COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3661 Konkoly Observatory Budapest 20 September 1991 HU ISSN 0374 - 0676 1989, 1990 PHOTOELECTRIC LIGHT CURVES OF RT And The star RT And has been classified by Hall (1976) as an object of the "Short-Period Group" with properties similar to the RS CVn. Photometric observations for this star have been reported previously by several investigators listed by Dapergolas et al. (1988). The star was observed photoelectrically for a total of 10 nights with the 1.2m Kryonerion telescope from October 3, 1989 to August 29, 1990 using a single channel photon counting photometer described by Dapergolas and Korakitis (1987). The photometer employs a high gain 9789QB phototube and UBV conventional filters. Its output is fed directly to a microcomputer enabling rapid data access. The data reduction method is the standard one. Comparison and check stars are the BD+52d 3384 and BD+52d 3377 respectively and the accuracy of the observations presented here is +-0.015mag for V,B and +-0.025 for U. Table I lists the dates of observations and phases covered. The derived light curves for U, B, V colours are illustrated in Figures 1, 2, 3. Dots are for the year 1990 and crosses for 1989. Table I DATE PHASE 3 Oct. 1989 .88- .07 6 Oct. 1989 .43- .82 7 Oct. 1989 .12- .44 21 Aug. 1990 .94- .12 22 Aug. 1990 .30- .71 25 Aug. 1990 .02- .48 26 Aug. 1990 .65- .07 27 Aug. 1990 .61- .67 28 Aug. 1990 .79- .19 29 Aug. 1990 .43- .85 In Table II the times of minima and the O-C values are listed for the V, B and U bands respectively. Times of minima are calculated using the method described by Kwee and van Woerden (1956) whereas the O-C values were determined from the linear ephemeris T = 2441141.88902 + 0.628929513d.E given by Kholopov, (1982). Our light curves show asymmetry in the secondary minima that gets larger in short wavelengths, and different for the two observed periods 1989 and 1990. [FIGURE 1] [FIGURE 2] [FIGURE 3] Table II V COLOUR B COLOUR U COLOUR Type Heliocen. (O-C) Heliocen. (O-C) Heliocen. (O-C) Jul. Day phase Jul. Day phase Jul. Day phase, 2440000+ 2440000.+ 2440000.+ I 7803.5094 0.998 7803.5094 0.998 ---- ---- +-0.0001 +-0.0002 II 7806.3389 0.497 7806.3404 0.500 ---- ---- +-0.0005 +-0.0003 I 8125.5203 0.997 8125.5204 0.997 8125.5201 0.997 +-0.0001 +-0.0001 +-0.0001 II 8126.4662 0.501 8126.4665 0.501 8126.4643 0.498 +-0.0001 +-0.0002 +-0.0008 I 8130.5517 0.997 8130.5519 0.997 8130.5519 0.997 +-0.0001 +-0.0001 +-0.0001 I 8132.4386 0.997 8132.4386 0.997 8132.4386 0.997 +-0.0001 +-0.0001 +-0.0001 II 8133.3832 0.499 8133.3856 0.503 8133.3858 0.503 +-0.0003 +-0.0003 +-0.0004 The variability in the levels of maxima noticed previously by Mancuso et al.(1979) and Dapergolas et al.(1988) it is present here as it can be seen in Figures 2 and 3. This is due to a photospheric activity of the system, Gordon et al.(1990), probably attributed to the presence of a spotted region. A. DAPERGOLAS and E. KONTIZAS M. KONTIZAS National Observatory of Athens University of Athens Astronomical Institute Laboratory of Astrophysics P.O. Box 20048 Panepistimiopolis GR Athens 118-10 GR Athens 151-71 Greece Greece References: Dapergolas, A., Korakitis, R.: 1987, Publ. Nat. Obs. of Athens, Ser. II, N28. Dapergolas, A., Kontizas, E., Kontizas, M.: 1988, I.B.V.S., No. 3267. Gordon, S., Hall, M., Ledlow, M., Mann, E. and Zeilik, M.: 1990, I.B.V.S., No. 3469. Hall, D.S.: 1976, in: "Multiple Periodic Variable Stars", Proc. IAU Coll. No. 29, ed. W.S. Fitch, Akademiai Kiado, Vol. 1. [BIBCODE 1976ASSL...60..287H ] Kholopov, P.N.: 1982, "General Catalogue of Variable Stars", IVth edition, vol. I, p103. Kwee, K.K., van Woerden, H.: 1956, Bull. Astr. Inst. Netherlands, 12, 327. [BIBCODE 1956BAN....12..327K ] Mancuso, S., Milano, L. and Russo, G.: 1979, Astron. Astrophys. Suppl. Ser., 36, 415. [BIBCODE 1979A&AS...36..415M ]