COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1049 Konkoly Observatory Budapest 1975 October 6 Veroffentlichungen der Dr. Remeis-Sternwarte Bamberg Astronomisches Institut der Universitat Erlangen-Nurnberg Vol. X, No. 113 LIGHT CHANGES OF T TAURI STARS IN THE CHAMAELEON ASSOCIATION During a stay at the Boyden Observatory a star field around epsilon Cha, which included Hoffmeister's T Association, was photographed as often as possible. The instrument used was the 10" Metcalf refractor of the Boyden Observatory, the exposures were taken on Gevaert 67A50 plates. A total of 102 plates on 31 nights could be obtained. All stars classified as T Tau stars which were not too faint were included, the photographic magnitude of all stars was obtained by the Argelander method. On three of the best plates the numerous comparison stars needed were measured, together with standard sequence stars of the selected area SA 203; with the Iris Photometer of the Remeis Observatory, Bamberg. The period of 3.2d is clearly found for T Cha. For SY Cha the times of maximum and minimum light are well represented with a peribd of 6.2d; somewhat less pronounced is a period of 7d in VZ Cha. In the latter case a phase shift may have happened around J.D. 244 1398. There also some indication of a period of 8d in TW Cha, but in this case the observations are too poor. In the meantime the stars SY Cha, VZ Cha and TW Cha were observed photoelectrically in UBV at the ESO Observatory, La Silla. The preliminary reduction of the data shows clearly light and colour changes which are in full agreement with the photographically derived quasiperiodic changes. A grant of the "Deutsche Forschungsgemeinschaft", which enabled one of us (H.M.) to do the observations at Boyden, is gratefully acknowledged. H. MAUDER F.M. SOSNA Astronomisches Institut Dr. Remeis-Sternwarte Bamberg der Universitat Tubingen ------------------------------------------------------------------------------------------------------------------------------------------- J.D. 244.. T Cha ST Cha SW Cha SX Cha SY Cha SZ Cha TW Cha UV Cha VW Cha VZ Cha WW Cha WY Cha BC Cha ------------------------------------------------------------------------------------------------------------------------------------------- 1299.48 - 14.37m 14.06m 15.74m 13.30m 13.49m 14.52m 14.69m 13.68m 12.57m 15.19 14.96m - 1300.48 13.04m 13.94 14.06 - 12.51 14.48 14.22 15.31 13.79 12.57 15.59 14.96 - .51 12.95 13.99 14.43 15.98 12.44 14.60 14.22 14.91 13.76 12.36 15.09 15.01 - .53 12.86 14.10 14.35 15.74 12.64 14.09 14.12 15.16 13.72 12.77 15.09 14.36 - 1306.48 13.35 13.89 14.35 15.23 13.00 13.42 13.83 14.82 13.58 14.17 15.51 14.85 - .51 13.35 13.89 14.50 15.38 12.94 13.35 13.83 14.82 13.65 13.80 - 14.85 - .53 13.47 14.12 14.06 15.40 12.89 13.35 14.12 14.91 13.50 13.84 15.51 14.84 - .55 13.04 14.20 14.35 14.91 12.89 13.49 13.83 15.31 13.65 13.73 - 14.84 - 1307.42 11.50 14.17 14.35 14.35 12.64 14.01 14.02 14.91 13.76 13.80 15.51 14.96 - .44 11.52 14.37 14.35 14.25 12.64 14.01 14.02 15.31 13.76 13.73 15.09 14.84 - .46 11.50 14.67 14.50 14.25 12.89 14.09 13.83 14.91 13.96 13.80 15.04 14.96 - .48 11.50 14.67 14.35 14.67 12.89 14.17 14.02 14.91 13.79 13.54 15.19 14.84 - 1308.44 11.50 13.99 14.18 15.74 13.00 13.49 14.12 14.91 13.72 13.29 14.99 14.71 - .46 11.50 13.99 14.35 15.63 12.89 13.49 14.02 13.31 13.65 13.55 15.04 14.78 - .48 11.52 13.89 14.35 15.50 13.00 13.49 14.12 14.91 13.72 13.54 15.27 14.99 1339.38 - 14.20 14.35 15.26 13.00 13.62 14.73 15.31 14.25 14.11 14.73 14.96 15.68m .40 15.19 14.59 14.50 15.19 13.00 13.65 14.93 15.47 14.25 14.23 14.56 15.06 15.89 .42 15.19 14.68 14.06 15.63 13.00 13.06 14.73 15.46 14.06 13.80 14.88 14.86 15.68 .44 15.19 14.68 14.66 14.67 13.00 13.49 14.52 15.16 14.25 13.80 14.88 14.82 - .48 15.19 14.10 14.50 15.51 13.68 13.49 14.73 14.91 14.35 13.84 14.52 14.64 15.89 1340.38 12.86 13.89 14.50 15.74 14.39 12.93 14.22 14.91 13.96 14.97 15.04 15.04 15.49 .40 12.86 13.94 14.50 15.51 14.94 13.35 14.12 14.91 14.35 14.81 14.59 15.01 15.89 .42 13.04 13.77 14.06 15.74 14.73 13.20 14.12 14.91 13.96 14.81 14.73 15.13 15.49 .44 12.34 13.99 14.50 - 14.39 12.93 14.22 14.82 14.06 14.81 14.88 15.14 15.49 .46 12.77 13.99 14.35 - 14.39 12.93 14.02 14.68 13.79 14.89 14.61 15.12 15.68 .48 12.69 14.17 14.50 15.63 '4.39 13.29 14.52 14.91 13.79 14.81 14.88 15.27 15.52 .50 12.66 14.19 14.81 15.74 14.39 13.06 14.12 14.91 13.79 14.89 14.75 15.13 15.56 .52 13.04 14.10 14.43 15.98 14.49 13.22 14.07 15.16 13.76 14.81 14.70 15.29 15.49 1351.31 13.04 13.89 14.50 16.46 13.30 13.42 14.93 15.16 13.72 13.80 15.04 15.12 - 1352.37 13.98 14.10 14.81 - 14.39 13.35 14.31 14.70 13.68 13.73 14.70 15.27 - 1353.35 13.35 14.12 14.57 15.21 14.19 12.93 14.93 14.91 14.35 14.11 15.27 15.24 15.82 .37 13.65 14.52 14.06 15.19 14.29 12.93 14.93 14.70 14.35 13.87 15.09 - 15.49 1354.36 15.26 13.99 14.35 15.03 13.86 13.00 14.52 15.31 13.83 14.29 15.04 15.27 15.05 .38 15.26 13.99 14.35 14.91 13.91 13.06 14.22 14.91 14.06 14.29 14.99 15.06 15.03 .40 15.11 13.77 i4.50 14.67 14.19 12.59 14.12 15.31 14.01 14.29 15.09 15.19 15.08 1355.36 13.85 14.45 14.50 15.63 13.95 13.35 14.02 14.69 13.79 13.54 14.99 15.27 15.79 .38 13.92 14.19 14.81 15.74 13.91 13.35 13.83 14.91 13.79 13.54 15.04 15.29 15.61 1355.40 13.85m 14.20m 14.43m 15.74m 13.68m 13.35m 14.02m 14.91m 13.79m 13.56m 15.04m 15.19m 15.89m 1356.38 12.71 14.10 14.35 15.86 13.00 13.06 14.12 15.31 13.76 12.99 - 15.27 15.96 .41 12.86 13.89 14.06 15.98 12.94 13.06 14.22 15.31 13.76 12.78 15.89 15.32 15.68 .43 12.42 13.94 14.43 15.74 13.00 13.06 14.22 14.91 13.76 12.95 15.43 15.14 15.49 .45 12.86 14.11 14.35 16.46 13.00 12.93 - 15.42 13.72 12.95 15.51 15.12 15.19 1357.37 13.85 14.52 14.35 15.98 13.58 13.49 14.22 14.82 13.65 12.36 - 15.13 15.49 .39 13.93 14.68 14.35 16.23 13.91 13.49 14.22 14.70 13.61 12.77 15.89 15.13 15.24 .42 13.98 14.67 14.35 15.74 13.58 13.49 14.12 14.91 13.58 12.90 15.51 15.12 15.29 .44 13.98 14.19 14.43 16.23 - - - - 13.61 - - - 15.23 1358.37 13.41 13.99 14.43 16.23 14.62 13.42 14.31 14.91 13.58 13.07 15.51 14.92 - .39 13.41 13.77 14.50 15.98 14.62 13.67 14.22 14.91 13.65 12.99 15.59 14.68 15.75 .41 13.04 13.94 14.35 15.74 14.83 13.49 14.22 - 13.79 - - - 15.42 .43 12.86 13.99 14.58 15.98 14.83 13.49 14.12 15.01 13.79 12.82 15.04 14.84 15.49 1359.34 11.77 14.20 14.50 - 15.04 13.13 13.36 14.91 13.76 12.80 - 14.71 15.08 .36 11.98 14.20 14.50 16.46 14.59 13.22 13.50 15.16 14.25 12.80 15.51 14.81 15.29 .49 11.50 14.10 14.35 15.74 15.04 13.49 13.50 15.31 13.96 13.03 15.04 14.86 14.81 1360.43 13.65 14.10 14.50 16.23 14.29 13.35 13.50 14.82 13.96 13.14 14.88 14.86 14.69 .45 13.93 14.12 14.50 15.63 14.19 13.35 13.83 14.68 13.68 13.22 14.99 14.85 14.69 1361.34 14.23 14.20 14.35 15.74 13.49 13.55 14.22 14.91 14.25 13.80 14.73 14.92 14.69 1382.26 13.04 14.11 14.50 - 13.58 13.49 14.52 14.82 14.15 14.11 15.09 15.12 15.28 .28 13.47 14.19 14.35 15.74 13.49 13.55 14.52 14.68 14.25 14.17 14.56 15.11 15.23 .30 13.21 14.12 14.50 15.63 13.49 13.35 14.52 14.82 13.76 14.29 15.09 15.01 15.28 1383.25 - 14.10 14.50 15.63 14.39 13.35 14.31 14.91 14.25 13.73 15.51 15.24 15.10 .27 14.12 14.27 14.39 13.49 14.22 14.91 14.30 14.17 15.14 14.96 14.86 1391.35 - - - - 13.58 13.55 14.12 - 13.71 - - - - 1393.42 14.34 14.12 14.50 - 12.22 13.49 14.07 14.2 - - - 14.01 1394.26 - - - - 12.30 - - - - - - 1396.28 12.58 14.52 14.50 - 13.68 13.49 14.07 14.06 14.29 14.72 1.397.24 13.47 14.17 14.35 -- 13.58 13.29 13.50 14.69 14.35 12.86 15.04 15.29 .26 13.47 13.99 14.50 15.50 13.49 13.13 13.73 15.24 14.35 12.90 14.74 15.11 15.68 .28 13.30 13.99 14.43 - 13.68 12.93 14.07 14.72 14.35 12.81 15.09 15.13 - .30 13.35 14.52 14.50 15.63 13.91 13.06 13.50 14.91 14.35 12.90 15.51 14.86 15.52 .35 13.47 14.67 14.66 - 14.19 13.06 13.73 15.16 14.35 12.90 15.09 15.01 15.68 .37 13.35 14.37 14.50 - 14.29 13.06 14.07 14.91 14.35 12.90 14.75 14.86 - .49 13.35 - - - - 13.06 14.07 - - 12.86 - - - .51 13.04 - - - - 12.93 - - - 12.90 - - - 1398.32 11.53 13.89 14.06 - 12.78 13.35 14.22 14.69 14.35 12.90 14.94 14.81 - 1398.35 11.29m 13.99m 14.35m 15.63m 12.89m 13.49m 14.12m 15.16m 14.35m 12.99m 14.56m 14.96m 15.75m .37 11.52 13.89 14.50 - 12.64 13.42 14.22 14.91 13.83 12.99 14.59 15.12 - .39 11.52 13.94 14.12 - 12.89 13.49 14.22 15.24 14.25 12.99 14.88 15.19 - 1399.36 11.98 14.52 14.50 - 12.89 13.67 14.93 14.72 13.96 14.28 14.73 15.01 15.61 .38 12.34 14.37 14.35 15.50 12.89 13.55 14.83 14.87 14.25 13.80 14.74 15.14 15.44 .40 11.98 13.99 14.50 - 12.64 13.42 14.93 14.69 13.79 14.29 14.53 15.01 15.37 1412.29 15.11 13.99 14.66 15.50 13.58 13.42 13.50 14.27 13.79 14.29 14.80 14.99 14.35 .31 15.11 13.94 14.35 15.03 13.68 13.49 13.50 14.69 14.06 14.35 14.88 14.84 14.35 1416.23 12.18 14.10 14.50 15.26 13.68 13.35 14.93 14.69 13.50 13.56 14.99 14.94 14.24 .25 12.34 14.17 14.43 15.50 13.91 13.42 14.93 14.70 13.50 13.80 15.04 14.84 14.12 .27 12.50 14.17 14.50 15.50 13.91 13.29 15.14 14.67 15.50 14.05 14.53 15.14 14.12 .29 11.98 13.77 14.35 - 13.68 13.35 14.73 14.91 13.58 13.84 14.74 14.86 14.06 .31 11.98 13.89 14.35 15.50 13.40 13.35 14.93 14.91 13.65 13.80 14.59 14.71 14.24 .33 11.98 13.77 14.50 15.74 13.68 13.49 15.35 14.72 13.72 13.77 14.53 14.85 14.06 1419.36 14.17 14.11 14.12 - 13.30 13.49 14.02 14.69 14.35 13.77 - 14.99 14.41 1423.24 14.46 13.99 14.50 - 12.78 i3.92 14.93 14.69 14.45 12.90 14.75 14.85 15.42 .26 13.85 13.99 14.50 15.63 12.64 13.66 15.14 14.67 14.45 12.78 14.69 15.01 14.81 .28 13.74 14.37 14.50 15.50 12.64 13.49 14.93 14.91 14.45 12.77 14.99 14.86 14.81 .30 14.23 14.20 14.43 15.50 12.64 13.49 14.73 14.69 14.35 12.36 14.59 14.96 15.05 .32 14.23 14.67 14.50 - 12.78 13.62 14.93 14.91 14.45 12.58 14.61 14.94 14.81 .34 13.98 14.66 14.43 15.19 12.64 13.49 14.93 14.67 14.65 12.77 14.74 14.85 15.05