COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3176 Konkoly Observatory Budapest 13 April 1988 HU ISSN 0374-0676 IS TAU CASSIOPEIAE A VARIABLE STAR? The star tau Cassiopeiae (tau Cas, HD 223165, HR 9008, SAO 35763, K1 III, V= 4.87m) was observed at the University of Northern Iowa (UNI) Hillside Observatory during 1986 and 1987. We used a 0.4 meter Cassegrain telescope and a STARLIGHT-1 photon counting photometer with standard B and V filters. tau Cas has been used extensively as a comparison star for Rho Cassiopeiae variability studies. The American Association of Variable Star Observers has used Tau Cassiopeiae as a primary comparison star for Rho Cassiopeiae for a number of years. Tau Cas is listed in the New Catalogue of Suspected Variable Stars (Kholopov, 1982). Due to this suspected variability tau Cas was gradually dropped from the Rho Cassiopeiae observing program by the British Astronomical Association (Percy, 1985). Although Percy's work leads him to believe that tau Cas may not be a variable star. As a portion of a study done at UNI on rho Cassiopeiae, we believe that tau Cas does have a small degree of variability. HD 223173 (HR 9010, SAO 35761, K3 II, V = 5.51m, B-V = 1.65) was used as the comparison star. Table 1 lists the mean delta magnitudes obtained for tau Cas. Figures 1 and 2 are graphical representations of these data. [FIGURE 1] Figure 1 tau Cas Visual Delta Magnitudes Table 1 Tau Cas Visual and Blue Delta Magnitudes JD V error # JD B error # 2446670.616 -0.687 0.005 2 2446670.631 -1.136 0.004 2 2446671.663 -0.728 0.028 2 2446674.709 -1.127 0.009 2 2446674.591 -0.692 0.023 2 2446675.685 -1.081 0.017 2 2446675.665 -0.660 0.026 2 2446678.663 -1.126 0.006 2 2446678.642 -0.660 0.011 2 2446680.655 -1.121 0.009 2 2446680.638 -0.675 0.007 2 2446681.674 -1.113 0.006 2 2446681.658 -0.656 0.026 2 2446686.593 -1.107 0.021 2 2446686.573 -0.680 0.015 2 2446699.565 -1.118 0.005 2 2446697.658 -0.744 1 2446701.652 -1.143 0.021 2 2446699.547 -0.688 0.035 2 2446704.584 -1.110 0.047 2 2446701.622 -0.714 0.006 2 2446708.563 -1.154 0.008 2 2446701.720 -0.670 0.018 2 2446709.569 -1.170 0.034 2 2446704.544 -0.620 0.025 2 2446713.564 -1.116 0.019 2 2446705.625 -0.697 0.086 2 2446718.601 -1.135 0.005 2 2446708.546 -0.677 0.004 2 2446722.553 -1.146 0.018 2 2446708.621 -0.680 0.008 2 2446731.535 -1.140 0.000 2 2446709.550 -0.687 0.039 2 2446737.544 -1.131 0.019 2 2446711.540 -0.656 1 2446743.571 -1.116 0.026 2 2446713.545 -0.638 0.031 2 2446759.562 -1.130 0.008 2 2446718.585 -0.687 0.028 2 2446769.527 -1.130 0.008 2 2446720.536 -0.661 0.046 2 2446775.505 -1.119 0.004 2 2446722.530 -0.705 0.001 2 2446783.524 -1.121 0.044 2 2446731.516 -0.685 0.010 2 2446800.571 -1.166 0.066 2 2446737.527 -0.686 0.022 2 2446820.581 -1.128 0.003 3 2446740.684 -0.636 0.048 2 2446828.627 -1.135 0.010 3 2446743.548 -0.668 0.010 2 2446835.572 -1.138 0.007 3 2446749.538 -0.666 0.021 2 2446838.645 -1.138 0.010 3 2446759.542 -0.669 0.037 2 2446839.670 -1.175 0.010 3 2446769.546 -0.693 0.011 2 2446844.708 -1.135 0.018 3 2446775.523 -0.677 0.025 2 2446930.895 -1.152 0.008 3 2446783.542 -0.709 0.015 2 2446931.861 -1.126 0.004 3 2446800.600 -0.671 0.057 2 2446951.713 -1.152 0.001 3 2446814.566 -0.669 0.002 3 2446952.663 -1.157 0.008 3 2446820.568 -0.680 0.006 3 2446953.686 -1.169 0.009 3 2446828.615 -0.685 0.014 3 2446958.764 -1.137 0.003 3 2446833.587 -0.685 0.009 3 2446960.742 -1.123 0.012 3 2446835.564 -0.691 0.003 3 2446838.644 -0.667 0.023 3 2446839.662 -0.686 0.005 3 2446844.699 -0.687 0.012 3 2446930.884 -0.720 0.007 3 2446931.851 -0.682 0.004 3 2446951.723 -0.692 0.014 3 2446952.654 -0.727 0.009 3 2446953.674 -0.677 0.011 3 2446958.754 -0.674 0.008 3 2446960.729 -0.664 0.004 3 [FIGURE 2] Figure 2 tau Cas Blue Delta Magnitudes P. STEVEN LEIKER Hillside Observatory Department of Earth Science University of Northern Iowa Cedar Falls, IA 50614-0506 DARREL B. HOFF Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 References: Kholopov, P. N. (1982). New catalogue of suspected variable stars. Moscow: Publishing Office (Nauka). [BIBCODE 1982ncss.book.....K ] Percy, J. R. (1985). Tau Cas: not a variable star. Variable Star Observers, 14, (2), 52-54. [BIBCODE 1985JAVSO..14...52P ]