COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3544 Konkoly Observatory Budapest 21 November 1990 HU ISSN 0374 - 0676 BV LIGHT CURVES AND THE FIRST EPHEMERIS FOR THE ECLIPSING BINARY STAR NSV 1776 NSV 1776 (CSV 464) was discovered by Shapley in 1938 on photographic plates taken at the Harvard Observatory. The coordinates for the 2000.0 epoch are: alpha=4h56m06s delta=+10d05.9' The New Catalogue of Suspected Variable Stars (Kukarkin et al., 1982) classifies that star as a possible eclipsing binary, with a magnitude range 12.6 - 13.5 (p); the period is unknown. From 925 visual estimates performed by 9 observers of the GEOS since 1987, 20 minima have been obtained, confirming the eclipsing binary nature of NSV 1776. To improve the period and obtain BV light curves, photoelectric measurements were made at the Jungfraujoch Observatory, by M. Dumont and R. Boninsegna. The measurements were performed with a photometer attached to a 76 cm telescope. B and V filter values of the Geneva system, and the B-V values have been converted into Johnson and Morgan's system. 102 photoelectric measurements were obtained in each colour on 12 nights between 1987 and 1989. Two minima were determined with a difference in amplitude close to 0.15 magnitude in V-light. The discrimination of both minima being possible, the period can be derived from the 20 visual and the 2 photoelectric minima, weighting the last two by 3. A first ephemeris has been computed using these 22 times of minimum light: Min I = hel. J.D. 2447888.512 + 1.10245d * E (1) +- 4 +- 2 (95% level of confidence for error bars) Figure 1 shows V and B-V light curves of NSV 1776, according to the ephemeris (1). Table I lists the 22 minima (vis = visual, ph = photoelectric) and the O-C's referring to the ephemeris above. One can see the good agreement between visual and photoelectric observations. The mean B-V value, not corrected for reddening is 0.58. [FIGURE 1a] FIG 1A: V LIGHT-CURVE OF NSV 1776, ACCORDING TO THE EPHEMERIS (1). [FIGURE 1b] FIG 1b: B-V LIGHT-CURVE OF NSV 1776, ACCORDING TO THE EPHEMERIS (1). TABLE I Times of Minimum Light, According To The Following Ephemeris: MIN (Hel) = 24 47 888.512 + 1.10245 * E (1) +- 4 +- 2 JD HEL. Cycles Type O-C (1) Obs. 2400000+.. 47469.592 -380 I +0.012 vis 47479.509 -371 I +0.007 vis 47480.593 -370 I -0.012 vis 47502.643 -350 I -0.011 vis 47533.509 -322 I -0.014 vis 47542.339 -314 I -0.003 vis 47553.369 -304 I +0.002 vis 47558.328 -299.5 II +0.0004 vis 47558.338 -299.5 II +0.01 vis 47565.494 -293 I +0.0004 vis 47568.249 -290.5 II -0.001 vis 47596.356 -265 I -0.006 vis 47596.365 -265 I +0.003 vis 47596.377 -265 I +0.015 vis 47885.444 -30 I +0.006 vis 47887.408 -1 I -0.001 vis 47888.5056 0 I -0.006 ph. 47888.512 0 I +0.0004 vis 47891.279 +2.5 II +0.011 vis 47892.3646 +3.5 II -0.006 ph. 47908.566 +18 I +0.01 vis 47945.293 +51.5 II +0.005 vis With its typical V-light curve and the quasi-constant B-V index, which does not vary during the eclipses, NSV 1776 can be catalogued as a new EA- type eclipsing binary variable, with the following elements: magnitude range: 11.88 - 12.76 in V light (min II: 12.59 V) Duration of the eclipses: D_I = 0.20 P d_II = 0.18 P G. BOISTEL (1), R. BONINSEGNA (1), M. DUMONT (1,2) 1 GEOS 2 Palais de la Decouverte 3, Promenade Venezia Av Franklin D. Roosevelt F-78000 Versailles F-75008 Paris References: Kukarkin, B.V., Kholopov, P.N.: 1982, New Catalogue of Suspected Variable Stars (Moscow "Nauka"). [BIBCODE 1982ncsv.book.....K ] Shapley, H., Hanley, C.M.: 1938, Harvard Bulletin 913, p.9 [BIBCODE 1940BHarO.913....9H ] [DATAFILE 2]