COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2170 Konkoly Observatory Budapest 1982 June 23 HU ISSN 0374-0676 SUPPLEMENTARY STROMGREN PHOTOMETRY OF THE Ap STARS HD 30849 AND HD 53116 Both Ap stars HD 30849 and HD 53116 have been observed earlier for photometric variability. The results were published by Hensberge et al. (1981). The stars were selected from the Vogt-Faundez paper (1979) because of indication of pronounced variability. The observations of Hensberge et al. confirmed variability up to 0.1m in Stromgren v for HD 30849, and up to 0.1m in Stromgren u for HD 53116. The measurements were used together with the Vogt-Faundez data to derive the period of variability, but no unique solution could be given. In the case of HD 30849, several rotation periods between 15.6 and 16 days could represent the data. In the Case of HD 53116 two possibilities remained open: nearly 12 days or about 18.1 days. Both stars have been reobserved in 1981 in order to remove these ambiguities. The observations were obtained at the ESO 50 cm telescope, by Catalano (HD 30849) and Weiss (HD 53116) respectively, during observing time obtained by the European Ap Workgroup. The comparison stars of Hensberge et al. (1981) were used again, and differential magnitudes were calculated in the same way. The new observations, given in Table I, are compatible only with P = 15.865 +- 0.005 for HD 30849 P = 11.978 +- 0.005 for HD 53116 as the reader can check in the corresponding Figures 1 and 2. Table I JD HD 30849- HD 31640 phi for (phi=0) = HJD 2444197.621+ 2444000+ Deltau_instr Deltav_instr Deltab_instr Deltay_instr Deltaa 15.865E 15.600E 15.731E 15.99E +-0.005 614.736 0.966 0.945 0.824 0.768 - 0.292 0.738 0.516 0.071 +-.009 619.611 0.959 0.895 0.814 0.801 0.021 0.599 0.051 0.825 0.376 +-.009 625.560 1.008 1.005 0.836 0.800 0.032 0.974 0.432 0.204 0.748 +-.009 ----------------------------------------------- ------------------------------------- HD 53116- HD 53238 phi for (phi=0) = HJD 2444230.732+ Deltau_instr Deltav_instr Deltab_instr Deltay_instr 11.978 +- 0.005 18.105 +- 0.007 666.561 0.038 0.334 - - - 0.386 +- 0.015 0.072 +- 0.01 668.538 0.103 0.294 0.382 0.512 0.040 0.551 +- 0.015 0.181 +- 0.01 670.531 0.102 0.301 - - - 0.717 +- 0.015 0.292 +- 0.01 672.535 0.088 0.289 0.381 0.528 0.046 0.885 +- 0.015 0.402 +- 0.01 [FIGURE 1] Fig. 1 Differential observations Delta v and Delta u in the sense HD 30849 - HD 31640, and the variation of the peculiarity index Delta a (Maitzen, 1976) according to the ephemeris (phi=0) = HJD 2444197.621 + 15.8665 E. The new observations are indicated by filled circles. [FIGURE 2] Fig. 2 Differential observations Delta b, Delta v and Delta u in the sense HD 53116 - HD 53238, and the variations of the peculiarity index Delta a (Maitzen, 1976) according to the ephemeris (phi=0) = HJD 2444230.732 + 11.978 E. Symbols have the same meaning as in Figure 1. H. HENSBERGE ^1, W.W. WEISS ^2, F.A. CATALANO ^3, H. SCHNEIDER ^4 1 Astrophysical Institute, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium 2 Institut fur Astronomie der Universitat Wien, Turkenschanzstrasse 17, A-1180 Wien, Austria 3 Osservatorio Astrofisico, Citta del Universitaria, Viale A. Doria, I-95125 Catania, Italia 4 Universitatssternwarte, Geismarlandstrasse 11, D-34 Gottingen, B.R.D. References: Hensberge, H., Maitzen, H.M., Deridder, G., Gerbaldi, M., Delmas, F., Renson, P., Doom, C., Weiss, W.W., Morguleff, N.: 1981, Astron.Astrophys.Suppl. 46, 151. [BIBCODE 1981A&AS...46..151H ] Maitzen, H.M.: 1976, Astron.Astrophys. 51, 223. [BIBCODE 1976A&A....51..223M ] Vogt, N., Faundez, M.: 1979, Astron.Astrophys.Suppl. 36, 477. [BIBCODE 1979A&AS...36..477V ]