COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3004 Konkoly Observatory Budapest 25 March 1987 HU ISSN 0374-0676 OBSERVATIONS AND A TIME OF MINIMUM OF TV Cet TV Cet (BD +02d 502), is one of the eccentric-orbit eclipsing binary systems suggested by Giminez and Delgado (1980), and by Giminez (1985), as candidates for possible observation of general-relativistic apsidal motion. We have observed a secondary eclipse of TV Cet on the night of 1986 September 13-14 (JD 2446687), and have computed a time of minimum. The observations were made with the 46-cm reflector at Appalachian State University's Dark Sky Observatory. The photometer is a Kitt Peak National Observatory single-channel design employing a thermoelectrically cooled EMI 9865QB photomultiplier tube with matching UBVR filters. An Astronomical Time Mechanisms Model 240V amplifier provides a voltage-to- frequency output that is integrated by a microcomputer. The observations were made through the R filter only, to optimize the signal-to-noise ratio, since the sky was illuminated by a nearly full moon. The observations have not been transformed to Johnson R, since they were only intended for timing analysis. In order to maximize the number of data points, no additional filters were used. The comparison star used was BD +01d 566, located about 20 arc-minutes to the south of TV Cet. The star BD +02d 500 was used as a check star. The variable and comparison were alternately observed for 10-second integration periods. The observations (V/C intensity ratio) are tabulated in Table I and plotted in Figure 1. The time of minimum light was Table I. Observations of TV Cet Hel. J.D V/C Hel. J.D V/C -2446687 -2446687 .75396 1.136 .81427 0.966 .75581 1.128 .81565 0.967 .75747 1.122 .81747 0.970 .76007 1.132 .81865 0.972 .76334 1.114 .81978 0.968 .76511 1.104 .82166 0.993 .76783 1.090 .82291 0.983 .77000 1.089 .82456 0.986 .77281 1.067 .82683 0.990 .77553 1.051 .83271 1.017 .77788 1.037 .83482 1.009 .77977 1.030 .83657 1.021 .78179 1.019 .83814 1.034 .78564 1.010 .84091 1.043 .78762 0.997 .84346 1.050 .79013 0.993 .84574 1.051 .79373 0.992 .84826 1.047 .79738 0.983 .85075 1.073 .79931 0.974 .85292 1.084 .80351 0.961 .85524 1.114 .80611 0.969 .85819 1.111 .80732 0.966 .86211 1.128 .80769 0.972 .86484 1.132 .81126 0.974 .86626 1.147 .81292 0.966 .86776 1.163 [FIGURE 1] Figure 1. Secondary eclipse of TV Cet calculated using a quadratic least-squares fit, using only the data found in the bottom 0.2 magnitudes of the eclipse. This follows the suggestion of Andersen and Giminez (1985), that asymmetries in the eclipse curve can cause errors if too much of the eclipse width is used. The same data were also analyzed using the method of Kwee and van Woerden (1956), using a program written by Ghedini (1982). The two methods yielded results that agreed within the observational errors. The resulting time of minimum is Min II = HJD 2446687.8101 +/-.0093 where the error is the mean error computed from the errors in the quadratic coefficients. Using the elements of Jorgensen (1979) places this secondary eclipse at phase 0.498. This may be compared to the light curve solution of Popper and Etzel (1981), which shows secondary minimum at phase 0.494 during 1972-73 (using the same elements). We gratefully acknowledge the assistance of F. B. Wood and G. Fitzgibbons in providing reference material from the University of Florida Card Catalogue of Eclipsing Binaries. DANIEL B. CATON R. LEE HAWKINS Department of Physics and Astronomy Appalachian State University Boone, North Carolina 28608 U.S.A. References: Andersen, J., and Gimenez, A. (1985). Astron.Astrophys. 145, 206. [BIBCODE 1985A&A...145..206A ] 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 ] Giminez, A. and Delgado, A. (1980), IAU Inf. Bull. Var. Stars, No. 1815. Jorgensen, H. (1979), Astron.J. 72, 356. [BIBCODE 1979A&A....72..356J ] Kwee, K. and van Woerden, H. (1956). B.A.N. 12, 327. [BIBCODE 1956BAN....12..327K ] Popper D., and Etzel, P. (1981). Astron.J. 86, 102. [BIBCODE 1981AJ.....86..102P ]