COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3900 Konkoly Observatory Budapest 21 June 1993 HU ISSN 0374 - 0676 TIMES OF MINIMUM LIGHT FOR 35 ECLIPSES OF 21 APSIDAL MOTION BINARIES We report here on the continuation of a program of observing eclipsing binary systems suggested by Gimenez and Delgado (1980), and by Gimenez (1985), as candidates for possible detection of general-relativistic apsidal motion. Additional systems were observed from the table of Hegedus (1988). This paper tabulates results since the last publication by Caton et al. (1989). The observations were made with the same equipment described in that paper. The observations for a given eclipse were made through the V filter only, to maximize the number of data points. The observations have not been transformed to the Johnson system, since they were only intended for timing analysis. The observations are available from the IAU Archives, file number 248. The times of minimum light and standard errors given in Table I were calculated using the method of Kwee and van Woerden (1956), using a program written by Ghedini (1982). This algorithm has been shown by Caton (1989) to give the most accurate estimation of time of conjunction for asymmetric light curves. The values of O-C were computed using the epoch and period in the fourth edition of the General Catalog of Variable Stars (Kholopov, 1985-87). The value of each O-C is listed to a precision usually limited by the precision of the published epoch. Table I System Type of Heliocentric O-C Comparison Eclipse (-2400000) (days) Star BW Boo Primary 48341.66516 -0.0109 BD+37d2551 +/-0.00020 UW Boo Primary 48362.65544 +0.0074 BD+47d2135 +/-0.00029 AS Cam Primary 48191.80069 -0.01443 BD+69d0323 +/-0.00028 Secondary 48601.60190 " +/-0.00025 PV Cas Secondary 48208.65307 BD+58d2555 +/-0.00013 Primary 48237.54912 -0.0054 " +/-0.00093 Table I (cont.) System Type of Heliocentric O-C Comparison Eclipse (-2400000) (days) Star PV Cas Primary 48538.61836 -0.0169 BD+58d2555 +/-0.00058 V459 Cas Primary 48209.67110 -0.072 BD+60d0178 +/-0.00009 EK Cep Primary 47840.60313 +0.0051 BD+68d1239 +/-0.00049 Primary 48234.67627 +0.0047 " +/-0.00012 CW Cep Primary 48197.65350 -0.0250 BD+62d2162 +/-0.00017 V1143 Cyg Primary 48019.73800 -0.0057 BD+54d2187 +/-0.00011 Y Cyg Primary 48528.73157 +0.1363 BD+34d4190 +/-0.00043 HS Her Primary 48744.77194 -0.0073 BD+24d3538 +/-0.00031 Secondary 49105.81612 +/-0.00025 DI Her Primary 48816.65450 +0.0021 BD+24d3567 +/-0.00043 u Her Secondary 48746.74837 BD+32d2896 +/-0.00019 Secondary 48022.72852 BD+32d2896 +/-0.00092 TX Leo Primary 49037.78855 +0.0421 BD+10d2166 +/-0.00009 XX Leo Primary 48352.70823 See note BD+14d2198 +/-0.00018 Primary 48690.66135 " +/-0.00039 Secondary 48705.71009 " +/-0.00049 Secondary 48741.64571 " +/-0.00019 RR Lyn Primary 48936.69194 -0.0107 BD+56d1136 +/-0.00026 U Oph Primary 48765.75180 +0.0068 BD+02d3283 +/-0.00015 FT Ori Secondary 47840.80454 BD+21d1161 +/-0.00017 Table I cont. System Type of Heliocentric O-C Comparison Eclipse (-2400000) (days) Star FT Ori Primary 48279.59924 +0.00252 BD+21d1161 +/-0.00020 Primary 48282.75125 +0.00412 " +/-0.00047 AG Per Primary 48195.71090 +0.026 BD+33d776 +/-0.00019 Secondary 48196.81694 " +/-0.00131 Secondary 47843.81937 " +/-0.00125 IQ Per Primary 48183.74166 +0.0035 BD+47d923 +/-0.00028 Secondary 48196.81612 " +/-0.00142 TX UMa Primary 48324.90636 +0.0822 BD+46d1658 +/-0.00017 DR Vul Primary 48536.69947 +0.118 BD+26d3827 +/-0.00078 Notes (1) The primary for AS Cam has a residual of -0.0156 days, and the secondary has a residual of -0.0098 when computed from the light elements of Maloney et al. (1989), continuing the slow migration to negative residuals that they noted. (2) The times of minimum for the primaries of PV Cas are in reasonable agreement with the ephemerides of Gimenez and Margrave (1982), with (O-C)s of +0.0014 and -0.0004 days for JD 48237 and 48538, respectively. These are within the formal errors shown in Table I. The secondary's O-C from Gimenez and Margrave's prediction is -0.0013 days. We note that this is an order of magnitude larger than the formal error, the latter being determined from over a hundred measurements taken over 4.5 hours with good observing conditions (the V extinction coefficient, determined from the comparison star, was 0.12 mag/air mass with a standard error of 0.006). The mean difference in magnitude between the comparison and check star (BD +58d2561) for 24 measurements during the event was 0.088 +/-0.009 magnitudes. (3) In observing XX Leo it was found that the light elements in the General Catalog lead to an eclipse prediction off by about a half a cycle. We were able to observe enough events to determine that the current period is 0.9711296 days. (4) Sharp-eyed readers will note two virtually simultaneous events observed on JD 2449196 - AG Per and IQ Per. On that night both events were observed by taking two variable measurements, bracketed by comparisons and skies, alternately on one system and the other. This reduced the number of data points but appears to not have greatly affected the result. The error, for 29 points was half the error for JD 2447843, which had over a hundred measurements. However, the seeing conditions on that night, with (check star minus comparison) residuals of 0.008 magnitudes, were apparently not as good as on the two-event night, which had residuals of 0.004 magnitudes. On both nights the check star, BD +32d0714, was measured to be 0223 magnitudes fainter than the comparison. (5) The residual for TX UMa is -0.202 days when computed from the linear formula used by Todoran and Roman (1992), placing it a little above the last and lowest point in their O-C diagram (their Figure 1). We would like to thank Mr. R. L. Hawkins and Mr. John Gullett for helping with some of the observations. We gratefully acknowledge the assistance of the staff at the U.S. Naval Observatory Library, in providing reference material. This research has made use of the Simbad database, operated at CDS, Strasbourg, France. DANIEL B. CATON WANDA C. BURNS Dark Sky Observatory Department of Physics and Astronomy Appalachian State University Boone, North Carolina 28608 U.S.A. References: Caton, D. B., 1989, Bull. A. A. S., 21, No. 1, 714 [BIBCODE 1989BAAS...21R.714C ] Caton, D. B., Hawkins, R. L., and Burns, W. C. 1989, Inf. Bull. Var. Stars, No. 3408 Ghedini, S., 1982, Software for Photometric Astronomy, Willman-Bell, Richmond, VA, p. 46 [BIBCODE 1982spa..book.....G ] Gimenez, A., 1985, Astrophys.J. 297, 405. [BIBCODE 1985ApJ...297..405G ] Gimenez, A. and Delgado, A., 1980, Inf. Bull. Var. Stars, No. 1815 Gimenez, A. and Margrave, T., 1982, Astron. J., 87, 1233 [BIBCODE 1982AJ.....87.1233G ] Hegedus, T., 1988, Bull. Inf. Centre Donnees Stellaires, 35, 15 [BIBCODE 1988BICDS..35...15H ] Kholopov, P. N., editor 1985-87, General Catalog of Variable Stars, Fourth Edition, Nauka Publishing, Moscow Kwee, K. and van Woerden, H., 1956, B.A.N., 12, 327 [BIBCODE 1956BAN....12..327K ] Maloney, F.P., Guinan, E.F., and Mukherjee, J., 1991, Astron. J., 102, 256 [BIBCODE 1991AJ....102..256M ] Todoran, I. and Roman, R., 1992, Inf. Bull. Var. Stars, No. 3819 [DATAFILE 2]