COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2886 Konkoly Observatory Budapest 9 April 1986 HU ISSN 0374 - 0676 AH CEPHEI: A NEW PHOTOMETRIC TRIPLE STAR The period of the bright early-type eclipsing binary AH Cep was discussed several years ago by Mayer and Tremko (1983) and thought to vary irregularly. however, the recent times of minima obtained with our Department's 65 cm telescope in Ondrejov strongly suggest another explanation. All published minima, i.e. those from papers by Mayer (1980) and Mayer and Tremko, as well as the new minima are given in Table I. In the column O-C1 the comparison with the ephemeris found by Guarnieri et al. (1975) is presented: Min. I = J.D.hel. 2434989.404 + 1.774759d E (1) [FIGURE 1] Table I Minima of AH Cep J.D.hel. +2400000 E O-C1 O-C2 O-C3 W Source 15500.11: -10981.5 +.222 -.0090 -.0024 1 1 24076.621 - 6149 +.210 +.0647 +.0151 1 2 25388.089 - 5410 +.131 -.0012 -.0129 2 3 25835.345 - 5158 +.148 +.0200 +.0189 1 1 26440.487 - 4817 +.097 -.0248 -.0135 1 1 26564.728 - 4747 +.105 -.0157 -.0021 1 1 26985.34 - 4510 +.099 -.0174 +.0034 1 1 34714.309 - 155 -.007 -.0467 -.0047 2 4 34981.420 - 4.5 +.002 -.0343 +.0058 2 5 34989.404 0 .000 -.0366 +.0035 3 5 40873.619 3315.5 +.0015 +.0236 -.0077 3 6 41196.637 3497.5 +.014 +.0388 +.0023 2 7 42647.507 4315 +.018 +.0577 -.0027 2 7 43779.813 4953 +.028 +.0787 +.0014 1 8 43815.3153 4973 +.0348 +.0862 +.0085 3 7 44010.532 5083 +.028 +.0814 +.0014 2 9 45200.499 5753.5 +.020 +.0844 -.0010 2 9 45223.570 5766.5 +.019 +.0837 -.0016 2 9 45562.5380 5957.5 +.0073 +.0761 -.0060 3 9 45579.398 5967 +.008 +.0761 -.0058 2 9 46343.4150 6397.5 -.0097 +.0670 +.0019 3 10 46358.5006 6406 -.0090 +.0672 +.0026 3 10 46359.3887 6406.5 -.0088 +.0680 +.0034 3 10 Sources: 1- Zverev (1933), 2 - Moore (1936), 3- Huffer and Eggen (1947), 4- Nekrasova (1960), 5- Guarnieri et al.(1975), 6- Battistini et al.(1974), 7- Mayer (1980), 8- Hartigan and Binzel (1982), 9- Mayer end Tremko (1983), 10- this paper. Values in the column O-C2 are obtained using the ephemeris Min. I = J.D.hel. 2434989.4406 + 1.7747413d E (2) +- 20 + 18 These values are also plotted in Fig. 1. The curve drawn in this figure corresponds to a third-body light time effect, with the third-body orbit of the following parameters: P - (12830 +- 170).P0, i.e. 62.3 +- 0.8 years T0 (time of periastron) = J.D. 2445890 +- 360 e = 0.534 +- 0.023 omega = 125deg+-8 The semiamplitude of the light time effect is 0.0694d +- 0.0024d. These values were obtained together with the ephemeris (2) by the least squares method. Weights applied in the solution are given in the column W. They are assigned according to the estimated accuracy o of the times of minima: W= 1 for sigma > 0.01d, W= 2 for 0.01d>sigma>0.001d, and W= 3 for sigma<0.001d. The corresponding O-C values may be found in the column O-C3. Mean errors are given. We realize that in several systems the explanation of period changes by a third body proved to be untenable when newer data were secured. In this case one must also see that the early times of minima are rather inaccurate. Therefore the significance of the favourable fact that the data now cover 1.4 of the long period is impaired. However, the present explanation is supported by the quite reasonable value of the mass function f(m3) = 0.45, from which the minimum mass of the third body follows as 8 Msun (under assumption m1+m2= 25 Msun, as can be estimated from data collected by Batten et al. (1978)). If the new explanation is correct, then the period of AH Cep should be nearly constant in the next 6-7 years, having the value of about 1.77468. In the column O-C3 one can see that the remaining differences - namely those of weight 3 - are larger than the observing errors. This could perhaps be again explained by a periodic behaviour; a period of 668 days, with amplitude 0.0060d suits the data quite well. The corresponding fourth body would have a minimum mass of 7 Msun. The number of good measurements is, however, rather low, so the presence of this body should yet be proven. PAVEL MAYER and MAREK WOLF Department of Astronomy and Astrophysics Charles University Svedska 8, 15000 Praha 5, Czechoslovakia References: Batten, A.H., Fletcher, J.M., and Mann, P.J., 1978, Publ. Dominion Astrophys. Obs. Victoria, 15, 121. [BIBCODE 1978PDAO...15..121B ] Battistini, P., Bonifazi, A., and Guarnieri, A., 1974, Inf. Bull. Var. Stars, No. 817. Guarnieri, A., Bonifazi, A., Battistini, P., 1975, Astron. Astrophys. Suppl. Ser., 20, 199. [BIBCODE 1975A&AS...20..199G ] Hartigan, P., and Binzel, R.P., 1982, Journal. AAVSO, 11, 21. [BIBCODE 1982JAVSO..11...21H ] Huffer, C.M., and Eggen., O.J., 1947., Astrophys. J., 106. 313. [BIBCODE 1947ApJ...106..313H ] Mayer, P., 1980, Bull. Astr. Inst. Czechoslovakia, 31, 292. [BIBCODE 1980BAICz..31..292M ] Mayer, P., and Tremko, J., 1983, Inf. Bull. Var. Stars, No. 2407. Moore, J.H., 1936, Lick Obs. Bull., 16, 483. Nekrasova, S.V., 1960, Perem Zvezdy, 13, 157. [BIBCODE 1960PZ.....13..157N ] Zverev, M, 1933, Perem Zvezdy, 4, 177.