COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3478 Konkoly Observatory Budapest 12 June 1990 HU ISSN 0374 - 0676 FIRST BV LIGHT CURVE FOR THE ECLIPSING BINARY PP LACERTAE PP Lac was discovered by Miller on photographic plates taken in 1948 - 1955 at Castel Gandolfo. Miller and Wachmann (1971) found an amplitude of 0.9 mag. (11.1 - 12.0 p) and a period of about 0.5d. The type of variation proposed was EW or RR. Figer and Rolland (1976 and 1977), from visual estimates made by GEOS members, classified it as an EW-type variable, with a period of 0.4011d. They could not discriminate the primary minimum from the secondary one, so a doubt still remained on the type of variation of the star. The GCVS (Kholopov et al., 1985) classifies the star as EW/KW, and gives the following elements: 11.1 - 12.0 p; min II 12.0; Min I = JD Hel 2445595.438 + 0.401163d * E Recently, Maraziti (1989) reexamined all visual observations made by GEOS members from 1976 to 1988. Collecting 128 minima from 17 observers, plus 18 other minima published by Locher (1977, 1978, 1979), he found the following ephemeris: Min I (or II) = JD Hel 2442903.235 + 0.40116150d * E (1) +/-2 +/-48 (95% level of confidence for error bars). He was not able to distinguish between primary and secondary minimum. In order to check this result by means of photoelectric measures, PP Lac was selected as one of the targets of GEOS missions at Jungfraujoch Observatory. Four missions were performed in 1985, 1986, 1988 and 1989, though most of observations were made during the last one. The GEOS members who took part in the different missions were M. Dumont, J. Remis, J.C. Misson, S. Ferrand, P. Louis, Ph. Rousselot, E. Joffrin, R. Boninsegna, R. Lecocguen. The observations were made using a photometer attached to the 76 cm telescope. B and V filters of the Geneva system were used, and the B-V values were turned into Johnson and Morgan system. 132 measures in each colour were obtained in 4 nights, Table I PP Lac - photoelectric observations JD (hel) V B-V phase JD (hel) V B-V phase 2440000+ (1) 2440000+ (1) 6266.4390 11.576 0.769 0.666 7775.4154 11.391 0.745 0.184 6266.4626 11.496 0.775 0.725 7775.4390 11.523 0.734 0.243 6266.4939 11.53ó 0.758 0.803 7775.4411 11.529 0.728 0.248 6266.5195 11.660 0.781 0.867 7775.4425 11.522 0·743 0.252 6266.5550 12.045 0.780 0.955 7775.4453 11.541 0.733 0.259 6266.5793 12.186 0.839 0.016 7775.4467 11.550 0.724 0.262 7378.5694 12.017 0.754 0.942 7775.4480 11.547 0.730 0.266 7378.5721 12.077 0.762 0.949 7775.4494 11.547 0.728 0.269 7378.5735 12.061 0.795 0.952 7775.4529 11.542 0.743 0.278 7378.5742 12.108 0.775 0.954 7775.4543 11.534 0.752 0.281 7378.5756 12.097 0.795 0.957 7775.4557 11.556 0.726 0.285 7378.5763 12.146 0.773 0.959 7775.4571 11.570 0.707 0.288 7378.5791 12.168 0.789 0.966 7775.4585 11.554 0.736 0.292 7378.5812 12.161 0.851 0.971 7775.4779 11.616 0.747 0.340 7378.5937 12.193 0.848 0·003 7775.4793 11.621 0.750 0.344 7378.5951 12.199 0.812 0.006 7775.4807 11.622 0.757 0.347 7383.4603 11.617 0.741 0.134 7775.4821 11.632 0.744 0.351 7383.4652 11.628 0.743 0.146 7775.4855 11.655 0.767 0.359 7383.4673 11.622 0.752 0.151 7775.4869 11.653 0.758 0.363 7383.4694 11.612 0.748 0.156 7775.4883 11.658 0.769 0.366 7383.4714 11.594 0.750 0.161 7775.4897 11.666 0.764 0.370 7383.4888 11.508 0.735 0.205 7775.4911 11.677 0.760 0.373 7383.4909 11.504 0.733 0.210 7775.4925 11.695 0.748 0.377 7383.4930 11.508 0.732 0.215 7775.4953 11.712 0.745 0.384 7383.4971 11.500 0.728 0.226 7775.4967 11.709 0.759 0.387 7383.4999 11.504 0.719 0.232 7775.4980 11.728 0.752 0.390 7383.5020 11.508 0.727 0.238 7775.4994 11.749 0.744 0.394 7383.5069 11.518 0.725 0.250 7775.5008 11.746 0.766 0.397 7383.5096 11.514 0.740 0.257 7775.5043 11.776 0.769 0.406 7383.5124 11.521 0.736 0.264 7775.5057 11.772 0.774 0.410 7383.5152 11.520 0.739 0.271 7775.5071 11.789 0.779 0.413 7383.5201 11.520 0.734 0.283 7775.5085 11.808 0.769 0.416 7383.5221 11.535 0.736 0.288 7775.5098 11.819 0.773 0.420 7775.3779 11.773 0.758 0.091 7775.5112 11.849 0.765 0.423 7775.3828 11.735 0.752 0.103 7775.5126 11.907 0.750 0.427 7775.3855 11.724 0.751 0.110 7778.5175 11.936 0.755 0.439 7775.3897 11.696 0.744 0.120 7775.5189 11.949 0.765 0.442 7775.3911 11.698 0.743 0.124 7775.5203 11.966 0.755 0.446 7775.3925 11.682 0.743 0.127 7775.5217 11.984 0.763 0.449 7775.3939 11.680 0.735 0.131 7775.5230 12.005 0.760 0.453 7775.3980 11.626 0.759 0.141 7775.5244 12.016 0.775 0.456 7775.3994 11.629 0.751 0.145 7775.5272 12.123 0.740 0.4ó3 7775.4008 11.626 0.752 0.148 7775.5286 12.107 0.781 0.467 7775.4022 11.623 0.741 0.152 7775.5300 12.116 0.779 0.470 7775.4036 11.614 0.756 0.155 7775.5314 12.112 0.792 0.474 7775.4050 11.623 0.745 0.158 7775.5328 12.111 0.791 0.477 7775.4092 11.603 0.746 0.169 7775.5369 12.169 0.788 0.487 7775.4105 11.597 0.741 0.172 7775.5390 12.167 0.787 0.493 7775.4119 11.597 0.745 0.176 7775.5439 12.125 0.784 0.505 7775.4133 11.596 0.749 0.179 7775.5460 12.104 0.799 0.510 Table I (cont.) JD (hel) V B-V phase JD (hel) V B-V phase 2440000+ (1) 2440000+ (1) 7775.5480 12m081 1m789 0.515 7775.5897 11m675 0.748 0.619 7775.5494 12.071 0.787 0.518 7775.5918 11.648 0.760 0.624 7775.5598 11.920 0.805 0.544 7775.5932 11.643 0.756 0.628 7775.5619 11.897 0.799 0.550 7775.5973 11.625 0.761 0.638 7775.5633 11.884 0.792 0.553 7775.5987 11.626 0.745 0.641 7775.5647 11.872 0.785 0.557 7775.6001 11.609 0.755 0.645 7775.5696 11.828 0.778 0.569 7775.6154 11.538 0.766 0.683 7775.5710 11.796 0.776 0.572 7775.6168 11.531 0.759 0.686 7775.5723 11.788 0.786 0.576 7775.6189 11.548 0.744 0.692 7775.5744 11.769 0.762 0.581 7775.6210 11.530 0.752 0.697 7775.5779 11.747 0.769 0.589 7775.6251 11.521 0.753 0.707 7775.5793 11.721 0.774 0.593 7775.6272 11.526 0.744 0·712 7775.5814 11.716 0.765 0.598 7775.6286 11.527 0.741 0·716 7775.5828 11.688 0.776 0.602 7775.6307 11.524 0.748 0.721 7775.5842 11.673 0.770 0.605 7775.6328 11.527 0.747 0.726 7775.5876 11.686 0.745 0.614 7775.6342 11.528 0.743 0.730 [FIGURE 1a] All observations are listed in Table I. Figure I shows the V and B-V light curves obtained according to ephemeris (1). One can note a good agreement with this ephemeris. The shape of light curves is typical of an EW-type variable, with nearly equal minima and quasi-constant B-V index. One can note a slight increase of B-V index during both minima. This might be due to the disappearance, during minima, of the contact zone between the two stars, which has a higher temperature than the rest of their surfaces. [FIGURE 1b] It is apparent a slight difference in the V magnitude between the two minima: min I is 12.20 while min II is 12.17. This difference, however, is too small to be considered significant. More precise observations are needed to establish the magnitudes of minima. The mean B-V, not corrected for reddening, is 0.76. On the night of September 5, 1989, it was possible to observe a complete secondary minimum, at JD Hel 2447775.5380 +/- 0.0010; the time of minimum was calculated using the technique described by Gaspani (1988). The O-C calculated from (1) is -0.0042d, which is a further confirmation of the above GEOS ephemeris (1). M. DUMONT 1,2 A. MARAZITI 1 GEOS 2 Palais de la Decouverte 3, promenade Venezia Avenue Franklin D. Roosevelt F-78000 Versailles F-75008 Paris References: Figer, A., Rolland, R.: 1976, GEOS NC 142. Figer, A., Rolland, R.: 1977, I.B.V.S. No. 1231. Gaspani, A.: 1988, Fiche techn. GEOS FT 30: Ricerca di estremi di curve di luce di stelle variabili mediante tecniche di ottimizzazione via approssimazione stocastica. Kholopov, P.N. et al.: 1985, General Catalogue of Variable Stars. Locher, K.: 1977, BBSAG Bulletin, Nos 32, 33, 35. Locher, K.: 1978, BBSAG Bulletin, Nos 38, 40. Locher, K.: 1979, BBSAG Bulletin, Nos 42, 44, 45. Maraziti, A.: 1989, GEOS Circular on Eclipsing Binaries (to be printed), Miller, W.J., Wachmann, A.A.: 1971, Ricerche Astronomiche, 8, No. 12. [BIBCODE 1971RA......8...12M ]