stars, ("B"), with the following coordinates; RA = 18h40m26s, DEC = -29d6'6" (2000), based on the same photographic material utilized by Campos and Sanchez (1987). The variability of the star is striking since it appeared in some plates with equal brightness when compared to the same standard plate (BM 111) used by Campos and Sanchez (1987) and it did not appear in some other plates. Since the limit of detectability on the 60 min exposed plates is of about 14 mag, it was safely concluded that at certain times the star was fainter than this magnitude. The entire collection of plates with exposures times of 50 and 60 minutes was compared with respect to the BM 111 plate and the results are presented in Table I and shown schematically in Figure 1. From the light curve of the "B" star it can be concluded that it might be an eclipsing binary with an amplitude of variation larger than 2 magnitudes and a period of about seven years. Recent observations, at the 1.5 m telescope of San Pedro Martir Observatory carried out with the Danish photometer, on the night of June 21-22, 1987 indicate that the V magnitude of this star in that time was of 12.54 mag. Of course, the material available does not exclude another type of variability, such as a flare star or a nova-like object, particularly because [FIGURE 1] Figure 1 Light curve of the suspected variable star. When the star was visible a visual magnitude of 12.5 was assumed. At other times it was fainter than 14 mag., the detection limit. To convert the x axis into years, add 1900. The continuous line is an eye-ball free-hand fit through the points. Table I. Log of observations of the suspected new variable star. In the column denoted by E, Y indicates that the star was visible, N that was not detected. DATE PLATE EXPOSURE TIME (M) E 1942 Apr. 9-10 BM 111 60 Y 1946 Apr. 1-2 1127 60 Y 3-4 1134 60 Y 5-6 1143 60 Y 6-7 1146 60 Y 7-8 1149 60 Y May 30-1 1151 60 N Jun. 22-23 1157 50 N 25-26 1158 60 N 25-26 1159 50 N 25-26 1160 50 N 25-26 1161 50 N 25-26 1162 50 N 25-26 1163 50 N 26-27 1165 50 N 26-27 1166 50 N 26-27 1167 50 N 26-27 1168 50 N 27-28 1169 50 N 27-28 1170 50 N 27-28 1171 50 N 27-28 1172 50 N 27-28 1175 50 N Jul. 26-27 1177 60 N 27-28 1179 60 N Aug. 29-30 1191 60 N 1947 Mar. 26-27 1318 60 N Apr. 16-17 1319 60 N 21-22 1321 60 N Jun. 14-15 1326 60 N Jul. 9-10 1331 60 N 15-16 1332 60 N Sep. 16-17 1344 60 Y 1950 Aug. 6-7 1433 50 N 9-10 1435 60 N 10-11 1436 50 N 11-12 1437 60 N 1951 Apr. 10-11 1464 60 N 12-13 1465 50 N 17-18 1466 60 Y May 3-4 1469 60 N 6-7 1471 60 N 7-8 1472 50 N Jun. 7-8 1477 50 N 7-8 1472 50 N Aug. 6-7 1489 60 Y 27-28 1439 60 Y Sept. 25-26 1498 60 Y 27-28 1499 60 Y 1953 Mar. 11-12 1664 60 Y 16-17 1666 60 Y 17-18 1667 60 Y 19-20 1668 60 Y 23-24 1669 60 Y 25-26 1671 60 Y Apr. 23-24 1679 60 Y May. 18-19 1683 60 N the existence of only one isolated visible point in April, 1951, surrounded by five undetectable points all taken in about the same epoch. Therefore, more observations are needed for the accurate determination of the real nature of this star. We would like to thank C. Chavarria, M.A. Hobart and A. Arellano for fruitful discussions. Drawings were made by G. Ceron, typing by B. Aguilar and proofreading by J.A. Miller. JOSE H. PENA, JOAQUIN CAMPOS and ROSARIO PENICHE Instituto Nacional de Astrofisica, Optica y Electronica Reference: Campos, J., and Sanchez, A., 1987, Inf. Bull. on Var. Stars No. 3030