COMMISSION 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3802 Konkoly Observatory Budapest 5 November 1992 HU ISSN 0374 - 0676 THE VARIATION OF THE LIGHT CURVES OF AU Ser The binary AU Ser was observed visually and photographically by Soloviev (1951) and Huth (1964) respectively. The first photoelectric observations were performed by Binnendijk (1972). The light curves show different heights of the primary and secondary maximum and rather rapid variation in the shape. Kaluzny (1986) analysed Binnendijk's data and found this binary to be poor thermal contact system although the uniqueness of the solution was not sufficiently discussed. It is important to monitor such an interesting binary. Unfortunately, because AU Ser is rather faint, there is few photometric observation carried out for this system since 1970. We observed this star photoelectrically, using the 1-meter reflector of the Yunnan Observatory, China, on two nights, 9-11 April 1991. The coordinates (1950) of the binary, the comparison and the check star are 15h54m39s +22d24'.3, 15h55m01s +22d17'.5 and 15h54m33s +22d24'.9, respectively. A finder chart is given in Fig. 1 where 1, 2 and 3 represent the variable, the comparison and the check star. A total of 264 yellow (Table 1) and 264 blue (Table 2) observations were obtained. The probable error of a single observation was estimated to be +-0.015 mag. The moment of the primary minimum is JD 2448356.3364+-0.0003 which corresponds to phase of 0.93 according to Binnendijk's ephemeris Min. I = JD2440748.8592 + 0.38650124E. [FIGURE 1] Figure 1. Finder chart for AU Ser(1), the comparison(2) and the check star(3) The light curves are plotted in Figure 2 where zero point corrections of +1.538 for V light and +2.000 for B light were introduced so that the maximum of magnitude difference in V band is equal to zero. Figure 2 shows that the maximum following secondary minimum is 0.05 mag higher than the other one in contrast with the light curves obtained by Binnendijk in 1969 where the maximum following the primary minimum is 0.05 mag higher than the other. Regarding the displacement of the minimum time, we are not sure if it suggests the change of the period. Table 1. Yellow observations of AU Ser JD JD JD 244800+ DeltaV 244800+ DeltaV 244800+ DeltaV 356.1665 -1.183 356.2679 -1.450 356.3896 -1.356 356.1678 -1.212 356.2691 -1.429 356.3906 -1.357 356.1688 -1.214 356.2693 -1.438 356.3941 -1.387 356.1700 -1.239 356.2706 -1.420 356.3954 -1.406 356.1724 -1.237 356.2733 -1.412 356.4002 -1.406 356.1733 -1.256 356.2744 -1.417 356.4017 -1.415 356.1735 -1.251 356.2747 -1.428 357.1485 -1.223 356.1744 -1.274 356.2757 -1.409 357.1491 -1.223 356.1768 -1.307 356.2856 -1.349 357.1500 -1.226 356.1777 -1.313 356.2867 -1.332 357.1502 -1.241 356.1779 -1.318 356.2869 -1.327 357.1522 -1.247 356.1788 -1.327 356.2880 -1.331 357.1531 -1.247 356.1853 -1.387 356.2921 -1.284 357.1533 -1.247 356.1862 -1.402 356.2932 -1.280 357.1542 -1.254 356.1864 -1.390 356.2936 -1.282 357.1576 -1.296 356.1873 -1.404 356.2948 -1.262 357.1584 -1.318 356.1902 -1.427 356.3050 -1.173 357.1586 -1.312 356.1912 -1.439 356.3060 -1.155 357.1595 -1.323 356.1914 -1.434 356.3062 -1.157 357.1628 -1.326 356.1926 -1.437 356.3074 -1.132 357.1637 -1.332 356.2069 -1.502 356.3104 -1.038 357.1639 -1.328 356.2079 -1.507 356.3113 -1.042 357.1647 -1.333 356.2081 -1.499 356.3116 -1.021 357.1668 -1.373 356.2090 -1.510 356.3128 -1.019 357.1674 -1.377 356.2116 -1.504 356.3161 -0.961 357.1676 -1.380 356.2126 -1.528 356.3174 -0.937 357.1686 -1.393 356.2129 -1.531 356.3177 -0.931 357.1714 -1.366 356.2141 -1.520 356.3191 -0.918 357.1722 -1.378 356.2168 -1.520 356.3286 -0.724 357.1724 -1.385 356.2236 -1.535 356.3295 -0.717 357.1733 -1.373 356.2239 -1.528 356.3298 -0.685 357.1808 -1.418 356.2248 -1.541 356.3307 -0.683 357.1819 -1.406 356.2271 -1.524 356.3341 -0.630 357.1821 -1.404 356.2281 -1.535 356.3359 -0.624 357.1831 -1.395 356.2283 -1.533 356.3363 -0.634 357.1860 -1.434 356.2293 -1.535 356.3379 -0.631 357.1870 -1.434 356.2318 -1.534 356.3419 -0.657 357.1873 -1.447 356.2428 -1.520 356.3430 -0.670 357.1884 -1.447 356.2430 -1.524 356.3432 -0.672 357.1918 -1.464 356.2438 -1.533 356.3442 -0.687 357.1927 -1.448 356.2465 -1.522 356.3471 -0.734 357.1936 -1.476 356.2477 -1.514 356.3485 -0.752 357.1938 -1.473 356.2480 -1.515 356.3487 -0.769 357.2007 -1.474 356.2490 -1.507 356.3499 -0.772 357.2016 -1.481 356.2517 -1.496 356.3535 -0.868 357.2018 -1.487 356.2575 -1.500 356.3549 -0.888 357.2026 -1.486 356.2584 -1.495 356.3552 -0.906 357.2046 -1.491 356.2586 -1.511 356.3566 -0.923 357.2058 -1.509 356.2597 -1.492 356.3599 -0.980 357.2060 -1.513 356.2622 -1.468 356.3610 -1.010 357.2069 -1.494 356.2635 -1.469 356.3615 -1.016 357.2156 -1.492 356.2637 -1.462 356.3867 -1.321 357.2167 -1.511 356.2649 -1.460 356.3892 -1.349 357.2170 -1.507 JD JD 244800+ DeltaV 244800+ DeltaV 357.2179 -1.495 357.3088 -0.885 357.2212 -1.496 357.3122 -0.962 357.2221 -1.497 357.3136 -0.981 357.2224 -1.490 357.3139 -0.997 357.2233 -1.501 357.3152 -0.974 357.2254 -1.497 357.3179 -1.064 357.2265 -1.492 357.3191 -1.089 357.2307 -1.502 357.3194 -1.097 357.2317 -1.500 357.3229 -1.147 357.2320 -1.502 357.3256 -1.168 357.2333 -1.493 357.3265 -1.192 357.2360 -1.481 357.3267 -1.190 357.2370 -1.471 357.3275 -1.198 357.2372 -1.476 357.3341 -1.296 357.2381 -1.469 357.3349 -1.309 357.2406 -1.461 357.3352 -1.310 357.2415 -1.470 357.3396 -1.314 357.2417 -1.464 357.3407 -1.335 357.2427 -1.456 357.3409 -1.340 357.2496 -1.436 357.3418 -1.360 357.2506 -1.444 357.3476 -1.407 357.2508 -1.440 357.3478 -1.401 357.2548 -1.424 357.3487 -1.400 357.2550 -1.421 357.3522 -1.465 357.2559 -1.424 357.3539 -1.464 357.2586 -1.400 357.3542 -1.453 357.2595 -1.397 357.3566 -1.482 357.2598 -1.391 357.3579 -1.491 357.2611 -1.377 357.3582 -1.482 357.2641 -1.338 357.3592 -1.488 357.2650 -1.324 357.3685 -1.520 357.2653 -1.331 357.3693 -1.515 357.2662 -1.323 357.3696 -1.526 357.2685 -1.300 357.3704 -1.531 357.2696 -1.284 357.3731 -1.513 357.2699 -1.277 357.3739 -1.536 357.2707 -1.272 357.3741 -1.526 357.2740 -1.260 357.3749 -1.522 357.2749 -1.244 357.3862 -1.532 357.2751 -1.236 357.3870 -1.536 357.2759 -1.232 357.3872 -1.534 357.2828 -1.124 357.3882 -1.543 357.2841 -1.093 357.3916 -1.536 357.2846 -1.084 357.3924 -1.548 357.2862 -1.047 357.3997 -1.527 357.2924 -0.931 357.4005 -1.530 357.2926 -0.898 357.4007 -1.531 357.2937 -0.882 357.4017 -1.521 357.2996 -0.836 357.4101 -1.518 357.3007 -0.819 357.4109 -1.530 357.3010 -0.819 357.4111 -1.527 357.3063 -0.871 357.4119 -1.530 357.3074 -0.885 Table 2. Blue observations of AU Ser JD JD JD 244800+ DeltaB 244800+ DeltaB 244800+ DeltaB 356.1671 -1.303 356.2642 -1.578 356.3961 -1.506 356.1674 -1.291 356.2646 -1.581 356.3964 -1.526 356.1694 -1.348 356.2683 -1.553 356.4009 -1.514 356.1697 -1.346 356.2688 -1.539 356.4010 -1.517 356.1773 -1.428 356.2697 -1.533 356.4025 -1.537 356.1782 -1.427 356.2699 -1.520 356.4027 -1.535 356.1784 -1.448 356.2859 -1.427 356.4144 -1.634 356.1813 -1.485 356.2862 -1.428 356.4146 -1.641 356.1816 -1.478 356.2874 -1.416 357.1487 -1.344 356.1824 -1.492 356.2876 -1.411 357.1489 -1.311 356.1827 -1.482 356.2926 -1.378 357.1495 -1.353 356.1856 -1.518 356.2928 -1.382 357.1497 -1.353 356.1859 -1.517 356.2940 -1.359 357.1525 -1.337 356.1867 -1.522 356.2944 -1.359 357.1527 -1.347 356.1869 -1.530 356.3054 -1.262 357.1579 -1.373 356.1905 -1.573 356.3056 -1.243 357.1581 -1.376 356.1919 -1.577 356.3068 -1.242 357.1590 -1.404 356.1921 -1.571 356.3070 -1.226 357.1592 -1.410 356.2022 -1.620 356.3107 -1.145 357.1632 -1.467 356.2024 -1.617 356.3110 -1.145 357.1634 -1.458 356.2120 -1.646 356.3121 -1.133 357.1642 -1.461 356.2122 -1.662 356.3123 -1.124 357.1644 -1.465 356.2134 -1.655 356.3166 -1.042 357.1671 -1.481 356.2137 -1.651 356.3169 -1.041 357.1679 -1.503 356.2230 -1.681 356.3182 -1.012 357.1681 -1.499 356.2233 -1.682 356.3186 -0.994 357.1683 -1.497 356.2243 -1.686 356.3289 -0.776 357.1716 -1.484 356.2245 -1.697 356.3292 -0.760 357.1719 -1.490 356.2275 -1.674 356.3301 -0.740 357.1726 -1.483 356.2277 -1.684 356.3304 -0.748 357.1728 -1.480 356.2287 -1.681 356.3353 -0.677 357.1866 -1.543 356.2289 -1.676 356.3371 -0.680 357.1868 -1.542 356.2324 -1.667 356.3373 -0.691 357.1875 -1.572 356.2328 -1.668 356.3424 -0.723 357.1877 -1.573 356.2341 -1.686 356.3426 -0.733 357.1921 -1.579 356.2343 -1.680 356.3436 -0.750 357.1924 -1.559 356.2423 -1.666 356.3438 -0.752 357.1931 -1.576 356.2425 -1.653 356.3476 -0.818 357.1933 -1.567 356.2434 -1.652 356.3480 -0.836 357.2010 -1.606 356.2436 -1.652 356.3491 -0.851 357.2012 -1.617 356.2468 -1.646 356.3494 -0.871 357.2021 -1.613 356.2473 -1.630 356.3540 -0.987 357.2023 -1.610 356.2483 -1.638 356.3543 -0.990 357.2051 -1.637 356.2486 -1.631 356.3555 -1.013 357.2066 -1.635 356.2522 -1.632 356.3558 -1.023 357.2096 -1.617 356.2526 -1.621 356.3604 -1.081 357.2102 -1.618 356.2535 -1.615 356.3607 -1.090 357.2115 -1.612 356.2537 -1.610 356.3619 -1.096 357.2118 -1.610 356.2578 -1.607 356.3621 -1.087 357.2160 -1.649 356.2581 -1.604 356.3885 -1.471 357.2175 -1.640 356.2592 -1.614 356.3888 -1.474 357.2216 -1.619 356.2627 -1.590 356.3946 -1.496 357.2218 -1.624 356.2629 -1.585 356.3949 -1.498 357.2227 -1.631 JD JD 244800+ DeltaB 244800+ DeltaB 357.2229 -1.632 357.3143 -1.078 357.2257 -1.616 357.3146 -1.060 357.2259 -1.612 357.3184 -1.159 357.2269 -1.606 357.3186 -1.178 357.2271 -1.600 357.3197 -1.191 357.2314 -1.623 357.3199 -1.205 357.2326 -1.605 357.3260 -1.280 357.2363 -1.589 357.3262 -1.300 357.2365 -1.589 357.3270 -1.296 357.2375 -1.591 357.3272 -1.292 357.2377 -1.579 357.3301 -1.340 357.2409 -1.584 357.3303 -1.361 357.2411 -1.598 357.3312 -1.363 357.2420 -1.598 357.3314 -1.360 357.2422 -1.589 357.3344 -1.437 357.2542 -1.550 357.3346 -1.445 357.2544 -1.549 357.3399 -1.458 357.2553 -1.542 357.3402 -1.471 357.2556 -1.536 357.3413 -1.491 357.2590 -1.532 357.3415 -1.509 357.2592 -1.519 357.3451 -1.507 357.2606 -1.515 357.3455 -1.503 357.2608 -1.508 357.3582 -1.532 357.2645 -1.487 357.3484 -1.522 357.2647 -1.482 357.3514 -1.572 357.2656 -1.474 357.3518 -1.582 357.2658 -1.475 357.3530 -1.552 357.2688 -1.410 357.3535 -1.576 357.2693 -1.409 357.3572 -1.614 357.2702 -1.395 357.3576 -1.617 357.2704 -1.396 357.3589 -1.622 357.2743 -1.373 357.3591 -1.623 357.2746 -1.365 357.3699 -1.624 357.2754 -1.337 357.3701 -1.636 357.2756 -1.339 357.3733 -1.674 357.2833 -1.214 357.3736 -1.671 357.2835 -1.189 357.3744 -1.684 357.2855 -1.145 357.3746 -1.673 357.2857 -1.133 357.3823 -1.680 357.2918 -1.062 357.3825 -1.688 357.2920 -1.059 357.3865 -1.662 357.2931 -1.028 357.3867 -1.670 357.2934 -1.025 357.3875 -1.669 357.3002 -1.885 357.3878 -1.675 357.3004 -1.891 357.3909 -1.673 357.3013 -1.908 357.3911 -1.676 357.3016 -1.922 357.3919 -1.680 357.3068 -1.962 357.3921 -1.706 357.3070 -1.967 357.4000 -1.686 357.3080 -1.972 357.4002 -1.678 357.3082 -1.980 357.4012 -1.680 357.3130 -1.075 357.4014 -1.685 357.3133 -1.071 Note that the previous minimum times listed by Binnendijk (1972) seem to indicate no significant variation in period occurred from 1936 to 1970. It is necessary to monitor this object in different wavelengths. We will continue the photometry for it and a spectroscopic observation has been planned. [FIGURE 2] Figure 2. The light and color curves of AU Ser LI Zong-yun 1,2,3 ZHAN Zhou-sheng 2 LI Yu-lan 2 1, Optical Astronomy Lab. Chinese Academy of Science, Beijing 100080, China 2, Yunnan Observatory, Kuming 650011, China 3, Department of Astronomy Nanjing University, Nanjing 210008, China References: Binnendijk, L., 1972, Astron. J. 77, 603. [BIBCODE 1972AJ.....77..603B ] Huth, H., 1964, Mitt. Sonneberg 2, No. 5, 126. Kaluzny, J., 1986, Acta Astronomica 36, 113. [BIBCODE 1986AcA....36..113K ] Soloviev, A. V., 1951, Variable Stars 8, 65.