COMMISSION 27 OF THE I. A. U
      INFORMATION BULLETIN ON VARIABLE STARS
                   NUMBER 259

                               Konkoly Observatory
                               Budapest
                               1968 March 7


       RT LACERTAE - A PHOTOMETRIC PUZZLE


In 1965 at Kitt Peak National Observatory, UBV photoelectric observations were
made of the eclipsing binary RT Lacertae. The 36-in. telescope was used in
August and the No.4 16-in. in October. The data are given below. Column 1 is
the date. Column 2 is the phase calculated using the elements
2421913.499+5.^d074052 E. Column 3 is the differential V magnitude in the
sense RT Lac minus BD+42d4270. Columns 4 and 5 are the B-V and U-B indices;
these were measured directly with respect to several UBV standards, not
differentially with respect to the comparison star.

Date     P    Delta V    B-V    U-B
Aug
19-20  .9817   2.174
       .9821   2.134
       .9935   1.954
       .9939   1.944
       .9945   1.944
       .9994   1.924
       .9998   1.864
       .0004   1.884
       .0014   1.864
Oct
1-2    .4532   1.865
       .4538   1.879
       .4557   1.879
       .4620   1.919
       .4661   1.958
       .4667   1.953
1-2    .4688   1.969
       .4712   1.964   1.152   1.028
       .4720   1.975
       .4724   1.989
       .4734   1.975
       .4736   1.971   1.157   1.043
       .4744   1.965
       .4768   1.947   1.161   1.005
       .4797   1.919
       .4811   1.912
       .4815   1.900
       .4834   1.895
       .4872   1.855
       .4892   1.867
Oct
24-25  .9704   2.247   1.038   0.735
       .9714   2.272   1.003    .751
       .9720   2.257   1.027    .738
       .9736   2.257
       .9738   2.267   1.005    .806
       .9746   2.252   1.029    .759
       .9752   2.247
       .9756   2.252
       .9760   2.267   1.006    .772
       .9766   2.237
       .9780   2.237
       .9785   2.217
       .9811   2.212
       .9921   1.997
       .9923   1.982
       .9927   1.982
       .9957   1.922
       .9963   1.912
       .9967   1.917
       .9978   1.892
       .9980   1.887
       .0027   1.822
       .0030   1.822

28-29  .7806   1.208   1.076    .837
Oct
29-30  .9622   2.167
       .9626   2.172
       .9630   2.182
       .9636   2.187
       .9653   2.207
       .9665   2.222   1.066    .692
       .9675   2.232   1.044    .702
       .9685   2.252
       .9700   2.282   1.031    .711
       .9706   2.252
       .9782   2.207
       .9787   2.202
Oct
31-1   .3544     -     1.225    .828
       .3579     -     1.107    .920

An intriguing, paradox is apparent from the data. Both the B-V and U-B indices
suggest that the cooler star is visible at secondary minimum and the hotter
star is visible at primary minimum.


DOUGLAS S. HALL
Kitt Peak National Observatory and Indiana University
(present address: Dyer Observatory Nashville, Tennessee)