COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3628 Konkoly Observatory Budapest 19 June 1991 HU ISSN 0374 - 0676 PERIODIC PHENOMENA ON V373 Cep=LkH alpha 234 LIGHT CURVE Herbig Ae/Be star V373 Cep = LkHalpha 234 lies in the compact star forming region MR LkH alpha 234 associated with NGC 7129, which contains a number of T Tau stars, Herbig Ae/Be variables, Herbig-Haro objects, IR-sources and related objects (Shevchenko, Yakubov, 1989). The spectral type of O8 - A7 was assigned to V373 Cep (Shevchenko, 1989); strong and asymmetrical H alpha emission is present, EW_lambda, H_alpha= 25 A (Finkenzeller and Mundt, 1984) as well as a few faint emission lines including IR-triplet CaII, OI 8446, Paschen lines (Andrillat and Swings, 1976). V373 Cep is identified with an H_2O-maser, bipolar mass-loss source (Edwards and Snell, 1983). The light curve appears to be close to that of an irregular variable with non-periodic minima (Shevchenko and Yakubov, 1989). Our own observations of V373 Cep were made in 1983-1990 on mt. Maidanak using 0.5-m reflector with UBVR pulse counting photometer. Three 100 A/mm spectrograms were obtained using the Byurakan 2.6-m reflector with UAGS- spectrograph equipped with an image tube. Observational data are listed in Table I. 560 UBVR magnitudes were obtained for 8 years observations. The summary light curve is plotted in Figure 1. Figure 2 shows the annual light curves for 1986-1990. The same data for 1983-1985 can be found in Shevchenko and Yakubov (1989). The light curves contain waves of different duration. They were studied by means of Fourier-analysis, dispersion curve analysis and Kurochkin - Yurkevich method. Adding the measurements made by Cohen and Kuhi (1979), Racine (1968) and some other authors, the period can be suspected of 7.43 years (2720d), that is comparable with our own observational epoch. According to Shevchenko (1989) a close period (2200d) is derived from 120-yrs photographic and photoelectric observations of Herbig Ae/Be star BF Ori. The light curve of V373 Cep shows 110d waves, the first epoch being JD 2447043. The cycle of 22+-2d can be also seen in Figure 2, especially in 1987 and 1989. Figure 3 shows the light curve folded with the period of 110d for 1984-1990. It appears from the average of three spectra taken on Sep. 20, 1988 in Table I. Year Epoch n V JD 2440000+ 1983 5505 5701 49 12.11 12.89 0.14 0.88 0.98 1.65 1984 5868 6000 70 11.96 12.58 0.15 0.86 0.97 1985 6263 6386 49 12.00 12.46 0.18 0.87 1.00 1986 6617 6805 80 11.87 12.29 0.15 0.90 1.01 1.64 1987 7020 7175 82 11.94 12.49 0.16 0.90 1.02 1.68 1988 7307 7518 91 12.04 12.37 0.15 0.94 1.02 1.65 1989 7688 7887 116 12.07 12.47 0.22 0.96 1.01 1990 8049 8279 108 12.15 13.14 0.16 0.89 1.01 [FIGURE 1] Byurakan that IH alpha and EW_lambda H alpha for the star is close to those found by Cohen and Kuhi (1979) and Garrison and Andersen (1978). Strong H beta, FeII 4556, 4923.9, 5018.4, 5197.6, 5316.7, FeII+MgI 5169, FeII+CrII 5234.6, 5276 emissions are present. The strength of the H gamma absorption line corresponds to type B3 chat yields good agreement with the two-color diagram. But weak emission in this line can also be suspected. From the emission lines one expects that V373 Cep is between V380 Ori and BF Ori. [FIGURE 2] [FIGURE 3] We suggest that the periodic phenomena in V373 Cep system are caused by Keplerian rotation in the circumstellar disc accreting on the star. The 110d and 2720d periods seem to appear due to a giant protocomet and related formations moving in the protoplanet disc that leads to opacity changes in the circumstellar envelope. V.S. SHEVCHENKO, K.N. GRANKIN, M.A. IBRAGIMOV, S.Yu. MELNIKOV, S.D. YAKUBOV Tashkent Astronomical Institute, USSR N.D. MELIKYAN Byurakan Observatory, USSR References: Andrillat, I. Swings, J.P.: 1976, Astrophys. J., 204, L123. [BIBCODE 1976ApJ...204L.123A ] Cohen, M., Kuhi, L.V.: 1979, Astrophys.J. Suppl. Ser., 41, 743. [BIBCODE 1979ApJS...41..743C ] Edwards, S., Snell R.L.: 1983, Astrophys.J. 270 605. [BIBCODE 1983ApJ...270..605E ] Finkenzeller, U., Mundt, R.: 1984, Astron. Astrophys. Suppl. Ser., 55, 109. [BIBCODE 1984A&AS...55..109F ] Garrison, L.M., Andersen, C.M., 1978, Astrophys.J., 221, 601. [BIBCODE 1978ApJ...221..601G ] Racine, R.: 1968, Astrophys. J. 73, 233 [BIBCODE 1968AJ.....73..233R ] Shevchenko, V.S.: 1989, Herbig Ae/Be stars, Tashkent: "Fan". [BIBCODE 1989has..book.....S ] Shevchenko, V.S., Yakubov, S.D.: 1989, Sov. Astr., 66, 718. [BIBCODE 1989AZh....66..718S ]