COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1111 Konkoly Observatory Budapest 1976 March 7 UBV PHOTOELECTRIC MINIMUM OF AO VELORUM AO Velorum is an eclipsing variable star with large apsidal motion and it has been listed by Batten (1973) among stars deserving observational attention. AO Velorum or HD 68826 was observed during 5 nights with 60cm Lowel-Perth reflector at Perth Observatory in December 1974 and January 1975. The integrating photometer, described by Millis et al. (1974), was used with the standard UBV filters and EMI 6526S photomultiplier. During the observation the digital display of the photometer and digital display of universal time was written down. The standard procedure, comparison star - variable - comparison, etc., was used, the variable star being occasionally replaced by a check star. The integration time was 10 seconds and each measurement represents the average of at least 3 integrations. The time was recorded at the beginning of each set of readings and later reduced to the middle of the measuring interval (ranging from 30 to 50 seconds). The brightness of the sky background was read (3 readings) after the measurement with each filter. The flanking apertures were used for sky measurements: HD 68557 served as comparison star. The reduced data in Table I represents time in heliocentric Julian Days and observed differential magnitudes in the sense variable star minus comparison star, linearly interpolated for the time of the measurement of the variable. The reduction of measured values was performed with the HP 1900 desk calculator (with extended memory HP 9101A) and both the measured values and the reduced data were plotted simultaneously on the HP 9125B calculator plotter. More details concerning the evaluation of the measurements may be found in a previous paper (Kviz, 1975). Fig. 1 is direct output from the plotter. The time of the minimum was computed according to Kwee and Van Woerden's (1956) method for the interval JD hel 2442424.15 - 2442424.28. The time of the minimum and the respective mean errors of the measurements with individual filters are in Table II. I wish to express my appreciation of the help to the staff of Perth Observatory during my stay there. For assistance during observations I thank Mr. A Verveer and my wife J. Kvizova. [FIGURE 1] Z. KVIZ University of New South Wales Broken Hill Division Broken Hill. N.S.W. 2880 AUSTRALIA. References: Batten, A.H. 1973, Binary and Multiple Systems of Stars, p. 138. [BIBCODE 1973bmss.book.....B ] Kviz, Z. 1975, Proc. Astr. Soc. Australia 2, 351. [BIBCODE 1975PASAu...2..351K ] Kwee, K.K. and van Woerden, H. 1956, Bull. Astr. Inst. Neth. 12, 327. [BIBCODE 1956BAN....12..327K ] Millis, R.L. et al. 1974, Icarus 23, 425. [BIBCODE 1974Icar...23..425M ] Table 1 UBV Photoelectric measurements of AO Velorum DeltaV DeltaB DeltaU JD_hel 2440000. + 2408.1017 +0.495 2408.1030 +0.400 2408.1043 -0.030 1114 +0.484 1126 +0.392 1142 -0.096 1298 +0.504 1310 +0.416 1321 -0.029 1389 +0.504 1402 +0.391 1415 -0.090 1487 +0.500 1500 +0.402 1511 -0.039 1578 +0.486 1590 +0.406 1602 -0.036 1683 +0.505 1695 +0.384 1708 -0.027 1776 +0.481 1790 +0.388 1803 -0.009 1897 +0.486 1908 +0.396 1920 -0.063 1992 +0.533 2007 +0.406 2020 -0.020 2102 +0.490 2116 +0.398 2129 -0.112 2207 +0.490 2223 +0.404 2236 -0.034 2310 +0.495 2322 +0.403 2334 -0.093 2407 +0.485 2419 +0.401 2435 -0.067 2507 +0.498 2521 +0.398 2533 -0.035 2606 +0.496 2620 +0.409 2632 +0.008 2711 +0.501 2727 +0.406 2740 +0.014 2814 +0.513 2829 +0.420 2842 -0.008 2918 +0.538 2932 +0.445 2948 +0.059 3032 +0.571 3045 +0.494 3057 +0.057 3140 +0.624 3154 +0.544 3166 +0.125 3239 +0.666 3252 +0.593 3262 +0.162 3335 +0.730 3346 +0.649 3357 +0.256 2410.0475 +0.498 2410.0489 +0.415 2410.0502 +0.038 0563 +0.494 0576 +0.413 0589 -0.024 0652 +0.496 0666 +0.411 0679 -0.034 0834 +0.504 0848 +0.407 0860 -0.057 0921 +0.505 0932 +0.412 0945 -0.061 2216.0270 +0.487 2416.0283 +0.395 2416.0297 -0.036 0365 +0.529 0376 +0.392 0389 -0.043 0594 +0.503 0555 +0.400 0566 -0.017 0627 +0.488 0639 +0.400 0650 -0.020 2423.1892 +0.485 2423.1909 +0.382 2423.1926 -0.114 2027 +0.498 2043 +0.390 2057 +0.020 2147 +0.477 2161 +0.394 2177 -0.042 2273 +0.498 2286 +0.408 2303 -0.020 2415 +0.498 2430 +0.400 2444 +0.052 2528 +0.488 2541 +0.396 2554 -0.097 2654 +0.510 2668 +0.404 2683 -0.082 2782 +0.500 2800 +0.399 2817 0.000 2918 +0.501 2933 +0.406 2946 +0.016 3033 +0.507 3050 +0.403 3064 -0.011 3153 +0.510 3167 +0.403 3183 -0.018 3269 +0.505 3284 +0.402 3701 +0.043 Primary Minimum DeltaV DeltaB DeltaU 2424.0475 +0.492 2424.0489 +0.405 2424.0509 +0.050 0580 +0.508 0595 +0.396 0610 -0.009 0787 +0.477 0801 +0.410 0817 -0.040 1004 +0.502 1021 +0.401 1036 -0.068 1461 +0.578 1475 +0.495 1488 +0.019 1564 +0.624 1577 +0.519 1590 +0.171 1666 +0.657 1679 +0.573 1691 +0.188 1759 +0.707 1771 +0.634 1786 +0.276 1855 +0.775 1869 +0.692 1882 +0.304 1950 +0.850 1962 +0.771 1976 +0.376 2048 +0.903 2059 +0.827 2071 +0.406 2131 +0.945 2141 +0.871 2152 +0.514 2211 +0.954 2221 +0.857 2232 +0.464 2296 +0.892 2307 +0.797 2319 +0.468 2380 +0.841 2391 +0.745 2402 +0.395 2465 +0.771 2476 +0.684 2488 +0.352 2549 +0.715 2562 +0.619 2575 +0.299 2643 +0.665 2653 +0.570 2664 +0.146 2741 +0.615 2754 +0.527 2766 +0.044 2838 +0.582 2850 +0.483 2862 +0.018 2927 +0.546 2940 +0.448 2955 +0.011 3026 +0.500 3038 +0.422 3053 +0.011 3124 +0.506 3138 +0.900 3152 -0.053 3223 +0.488 3235 +0.397 3250 0.000 3317 +0.499 3329 +0.399 3341 -0.078 3405 +0.491 3416 +0.402 3428 -0.025 Table II Time of Minimum Filter T min V 2424.2159 +- .0003 B .2162 +- .0003 V .217 +- .002