COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3495 Konkoly Observatory Budapest 20 July 1990 HU ISSN 0374 - 0676 APSIDAL MOTION OF AS CAMELOPARDALIS AS Cam (BD+69d325, HD 35311, Vmax= +8.6) is a detached eclipsing binary consisting of two components of spectral types B8V and B9.5V in an eccentric orbit (e=0.135) and with orbital period equal to 3.43 days. The spectroscopic orbit of this system was determined by Hilditch (1972). The last photometric studies have been made by Khaliullin and Kozyreva (1983). The apsidal motion of AS Cam has been recently discussed by Maloney et al. (1959). The authors used all the published timings of primary and secondary minima from 1899 to 1986 and confirmed a significant discrepancy between the observed value of periastron motion Uobs= 2400+/-850 yr and the theoretical one predicted by classical and general relativistic effects of Utheo= 815+/-61 yr. The cause of this discrepancy remained an unsolved problem (Maloney et al. 1989). We observed AS Cam during two nights in January and April 1990. The observations were carried out at Mt. Suhora Astronomical Observatory of the Cracow Pedagogical University using the 60-cm Cassegrain telescope with a double-beam photometer (Szymanski and Udalski 1989). BD+69d323 was chosen as the comparison star. Two heliocentric moments of minima were computed using the Kwee and van Woerden method: HJD Min Type Filter 2447898.2528+/-0.0002 II V 47982.5118+/-0.0004 I B In order to investigate the period changes of AS Cam we have collected all minima available in the literature. Minima observed in different filters but in the same epoch were averaged. The final list of minima of AS Cam used in the present analysis is given in Table 1, where a weight (WGT) has been arbitrarily assigned to each minimum. In the next step we have assumed that the period changes are due to apsidal motion of the system only. The moments of both primary and secondary minima can be expressed by the approximate formulae (Martynov 1971): (1) -A*cos(omega_dot*E+omega0) - for primary min (E is integer) / HJDMin= M0+P*E \ +A*cos(omega_dot*E+omega0) - for secondary min (E is halfed) where: A = P*e*(1 + cosec^2*i)/ 2*pi. In the equation (1) we omitted terms of the order of e^2 and higher because of the low eccentricity of the orbit of AS Cam as well as a small interval of the observations in relation to the apsidal motion period. The values of M0, P, A, omega. omega0 were adjusted s i m u l t a n e o u s l y for both primary and secondary minima by means of the least squares method. The following parameters were obtained: (2) HJD Min=2440204.4062 + 3.4309691 * E +/- 0.111*cos(0.0037*E+198) +/-10 +/-7 +/-7 +/-18 +/-10 The theoretical O-C curves for obtained parameters along with the observed O-C computed according to the linear elements given in eq.(2) are plotted in Figure 1 where only points with non-zero weight were presented. From the relation U=360 P/omega_dot we estimated the value of apsidal motion period to be Uobs= 920+/-470 yr and from the value of A the eccentricity of the system (assuming i=89deg) to be e = 0.10+/-0.01. In fact, a real value of e can be different from the presented value due to emission of the last terms in eq. (1). Nevertheless, our estimation showed that this difference should not be greater than 10%. The obtained value of e is significantly lesser than those known from photometric investigations (e=0.17) by Khaliullin and Kozyreva (1983) and used by Maloney et al. (1989) in their analysis of apsidal motion of AS Cam and those determined spectroscopically (e=0.135) by Hilditch (1972). The Table I No HJD-2400000. TYPE N WGT REF No HJD-2400000. TYPE N WGT REF 1 15120.678 I ptg 0 1 36 32937.702 I ptg 1 1 2 15770.643 II ptg 1 1 37 36612.310 I ptg 1 1 3 16166.718 I ptg 0 1 38 39859.4902 II pe 10 1 4 16359.309 I $ptg 1 2 39 39890.3692 II pe 10 1 5 16360.754 II $ptg 1 2 40 39924.6814 II pe 10 1 6 16456.772 II ptg 0 1 41 40132.4604 I pe 10 1 7 16537.619 I ptg 1 1 42 40204.5137 I pe 10 1 8 16775.745 II ptg 0 1 43 40269.6996 I pe 10 1 9 17259.639 II ptg 1 1 44 40626.5223 I pe 10 3 10 18284.810 I ptg 0 1 45 40911.297 I pe 10 4 11 18431.585 I ptg 1 1 46 40957.393 II pe 10 4 12 18592.837 I ptg 1 1 47 40959.327 I pe 10 4 13 18750.564 I ptg 1 1 48 40988.276 II pe 10 4 14 20226.021 I $ptg 1 2 49 40990.202 I pe 10 4 15 20227.459 II $ptg 1 2 50 40995.138 II pe 10 4 16 20901.706 I ptg 0 1 51 41007.3600 I pe 10 3 17 21577.777 I ptg 1 1 52 41547.5278 II pe 10 5 18 22380.615 I ptg 1 1 53 41578.4065 II pe 10 5 19 22920.719 II ptg 1 1 54 41580.3334 I pe 10 5 20 23042.746 I ptg 1 1 55 42460.4200 I :vis 0 6 21 24648.596 I ptg 1 1 56 44939.2415 I pe 10 7 22 24991.572 I ptg 1 1 51 44940.7526 II pe 10 7 23 26000.306 I ptg 1 1 58 45002.514 II pe 10 8 24 26238.450 II ptg 1 1 59 46397.4085 I pe 10 9 25 26303.770 II ptg 1 1 60 46500.331 I pe 10 6 26 26422.379 I ptg 1 1 61 46771.3810 I pe 10 10 27 26751.617 I ptg 1 1 62 47138.4956 I pe 10 11 28 26753.583 II ptg 0 1 63 47270.3851 II pe 10 6 29 26988.454 I ptg 1 1 64 47443.8483 I pe 10 12 30 27187.554 I ptg 0 1 65 47465.9520 II pe 10 12 31 28127.474 I ptg 1 1 66 47553.6410 I pe 10 13 32 29194.531 I ptg 1 1 67 47893.314 I pe 10 6 33 29204.819 I ptg 1 1 68 47898.2528 II pe 10 14 34 30381.870 I ptg 0 1 69 47982.5118 I pe 10 14 35 32275.546 I ptg 1 1 Notes: (:)- uncertain, ($)- normal minimum (1) Hilditch (1969), (2) Maloney et al. (1989), (3) Battistini et al. (1974), (4) Padalia and Srivastava (1975), (5) Gulmen et al. (1976), (6) B.B.S.A.G. observers, (7) Khaliullin and Kozyreva (1983), (8) Pohl et al. (1983), (9) B.A.A.V.V.S. observers, (10) Guinan et al. (1987), (11) BAV observers, (12) Lines et al. (1989), (13) Couls (1989), (14) this paper theoretical estimations of Utheo using our value of e=0.10 yield the period of apsidal motion equal to 900+/-70yr. Our analysis shows no differences between theory and observations. The cause of the anomalies obtained in earlier determinations of apsidal rotation of AS Cam might be due to the incorrect value of the orbital eccentricity of the system. It may be interesting to check our result by now spectroscopic and photometric observations. [FIGURE 1] This work has been partly supported by the Polish Academy of Sciences (grant CPBP 01.11). J. KRZESINSKI, E. KUCZAWSKA, and G. PAJDOSZ Institute of Physics, Pedagogical University Cracow, POLAND References Battistini, P., Bonifazi, A., and Guarnieri, A., 1974, I.B.V.S. No. 951. Couls, C. J., 1989, I.B.V.S. No. 3369. Guinan, E. F., Maloney, F. P, and Boyd, P. T., 1887, I.B.V.S. No. 3029. Gulmen, O., Ibanoglu, C., Bozkurt, S., and Gudur, N. 1976, I.B.V.S. No. 1090. Hilditch, R. W., 1969, Observatory 89, 143. [BIBCODE 1969Obs....89..143H ] Hilditch, R. W., 1972, P.A.S.P. 84, 519. [BIBCODE 1972PASP...84..519H ] Khaliullin, Kh. F., and Kozyreva, V. S., 1983, Ap.Sp.Sci. 94, 115. [BIBCODE 1983Ap&SS..94..115K ] Lines, H. C., Lines, R. D., Glownia, Z., and Guinan, E. F., 1989, P.A.S.P. 101. 925. [BIBCODE 1989PASP..101..925L ] Maloney, F. P., Guinan, E. F., and Boyd, P. T., 1989, A.J. 98, 1800. [BIBCODE 1989AJ.....98.1800M ] Martynov, D.Ya., 1971, in "Zatmennye peremennye zwezdy". ed. V.P. Zessewitch, Moscow, p.325. Padalia, T.D., and Srivastava, R.K., 1975, Ap.Sp.Sci. 38, 87. [BIBCODE 1975Ap&SS..38...87P ] Pohl, E., Hamzaoglu, E., Gudur, N., and Ibanoglu, C., 1983, I.B.V.S. No. 2385. Szymanski, M., and Udalski, A., 1989, Acta Astr.,39, 1. [BIBCODE 1989AcA....39....1S ]