COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 4039 Konkoly Observatory Budapest 6 June 1994 HU ISSN 0374 - 0676 TIMES OF LIGHT MAXIMUM OF VZ CANCRI: 1994 SEASON^1 In a recent paper Arellano Ferro et al. (1994) studied the period variations of the delta Scuti star VZ Cnc and demonstrated that the period has not been steadily increasing as previously believed. The O - C residuals for the last 50 years, before and after being corrected from the beat period effects, show a structure that admits several interpretations: a slopping straight line which implies that the period needs to be revised, two abrupt period changes and, a sinusoidal variation. These authors have speculated that a sinusoidal variation might be produced by light-time effects in a binary system. Whether the sinusoidal appearance of the O - C residuals will persist in the future, other abrupt period changes will occur, or simply a period revision is needed, will be learned from the systematic obtention of times of maximum light in the years to come. During March and April 1994 we obtained differential photometry of VZ Cnc through the V filter using the stars BD+10d1818 and BD+10d1816 as comparison and check stars respectively. The observations were obtained with an Optec SSP-5A photoelectric photometer attached to the 0.57m telescope of the La Luz Observatory of the University of Guanajuato. We report nine observed times of maximum light and the corresponding O - C values in Table 1. We have calculated the O - C residuals using the ephemeris: T_max = HJD2431550.71 + 0.17836376E, and then (O - C) = T_max(obs) - T_max. Since only one more seasons will add very little to the understanding of the period variations of VZ Cnc already discussed by Arellano Ferro et al. (1994), we shall not carry our present discussion any further. However, we emphasize that yearly measurements of times of maximum light of VZ Cnc will contribute substantially to the understanding of the periodic nature of this star. In order to study overall drifts of the light curve and not only the moments of maximum brightness, future observers are encouraged to publish their full sets of observations. In Table 2 we report the V magnitude differences VZ Cnc -BD+10d1818 for our 1994 season. 1 Based on observations obtained at the La Luz Observatory of the University of Guanajuato, Mexico. Table 1. Times of light maximum of VZ Cnc in 1994 HJD O - C HJD O - C (244 9400.+) (days) (2449400.+) (days) 17.767 +0.0024 28.638 -0.0068 18.651 -0.0054 33.637 -0.0014 19.733 +0.0064 40.600 +0.0049 20.615 -0.0034 41.661 -0.0043 20.790 -0.0071: Table 2. Differential V photometry VZ Cnc - BD+10d1818 in 1994. HJD DeltaV HJD DeltaV HJD DeltaV HJD DeltaV HJD DeltaV 2449400.+ mag. 2449400.+ mag. 2449400.+ mag. 2449400.+ mag. 2449400.+ mag. 12.6332 1.058 12.8012 1.134 15.7878 0.859 17.6886 1.385 17.8095 1.190 12.6458 1.209 12.8049 1.186 15.7913 0.926 17.6911 1.400 17.8129 1.214 12.6428 1.179 12.8083 1.183 15.7947 0.939 17.6931 1.404 17.8168 1.230 12.6534 1.231 12.8123 1.178 15.7966 0.934 17.6955 1.405 17.8208 1.237 12.6501 1.214 12.8160 1.193 15.7988 0.936 17.6977 1.412 17.8236 1.242 12.6593 1.275 12.8201 1.222 15.8012 0.958 17.7003 1.416 17.8279 1.264 12.6565 1.258 12.8245 1.253 15.8038 0.966 17.7038 1.416 17.8309 1.287 12.6677 1.310 12.8287 1.273 15.8063 1.003 17.7060 1.418 17.8333 1.299 12.6632 1.291 12.8322 1.288 15.8089 0.947 17.7088 1.433 12.6739 1.322 12.8346 1.298 17.7110 1.450 18.6124 1.378 12.6711 1.314 12.8392 1.316 17.6003 0.913 17.7134 1.449 18.6192 1.366 12.6802 1.375 12.8424 1.325 17.6032 0.925 17.7172 1.448 18.6253 1.271 12.6768 1.364 17.6065 0.934 17.7199 1.442 18.6287 1.209 12.6856 1.378 15.7095 1.349 17.6105 0.958 17.7234 1.431 18.6343 1.104 12.6831 1.374 15.7128 1.340 17.6133 0.991 17.7285 1.376 18.6380 1.053 12.6922 1.377 15.7162 1.350 17.6162 1.006 17.7319 1.346 18.6415 1.011 12.6888 1.373 15.7194 1.383 17.6197 1.011 17.7352 1.300 18.6458 0.948 12.6986 1.405 15.7233 1.390 17.6222 1.028 17.7385 1.247 18.6533 0.952 12.6956 1.398 15.7258 1.376 17.6260 1.060 17.7429 1.171 18.6566 0.952 12.7024 1.413 15.7289 1.353 17.6292 1.087 17.7452 1.120 18.6602 0.988 12.7003 1.409 15.7321 1.349 17.6330 1.117 17.7482 1.028 18.6638 1.020 12.7078 1.412 15.7363 1.374 17.6367 1.147 17.7509 0.967 18.6726 1.078 12.7052 1.414 15.7388 1.369 17.6402 1.163 17.7535 0.873 18.6756 1.103 12.7131 1.415 15.7415 1.363 17.6438 1.186 17.7555 0.803 18.7229 1.269 12.7108 1.405 15.7444 1.371 17.6475 1.212 17.7579 0.782 18.7290 1.301 12.7188 1.421 15.7471 1.366 17.6505 1.234 17.7601 0.760 18.7324 1.304 12.7158 1.421 15.7495 1.370 17.6533 1.254 17.7640 0.771 18.7354 1.297 12.7245 1.432 15.7518 1.368 17.6558 1.260 17.7668 0.771 18.7397 1.303 12.7219 1.443 15.7543 1.353 17.6588 1.275 17.7693 0.794 18.7504 1.315 12.7299 1.381 15.7563 1.351 17.6623 1.307 17.7720 0.821 18.7527 1.316 12.7270 1.422 15.7594 1.364 17.6648 1.322 17.7747 0.850 18.7558 1.317 12.7304 1.394 15.7621 1.362 17.6668 1.327 17.7790 0.900 18.7579 1.320 12.7330 1.393 15.7647 1.321 17.6691 1.329 17.7819 0.941 18.7606 1.325 12.7362 1.358 15.7671 1.264 17.6720 1.333 17.7848 0.974 18.7632 1.332 12.7394 1.298 15.7699 1.228 17.6748 1.340 17.7879 1.004 18.7655 1.338 12.7838 0.899 15.7722 1.221 17.6770 1.349 17.7913 1.036 18.7677 1.341 12.7879 0.957 15.7754 1.157 17.6793 1.353 17.7947 1.063 18.7715 1.350 12.7911 1.004 15.7775 1.095 17.6816 1.364 17.7992 1.111 18.7741 1.364 12.7947 1.057 15.7797 1.047 17.6839 1.379 17.8026 1.145 18.7779 1.380 12.7973 1.085 15.7833 0.903 17.6863 1.380 17.8063 1.172 18.7811 1.378 18.7847 1.370 19.7291 0.922 20.6741 1.246 28.6040 1.370 33.6344 0.857 18.7868 1.371 19.7316 0.903 20.6765 1.255 28.6065 1.350 33.6379 0.881 18.7924 1.379 19.7337 0.906 20.6786 1.269 28.6092 1.329 33.6398 0.898 18.7952 1.359 19.7367 0.908 20.6841 1.302 28.6116 1.312 33.6428 0.925 18.7974 1.353 19.7410 0.913 20.6877 1.325 28.6136 1.286 33.6460 0.950 18.8009 1.301 19.7462 0.932 20.6901 1.318 28.6163 1.251 33.6504 0.991 18.8030 1.321 19.7511 0.966 20.6920 1.314 28.6187 1.198 33.6531 1.012 18.8060 1.297 19.7542 0.980 20.6947 1.330 28.6210 1.152 18.8099 1.274 19.7590 1.015 20.6976 1.337 28.6242 1.079 40.6563 1.053 19.7623 1.042 20.6999 1.340 28.6281 0.986 40.6589 1.086 19.5966 1.175 19.7694 1.086 20.7026 1.352 28.6342 0.915 40.6636 1.120 19.5990 1.173 19.7764 1.128 20.7050 1.362 28.6374 0.883 40.6698 1.170 19.6023 1.176 19.7791 1.151 20.7073 1.361 28.6456 0.921 40.6824 1.251 19.6047 1.179 19.7816 1.168 20.7098 1.358 28.6480 0.929 40.6854 1.274 19.6073 1.190 19.7850 1.178 20.7131 1.372 28.6551 1.005 40.5981 0.797 19:6102 1.202 19.7885 1.202 20.7166 1.381 28.6572 1.027 49.6005 0.791 19.6120 1.205 19.7909 1.225 20.7249 1.361 28.6606 1.054 40.6037 0.814 19.6140 1.211 19.1937 1.238 20.7223 1.368 28.6645 1.085 40.6066 0.828 19.6230 1.252 19.7967 1.251 20.7309 1.380 28.6679 1.116 40.6098 0.847 19.6299 1.276 19.7998 1.277 20.7278 1.377 28.6708 1.146 40.6121 0.871 19.6439 1.335 19.8036 1.297 20.7401 1.400 28.6739 1.173 40.6156 0.929 19.6460 1.345 19.8063 1.310 20.7362 1.405 28.6768 1.188 40.6178 0.957 19.6485 1.349 19.8106 1.335 20.7473 1.388 28.6798 1.192 40.6236 1.013 19.6507 1.349 19.8129 1.330 20.7440 1.395 28.6822 1.205 40.6261 1.033 19.6534 1.380 19.8157 1.311 20.7542 1.365 28.6853 1.225 40.6284 1.050 19.6565 1.411 19.8183 1.323 20.7508 1.376 28.6879 1.239 40.6305 1.068 19.6590 1.398 20.7615 1.331 28.6906 1.249 40.6342 1.112 19.6625 1.378 20.6065 0.911 20.7585 1.382 28.6934 1.249 40.6366 1.141 19.6651 1.399 20.6082 0.856 20.7685 1.217 28.6963 1.250 40.6417 1.173 19.6675 1.420 20.6106 0.813 20.7652 1.272 28.6989 1.255 40.6444 1.182 19.6701 1.413 20.6126 0.769 20.7733 1.142 28.7018 1.260 40.6472 1.194 19.6720 1.413 20.6152 0.765 20.7707 1.193 28.7009 1.260 40.6553 1.256 19.6761 1.413 20.6178 0.765 20.7783 1.033 28.7077 1.261 40.6526 1.247 19.6803 1.415 20.6207 0.783 20.7759 1.081 28.7106 1.274 40.6643 1.297 19.6832 1.422 20.6236 0.804 20.7833 0.964 28.7128 1.287 40.6624 1.285 19.6881 1.422 20.6261 0.837 20.7809 0.972 28.7158 1.271 40.6718 1.325 19.6918 1.396 20.6279 0.858 20.7888 0.852 28.7201 1.256 40.6682 1.321 19.6958 1.363 20.6306 0.879 20.7864 0.855 28.7243 1.293 40.6798 1.362 19.6986 1.344 20.6328 0.900 20.7943 0.946 28.7273 1.325 40.6770 1.354 19.7011 1.329 20.6358 0.931 20.7918 0.928 28.7304 1.338 40.6877 1.370 19.7043 1.282 20.6378 0.953 20.7996 0.965 28.7344 1.329 40.6835 1.362 19.7064 1.247 20.6411 0.993 20.7975 0.938 28.7380 1.324 40.6945 1.381 19.7088 1.212 20.6449 1.034 20.8046 1.010 40.6910 1.374 19.7112 1.183 20.6500 1.083 20.8026 0.997 33.6163 1.140 40.7006 1.400 19.7133 1.151 20.6536 1.118 20.8098 1.059 33.6189 1.081 40.6981 1.392 19.7161 1.105 20.6566 1.144 20.8074 1.029 33.6217 1.004 40.7077 1.412 19.7188 1.057 20.6601 1.174 20.8157 1.099 33.6233 0.962 40.7036 1.407 19.7211 1.020 20.6653 1.211 33.6264 0.929 40.7310 1.384 19.7241 0.973 20.6684 1.219 28.5987 1.392 33.6291 0.893 40.7419 1.310 19.7264 0.940 20.6715 1.230 28.6013 1.386 33.6322 0.872 40.7387 1.363 40.7536 1.062 41.6624 1.029 50.5979 0.863 50.6776 1.325 68.6464 1.208 40.7462 1.239 41.6655 1.043 50.6005 0.875 50.6802 1.340 68.6499 1.218 40.7634 0.828 41.6676 1.053 50.6031 0.886 50.6832 1.380 68.6563 1.247 41.6719 1.062 50.6060 0.929 50.6855 1.384 41.5943 1.355 41.6751 1.077 50.6086 0.951 50.6887 1.395 69.6002 1.361 41.5970 1.359 41.6778 1.097 50.6117 0.973 50.6911 1.407 69.6022 1.367 41.6002 1.360 41.6816 1.115 50.6141 0.996 50.6941 1.392 69.6048 1.371 41.6041 1.370 41.6843 1.123 50.6170 0.995 50.6962 1.379 69.6074 1.365 41.6088 1.379 41.6868 1.139 50.6189 1.019 50.6992 1.378 69.6103 1.365 41.6110 1.376 41.6917 1.172 50.6215 1.060 50.7026 1.380 69.6131 1.383 41.6141 1.372 41.6951 1.194 50.6239 1.082 50.7062 1.399 69.6155 1.398 41.6164 1.375 41.6982 1.206 50.6267 1.124 50.7085 1.402 69.6185 1.402 41.6196 1.370 41.7015 1.210 50.6288 1.140 50.7112 1.399 69.6211 1.398 41.6222 1.360 41.7049 1.207 50.6349 1.147 50.7139 1.391 69.6234 1.401 41.6266 1.333 41.7069 1.208 50.6374 1.173 50.7167 1.374 69.6273 1.386 41.6284 1.326 41.7106 1.213 50.6401 1.197 50.7193 1.370 69.6300 1.379 41.6322 1.296 41.7137 1.212 50.6424 1.205 69.6348 1.333 41.6350 1.274 41.7183 1.217 50.6447 1.223 68.6098 0.859 69.6371 1.313 41.6389 1.226 41.7231 1.227 50.6475 1.222 68.6124 0.890 69.6403 1.292 41.6412 1.198 41.7316 1.255 50.6505 1.229 68.6159 0.930 69.6426 1.274 41.6437 1.177 41.7347 1.254 50.6530 1.272 68.6183 0.944 69.6453 1.257 41.6463 1.150 41.7380 1.244 50.6563 1.288 68.6210 0.979 69.6491 1.225 41.6494 1.112 41.7412 1.244 50.6584 1.289 68.6244 1.032 69.6515 1.192 41.6519 1.084 41.7458 1.260 50.6652 1.362 68.6285 1.058 69.6545 1.154 41.6551 1.063 41.7491 1.267 50.6683 1.386 68.6316 1.091 69.6348 1.333 41.6569 1.045 50.6721 1.353 68.6370 1.155 41.6605 1.033 50.5956 0.844 50.6750 1.335 68.6390 1.173 A. ARELLANO FERRO Instituto de Astronomia, UNAM, Apdo Postal 70-264, Mexico D.F., 04510. Mexico e-mail: armando@astroscu.unam.mx J.J. AVILA F. GONZALEZ Observatorio de La Luz Universidad de Guanajuato Apdo Postal 144, CP 36000 Guanajuato, Gto., Mexico Reference: Arellano Ferro, A., Nunez, N.S. and Avila, J.J., 1994, PASP, in press (July issue) [BIBCODE 1994PASP..106..696A ]