COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2075 Konkoly Observatory Budapest 1982 January 22 HU ISSN 0374-0676 V 1068 CYGNI - A LONG-PERIOD RS CVn STAR? On the long-period eclipsing binary V 1068 Cygni (= BD +41d4100) there was published a report in this Bulletin by D. Hoffleit (1). More recent investigations of this star were made by R. Diethelm (2) and by B. Fuhrmann (3). First photoelectric UBV observations of the object were obtained by the author with the Sonneberg 60 cm telescope II and the Piszkesteto (Hungary) 50 cm telescope in the years 1979 to 1981 (see Table I). The comparison star BD +41d4108 was linked to BD +42d4081 with magnitudes from (4). The magnitudes found for BD +41d4108 are: V = 9.49m, B-V = +1.07m, U-B = +0.76m. Figure 1 shows the mean light curves (outside eclipse) for the separate years computed with the elements given by B. Fuhrmann (3). There is an indication of a migrating [FIGURE 1] wavelike distortion as it occurs in RS CVn type stars. With respect to the period of 42.7 days the system would then be a member of the long-period RS CVn group. Table I ------------------------------------------------------ year J.D.hel. V B-V U-B phase 2444000+ ------------------------------------------------------ 1979 136.397 10.29 +1.14 - .6729 143.352 10.28 +1.19 - .8358 155.380 10.40 +1.12 +0.80: .1176 x 157.328 10.37 +1.14 +0.78: .1633 x 167.328 10.36 +1.14 +0.75 .3976 x 171.274 10.36 +1.14 +0.76: .4900 x 172.275 10.36 +1.12 +0.78 .5135 x 173.301 10.36 +1.12 +0.68 .5375 x 174.253 10.35 +1.08 +0.80: .5598 x 1980 374.526 10.25 +1.21 +0.89 .2521 485.379 10.31 +1.15 +0.68 .8493 486.376 10.31 +1.18 +0.65 .8727 490.326 10.57 +1.44 +1.03: .9652 491.397 10.55 +1.49 +1.03 .9903 508.460 10.30: +1.16: +0.66: .3901 x 512.302 10.32 +1.15 +0.77 .4801 x 516.504 10.34 +1.15 +0.69 .5786 x 545.280 10.28 +1.17 - .2528 571.344 10.32 +1.17 +0.74 .8634 575.313 10.46 +1.36 +0.96 .9564 577.308 10.58 +1.43 +1.00 .0032 590.297 10.29 +1.17 +0.69 .3075 1981 769.473 10.37 +1.16 +0.66 .5055 783.545 10.33 +1.16 +0.71 .8352 787.545 10.33 +1.14 +0.64 .9289 829.422 10.32 +1.17 +0.69 .9101 851.340 10.33 +1.13 +0.74 .4236 852.329 10.35 +1.13 +0.71 .4468 853.335 10.35 +1.15 +0.72 .4703 854.305 10.34 +1.16 +0.69 .4931 886.393 10.30 +1.17 +0.71 .2449 923.229 10.34 +1.16 +0.76 .1079 925.342 10.31 +1.19 +0.72 .1574 ----------------------------------------------------- : uncertain values x observed at Piszkesteto Moreover P. Notni kindly took image tube spectra at the Tautenburg 2 m telescope with a dispersion of 140 A/mm on 1980 April 15 (24.5 days past minimum) and 1980 December 3 (in minimum phase). The first spectrum is composite and indicates a spectral class B5 to A5 + G8 II-III in accordance with (1). The second spectrum also seems to be composite, but the Balmer lines of the hotter component are clearly weaker. Unfortunately the spectra do not reach the CaII lines H and K, so it is impossible to decide on the presence of emission in those lines, which would be an important criterion of RS CVn stars and related objects. Further spectroscopic investigation is desirable. Emission in other lines could not be found. If we assume that the hotter component of the system has physical properties of a normal main sequence star and that the colour excess ratio E_U-B / E_B-V for hotter component attains the normal value of 0.7, then the observed minimum depths in the three colours, DeltaV = 0.30m, DeltaB = 0.58m, DeltaU = 0.93m, are well to reproduce by a B9.5 V component (M_V = 0.7m) and a G8 II-III component (M_V = -0.3m). In this case the hotter component is eclipsed in the centre of the minimum phase about 85%. From the colour excess E_B-V = 0.62m follows A_V = 3.E_B-V = 1.9m. The maximum apparent brightness of the hotter component alone is, after the computed model, V_max = 11.65m. This amounts to a distance to the system of 650 pc. S. ROSSIGER Sternwarte Sonneberg Zentralinstitut fur Astrophysik der Akademie der Wissenschaften der DDR References: (1) Hoffleit, D., 1977, IBVS No. 1282 (2) Diethelm, R., 1977, BBSAG Bull. 35, 6 (3) Fuhrmann, B., 1980, M.V.S. 8, 186 (4) Sanders, W.L., 1966, A.J. 71, 719 [BIBCODE 1966AJ.....71..719S ]