COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3494 Konkoly Observatory Budapest 20 July 1990 HU ISSN 0374 - 0676 APSIDAL MOTION OF IQ PERSEI IQ Persei (BD+47d920, HD 24909) is a bright (Vmax = +7.7 mag.) eclipsing system consisting of two main sequence stars (B8+A6) with a slightly eccentric orbit (e = 0.075) and an orbital period of 1.74 days. The very accurate orbital and stellar properties of the system have been recently determined by Lacy and Frueh (1985) on the basis of new photometric and spectroscopic observations. The results of their studies yield among other things a value for the observed apsidal motion period of U_obs =140+/-30 yr. Because Lacy's and Frueh's calculations of apsidal rotation were based only on two different epochs (about 19 years apart) of available data, we have decided to include IQ Per to our observational program to verify the value of apsidal motion of the system. The apsidal motion of an eclipsing binary is well measured from the times of primary and secondary minima. We made photoelectric observations of minima of IQ Per during the period 1888-1990. They were observed using 60-cm Cassegrain telescope of the Mt. Suhora Observatory of the Cracow Pedagogical University. The observations were carried out using a one-channel photometer (Pajdosz and Zola 1889) in 1988 and a double-beam photometer (Szymanski and Udalski 1989) in years 1988-1990. Both BD+47d918 and BD+47d923 have been served as comparison stars. Heliocentric times of minima (listed below) were determined using well known Kwee and van Woerden (KW) and graphical tracing-paper (TP) methods. Year HJD Min Type Filter Notes 1988 2447268.366+/-0.001 I V (TP) 47268.367+/-0.002 I B (TP) 1989 47783.5866+/-0.0006 II V (KW) normal 47783.5867+/-0.0008 II B (KW) normal 1990 47948.3885+/-0.0010 I B (TP) 47975.3810+/-0.0009 II B (KW) In order to investigate the period behaviour of IQ Per 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 IQ Per used in the present analysis is given in Table 1, where a weight (WGT) has been arbitrarily assigned to each minimum. If we assume that the period changes are due to apsidal motion of the system only and because of low eccentricity of the orbit of IQ Per, we can express the moments of primary and secondary minima 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. According to this equation we computed the values of M0, P, A, omega, omega0 using the least squares method, were sinusoidal curve (1) was s i m u l t a n e o u s l y fitted to both primary and secondary minima. The result is as follows : (2) HJD Min=2444290.3640 +1.7435619d*E + 0.042d*cos(0.0145deg*E + 63.6deg) +/- 4 +/- 2 +/- 2 +/- 12 +/-2.0 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 shown in Figure 1. From the relation U=360deg P/omega_dot we estimated the value of apsidal motion period to be U_obs = 119+/-9 yr and from the value of A the eccentricity of the system (assuming i=89.3deg) to be e=0.076+/-0.004. The value of e is in a good agreement with the value known from spectroscopic observations (given at the top of this paper). The theoretical estimations of U_theo using masses and radii published by Lacy and Frueh (1885) and the apsidal coefficients k1= 0.0056 and k2=0.0047 (Hejlesen 1987) yield the value 103+/-10 yr. Table I No HJD-2400000. TYPE M WGT REF No HJD-2400000. TYPE M WGT REF 1 33513.396 I :vis 1 1 37 43399.385 I vis 1 4 2 33546.500 I vis 1 1 38 43460.407 I vis 1 4 3 33900.449 I vis 1 1 39 43481.306 I vis 1 1 4 39859.933 I pe 10 2 40 43512.716 I vis 1 4 5 39866.911 I pr 10 2 41 43596.399 I vis 1 4 6 39873.885 I pe 10 2 42 43772.503 I vis 1 4 7 40222.597 I pe 10 2 43 43936.371 I vis 1 3 8 40223.5424 II +$pe 10 2 44 43957.335 I vis 1 3 9 40555.618 I pe 10 2 45 44140.405 I :vis 1 4 10 40630.592 I pe 10 2 46 44166.563 I vis 1 4 11 40637.581 I pe 10 2 47 44290.3461 I pe 10 5 12 40644.541 I pe 10 2 48 44637.303 I vis 1 4 13 41040.332 I :vis 1 1 49 44853.5193 I pe 10 1 14 41230.389 I vis 1 1 50 44925.907 II +pe 10 6 15 41244.338 I :vis 1 1 51 44926.749 I pe 10 8 16 41249.567 I vis 1 1 52 45622.425 I vis 1 4 17 41373.358 I vis 1 1 53 45636.401 I vis 1 4 18 41603.504 I vis 1 1 54 45983.359 I vis 1 4 19 41673.266 I vis 1 3 55 46112.3767 I pe 10 4 20 41699.391 I vis 1 3 56 46405.293 I vis 1 1 21 41753.455 I :vis 1 3 57 46717.391 I vis 1 1 22 41781.354 I vis 1 1 58 46731.348 I vis 1 1 23 41971.394 I vis 1 3 59 46764.486 I vis 1 1 24 42060.338 I vis 1 1 60 47029.490 I vis 1 1 25 42074.275 I vis 1 3 61 47057.388 I :vis 1 1 26 42262.576 I vis 1 3 62 47064.348 I vis 1 1 27 42283.498 I vis 1 1 63 47102.7277 I pe 10 7 28 42283.513 I vis 1 1 64 47151.551 I vis 1 1 29 42414.250 I vis 1 1 65 47207.328 I vis 1 1 30 42433.447 I vis 1 4 66 47207.334 I :vis 1 1 31 42461.318 I vis 1 3 67 47207.345 I vis 1 1 32 42461.334 I vis 1 4 68 47288.3665 1 pe 10 8 33 42740.304 I vis 1 3 69 47783.5867 II $pe 10 8 34 42787.390 I vis 1 3 70 47948.3595 I pe 10 8 35 43141.351 I vis 1 4 71 47975.3810 II pe 10 8 36 43174.462 I pe 10 1 Notes: (:)-uncertain, ($)-normal minimum, (+)-derived from original observations (1) B.A.V. observers, (2) Hall et al. (1970), (3) B.B.S.A.G. observers, (4) B.A.A.V.S.S. observers, (5) Pohl et al. (1982), (6) Lacy and Frueh (1985), (7) Caton et al. (1989), (8) this paper [FIGURE 1] This work has been partly supported by the Polish Academy of Sciences (grant CPBP 01.11). M. DROZDZ, J. KRZESINSKI and G. PAJDOSZ Institute of Physics, Pedagogical University Cracow. POLAND. References: Caton, D. B., Hawkins, R. L., and Burns, W. C., 1989, I.B.V.S. No. 3408. Hall, D. S., Gertken, R. H., and Burke, E. W., 1970, P.A.S.P. 82. 1077. [BIBCODE 1970PASP...82.1077H ] Hejlesen, P. M., 1987, A.Ap. Suppl. 69, 251. [BIBCODE 1987A&AS...69..251H ] Lacy, C.H., and Frueh, M.L., 1955, Ap.J. 295, 569. [BIBCODE 1985ApJ...295..569L ] Martynov, D.Ya., 1971, in "Zatmennyje peremennye zwezdy", ed. V.P. Zessewich. Moscow, p.325. Pajdosz, G., and Zola, S., 1989, I.B.V.S. No. 3251. Pohl, E., Evren, S., Tumer, O., and Sezer, C., 1982, I.B.V.S. No. 2189. Szymanski, M., and Udalski, A., 1989, Acta Astr. 39, 1. [BIBCODE 1989AcA....39....1S ]