COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 956 Konkoly Observatory Budapest 1975 January 15 RZ Eri This eclipsing binary with a period of 39 days consists of an early type primary and a late type secondary with CaII H and K in emission. Cesco and Sahade (1945) studied the system spectroscopically and determined an orbit for the primary component. Later Gaposchkin (1951) and Gadomski (1957) derived photometric elements from photographic observations. As the light curve shows total primary eclipses it is possible from a few observations to determine photometric indices for the two components. In the bottom of primary eclipse we measure only the light of the cool secondary and by subtracting this light from the out-of- eclipse observations we get the light of the primary. In November, 1973 observations were carried out on six nights around a primary minimum which was predicted to happen at HJD 2442002.89. The observations were obtained by means of the Copenhagen 50 cm telescope at Cerro La Silla and a four channel uvby-photometer. HR 1545 was used as a comparison star. Table 1 lists the observations. Table 1 RZ Eri - HR 1545 HJD 24 Delta(u) Delta(v) Delta(b) Delta(y) Phase 42000.796 2.274 1.774 1.579 1.450 000.827 2.280 1.770 1.582 1.454 001.743 2.296 1.782 1.591 1.459 partial 001.793 2.318 1.805 1.612 1.476 partial 002.673 3.944 3.452 2.843 2.453 total 002.730 3.928 3.450 2.834 2.452 total 002.752 3.918 3.439 2.836 2.438 total 002.815 3.929 3.449 2.844 2.452 total 003.754 2.355 1.840 1.640 1.498 partial 004.672 2.276 1.766 1.576 1.445 005.759 2.268 1.768 1.573 1.444 From observations of standard stars we derive for HR 1545: V = 6.261 b-y = 0.302 m_1 = 0.139 c_1 = 0.411, hence we get for the two components of RZ Eri: Primary: V = 8.26 b-y = 0.285 m_1 = 0.200 c_1 = 0.867 Secondary: V = 8.71 b-y = 0.717 m_1 = 0.307 c_1 = 0.340. The ([m_1]), [c_1]) indices for the primary component correspond to an F5 giant or an Am star. This may be compared with the classification by Morgan (Cesco and Sahade, 1945), who finds a spectral type of F5 from the metallic lines alone but A5 from the H/K ratio, indicating a metal-line star. Popper once questioned this (1967), but in a recent private communication (1974), he no longer disputes Morgan's classification. Thus the problem of spectral type of the primary component is still not solved. The indices of the secondary correspond to a K giant. BENT GRONBECH Copenhagen University Observatory and European Southern Observatory References: Cesco, C.U. and Sahade, J. : Ap.J. 101, 370 (1945). [BIBCODE 1945ApJ...101..370C ] Gadomski, J. : Acta Astron. 7, 83 (1957). [BIBCODE 1957AcA.....7...83G ] Gaposchkin, S. : Harvard Bull. No. 920 (1951). Popper, D.M. : PASP 74, 129 (1962). [BIBCODE 1962PASP...74..129P ] Popper, D.M. Private communication (1974). TIMES OF MINIMA FOR V523 Sgr AND V526 Sgr The following observations of apsidal motion systems were obtained by means of the 50 cm Copenhagen Telescope at Cerro La Silla, Chile and a four channel uvby photometer. Each time of minimum is the mean for all four colours. V523 Sgr. A primary minimum was observed at Min I: HJD 24 41836.8745 +- 4 The latest discussion of the apsidal motion is given by de Kort (1956), who arrived at an apsidal motion period of 248 years and eccentricity 0.2. Using the revised phase formula we obtain by plotting in his Fig.2. an O-C of about -.02p, indicating an eccentricity slightly lower than 0.2. V526 Sgr. Two minima were observed as follows: Min II::HJD 24 41828.7271 O-C=-.0027d +- 3 Min I : HJD 24 41829.9003 O-C=+.0105d +- 2 An extensive discussion of the apsidal motion is given by O'Connell (1967). The residuals to his ephemeris (formula 4) are given above, and although they seem to be quite large, it is probably not possible to improve the apsidal motion parameters significantly with the material available. BENT GRONBECH Copenhagen University Observatory and European Southern Observatory References: de Kort, J. 1956: Vistas in Astronomy, 2, 1187. [BIBCODE 1956VA......2.1187D ] O'Connell, D.J.K. 1967: Ricerche Astron., 7, No. 11. [BIBCODE 1967RA......7..339O ]