COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1547 Konkoly Observatory Budapest 1979 February 12 THE PHOTOELECTRIC MINIMA AND THE LIGHT CURVE OF THE ECLIPSING BINARY HU TAURI (BV 312) The eclipsing nature of HU Tau was first announced by Strohmeier and Knigge (1960). Strohmeier (1963) has given the light elements as JD=24256.41+2.056297d E (1) In GCVS's second supplement, a new set of light elements is given as JD=42412.256+2.056302d E (2) The spectroscopic orbital elements of the system were obtained by Mammano, Mannino and Margoni (1967), The have classified the spectral type of primary component as B9V. The system shows a single line spectrum. So far, no photoelectric light curve of HU Tau has been obtained. During the period from October, 1978 to November, 1978 the eclipsing binary HU Tau was observed photoelectrically with the 48 cm reflector, attached with an unrefrigerated 1P21 phototube, at Ege University Observatory and the light curve of the system was secured in two colours B and V. BD+19d742 and BD+19d740 were used as comparison and check stars, respectively. No variation in the light of comparison star was detected. The light curve and the colour variation are shown in Figure 1 and 2, respectively. The times of minima obtained during the observations made are shown in Table I. The O-C values were calculated with the help of Equation (2). Table I ------------------------------------------- JD (Hel) O-C E Minimum ------------------------------------------- 2443833.3662 +0.0055 691 primary 43834.3967 0.0079 secondary 43835.4228 0.0058 692 primary 43837.4797 0.0064 693 primary ------------------------------------------- [FIGURE 1] [FIGURE 2] The times of minima which have been obtained so far by other observers are listed in Table 2. The O-C values are computed again from Equation (2). The O-C values were plotted against E and are shown in Figure 3. Table II ------------------------------------- JD(Hel.) E O-C Ref. ------------------------------------- 2437925.609 -2182 +0.004 1 958.492 -2166 -0.014 1 958.494 -2166 -0.012 1 958.501 -2166 -0.005 1 958.509 -2166 +0.003 1 38770.754 -1771 +0.009 2 805.696 -1754 -0.006 2 39169.664 -1577 -0.004 3 194.337 -1565 -0.006 4 194.338 -1565 -0.005 5 198.458 -1563 +0.002 6 492.501 -1420 -0.006 5 40985.368 -694 -0.014 7 41244.476 -568 0 8 248.595 -566 +0.006 7 314.398 -534 +0.007 8 688.637 -352 -0,001 7 717.424 -338 -0.002 7 42052.615 -175 +0.012 5 375.454 - 18 +0.011 9 404.244 - 4 +0.013 9 408.343 - 2 -0.004 9 410.391 - 1 -0.009 9 412.452 0 -0.004 9 412.459 0 +0.003 9 412.462 0 +0.006 9 414.514 1 +0.002 9 445.360 16 +0.003 10 445.362 16 +0.005 10 447.409 17 -0.004 10 449.464 18 -0.005 10 449.476 18 +0.007 10 451.508 19 -0.018 10 739.410 159 +0.002 11 774.357 176 -0.008 12 774.361 176 -0.004 13 776.442 177 +0.021 13 786.715 182 +0.012 14 807.274 192 +0.008 15 43080.750 325 -0.004 16 105.427 337 -0.003 17 138.329 353 -0.002 17 138.341 353 +0.011 17 212.352 389 -0.005 18 212.369 389 +0.012 18 504.342 531 -0.010 19 508.450 533 -0.015 19 576.301 566 -0.022 19 2443578.353 567 -0.026 19 578.360 567 -0.019 19 578.363 567 -0.016 20 578.365 567 -0.014 19 578.366 567 -0.013 19 578.373 567 -0.006 19 732.597 642 -0.005 20 ------------------------------------ 1. Dueball, J. and Lehmann, R.B., 1965, A.N. 288, 167 2. Robinson, L.J., 1965, I.B.V.S., No. 111 3. Robinson, L.J., 1967, I.B.V.S., No. 180 4. Braune, W., Hubscher, J. and Mundry, E., 1970, A.N., 292, 185 5. Baldwin, M.E., 1977, J.A.A.V.S.O., 5, 24 6. Robinson, L.J., 1966, I.B.V.S., No. 154 7. Baldwin, M.E., 1977, J.A.A.V.S.O., 5, 84 8. B.B.S.A.G. Bulletin, 2, 1973 9. B.B.S.A.G. Bulletin, 20, 1975 10. B.B.S.A.G. Bulletin, 21, 1975 11. B.B.S.A.G. Bulletin, 26, 1976 12. B.B.S.A.G. Bulletin, 25, 1976 13. B.B.S.A.G. Bulletin, 27, 1976 14. Mallama, A.P. Skillman, D.R., Pinto, P.A. and Krobusek, B.A., 1977, I.B.V.S. No. 1249 15. B.B.S.A.G. Bulletin 34 16. Stephan, C.P., 1977, I.B.V.S., No. 1350 17. B.B.S.A.G. Bulletin, 32, 1977 18. B.B.S.A.G. Bulletin, 33, 1977 19. B.B.S.A.G. Bulletin, 37, 1978 20. B.B.S.A.G. Bulletin, 38, 1978 [FIGURE 3] Since, the times of minima listed in Table II were all obtained visually, as is seen from Figure 3, the O-C values show a great scatter along the line corresponding to O-C=0. An attempt has been made to improve the values of epoch, To, and period, P, by representation of points with a straight line. However, this failed because the correlation coefficient turned out to be too small due to the great scattering of the points. The analysis of the light curve is in progress. O. TUMER and M. KURUTAC Ege University Observatory Bornova - Izmir Turkey References: 1. Strohmeier, W., Knigge,R., Veroff. Bamberg Bd. V, 5, 1960 2. Strohmeier, W., Sky and Tel. 26, 264, 1963 [BIBCODE 1963S&T....26..264S ] 3. Mammano, A., Mannino, G. and Margoni, R., Mem.Soc.Ast.Italiana vol. 38, fasc. 3, 1967 [BIBCODE 1967MmSAI..38..459M ]