COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3709 Konkoly Observatory Budapest 14 April 1992 HU ISSN 0374 - 0676 BINARIES IN THE VICINITY OF THE OPEN CLUSTER IC 4665: II. V 2203 Oph The investigation of the eclipsing variable V 2203 Oph is a continuation of our programme for studying binaries in the wide vicinity of the open cluster IC 4665 (Kraicheva et al., 1989). V 2203 Oph was discovered by Zinner (1952). Later Stiegler has found rapid light variations between 10.9m and 12.2m on the basis of 33 photographic observations. Using 184 plates taken with the 40-cm astrograph of the Crimean Station of Sternberg Institute, Moscow, in time interval JD 2442812 - 44021, Surikov (1982) classified the star as a W UMa variable with a period P = 0.455001d and light variations between 11.56m and 11.94m, Min II 11.80m. Our observations of V 2203 Oph, total number 239, in time interval JD 2444402 - 7056, were performed at the National Astronomical Observatory "Rozhen". 230 plates were taken on 50/70-cm Schmidt telescope, 9 on 2-m RCC telescope and 7 photoelectric observations with 60-cm telescope were added. Photometric measurements of the plates were carried out with the automatic iris photometer Ascoris (Carl Zeiss, Jena) at the National Observatory "Rozhen". The magnitude evaluations of some plates were made by Nijland- Blazhko method. We used Surikov's comparison stars, but our B magnitudes determined with the iris photometer are systematically smaller. These magnitudes together with the identification chart are shown in Figure 1. The measurements were based on the standard stars in cluster IC 4665 (Kazanasmas et al., 1982). UBV magnitudes of comparison stars a, b and c were measured also photoelectrically. Star No.42 was used as a check star, and No.46 as a standard one. The results are given in Table I. The results confirm V 2203 Oph as an eclipsing binary of W UMa type. A more precise value of the period of light variations was determined: P = 0.4550021d. Our observations, together with those of Surikov cover 9326 cycles. The element of light variations Min_hel I = JD 2442812.645 + 0.4550021d E satisfy well all observations between JD 2442812 end JD 2447056. During this interval the period has been unchanged. [FIGURE 1] [FIGURE 2] Table 1 B V B-V U-B a 11.16 a 10.530 0.634 0.163 b 11.50 b 10.860 0.639 0.111 c 11.85 c 11.411 0.439 0.177 d 12.12 The mean light curve of V 2203 Oph from "Rozhen" observations is presented in Figure 2 together with the individual observational data. The amplitude of the light variations was found to be 0.36m (11.50m-11.86m), Min II 11.80m. More observations of V 2203 Oph during a longer time interval are needed for studying possible variability of the period, which is a characteristic feature for W UMa type stars. Table 2 JD_hel 244.. JD_hel 244.. JD_hel 244.. JD_hel 244.. B B B B 4402.459 11.62 4760.529 11.64 5139.471 11.59 5880.416 11.57 .548 11.50 .547 11.64 171.465 11.50 .444 11.64 403.457 11.33 .548 11.64 172.531 11.59 .468 11.64 .549 11.68 .549 11.71 .421 11.59 .508 11.71 427.420 11.73 .550 11.64 173.397 11.64 801.431 11.58 428.446 11.50 .551 11.64 175.488 11.68 906.336 11.53 429.396 11.50: 761.369 11.64 195.961 11.68 .390 11.64 .425 11.52 .409 11.93 .089 11.50 .450 11.57 .455 11.68: .476 11.63 196.343 11.60 .478 11.50 430.404 11.74 .480 11.59 209.316 11.59 .507 11.50 .440 11.62 762.423 11.50 224.394 11.77: 908.519 11.57 .462 11.55 .467 11.50 226.304 11.50 936.349 11.50 455.373 11.59 779.960 11.76 437.486 11.59 995.252 11.62 .454 11.75 .398 11.85 .513 11.59 6181.546 11.68 456.383 11.68: 780.365 11.42 461.389 11.58 .565 11.42 .424 11.50 .407 11.59 .414 11.68 183.440 11.68 458.376 11.73 781.347 11.57 .437 11.68 .470 11.64 722.452 11.62 783.358 11.48 468.443 11.68 199.409 11.68 .490 11.68 .273 11.59 526.364 11.50 .449 11.90 724.430 11.62: .408 11.50 554.350 11.50 .472 11.68 .514 11.50 .442 11.50 878.363 11.50 .503 11.59 725.397 11.50: 789.338 11.57 .388 11.59 200.427 11.59 .436 11.68 823.394 11.50 .413 11.65 .453 11.69 .473 11.88 5109.388 11.49 .438 11.71 .483 11.37 .483 11.78 .436 11.59 .463 11.73 .509 11.59 .486 11.68 .470 11.62 .486 11.71 227.532 11.50 .499 11.68 .507 11.68 .510 11.62 262.445 11.68: .500 11.70 110.407 11.68 .535 11.60 286.984 11.73: .507 11.68 .495 11.66 879.351 11.85 .410 11.68 757.357 11.68 .470 11.59 .376 11.77 .435 11.55 760.431 11.50 .500 11.42 .404 11.58 .456 11.62 .468 11.64 111.506 11.59 .431 11.62 287.344 11.68 .494 11.64 .524 11.73 .457 11.60 .374 11.62 .501 11.80: 112.459 11.68 .482 11.55 .412 11.62 .508 11.77: .491 11.64 .511 11.56 288.933 11.68 .515 11.82 .525 11.64 880.341 11.59 .363 11.67 .522 11.70 139.441 11.60 .365 11.46 .388 11.68 6289.414 11.61 6554.494 11.57 6623.410 11.57 6997.429 11.62 291.305 11.62 .520 11.68 .434 11.53 998.325 11.48 .339 11.70 .545 11.63 .457 11.59 .345 11.59 293.366 11.70 .568 11.88 .481 11.68 .373 11.63 .392 11.68 .589 11.76 .505 11.71 .397 11.66 294.349 11.73 557.536 11.83 .530 11.65 7000.369 11.58 .375 11.59 .508 11.84 625.512 11.73 003.365 11.56 .400 11.58 .543 11.85 .536 11.62 032.368 11.70 295.848 11.50 .546 11.83 626.429 11.62 .394 11.63 .973 11.50 583.493 11.89 .449 11.73 033.324 11.56 .398 11.62 586.536 11.42 .498 11.68 .357 11.48 296.357 11.68 .561 11.50 .525 11.67 .420 11.61 .382 11.62 587.368 11.78 645.403 11.57 034.384 11.78 .408 11.68 .392 11.68 671.364 11.58 .405 11.80 317.328 11.68 .418 11.62 .381 11.56 038.345 11.52 .353 11.62 .432 11.57 672.308 11.50 040.432 11.40 320.373 11.42 .453 11.47 .331 11.62 054.309 11.65 321.310 11.68 .477 11.57 .383 11.68 .332 11.56 345.234 11.62 588.483 11.85 .419 11.89 055.928 11.70 .266 11.85 .531 11.68 .432 11.78 .324 11.58 554.441 11.57 .563 11.50 880.590 11.88 .349 11.51 .469 11.50 601.453 11.90 .600 11.82 056.374 11.58 .491 11.54 618.412 11.54 997.400 11.62 M. POPOVA, V. POPOV, Z. KRAICHEVA, A. ANTOV Department of Astronomy, Bulgarian Academy of Sciences 72 Trakia blvd, Sofia 1784, Bulgaria References: Kazanasmas, M., Zaverneva, L., Tomak, L.: 1982, Atlas and Catalogue of Photoelectric Standards, Kiev [BIBCODE 1982apss.book.....K ] Kraicheva, Z., Popova, M., Antov, A.: 1989, Astr. Nachr., 310, H3, 227. [BIBCODE 1989AN....310..227K ] Stiegler, Z.: Information Bank Var. Stars, Sternberg Inst., Moscow Surikov, O.G.: 1982, Per. Zvezdy Suppl., No. 20, 253. [BIBCODE 1982PZP.....4..253S ] Zinner, E.: 1952, Astr. Nachr., 281, H1, 16. [BIBCODE 1952AN....281...14Z ]