COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1553 Konkoly Observatory Budapest 1979 February 16 B V OBSERVATIONS OF SIX RED VARIABLE STARS Using an uncooled RCA 1P21 photomultiplier behind Schott filters BG 12 + GG 13 for B and GG 11 for V, photoelectric observations of red variable stars were made with the 75 cm telescope of the Wilhelm-Foerster Observatory. Four of the measured stars belong to the Mira-Ceti type, and the others are of type SRa (W Cyg) and Lb (VY UMa). Table 1 lists the obtained observations and Table 2 contains the used comparison stars. Some magnitudes and colours of comparison stars are taken from the USNO-catalogue, the rest was determined by measuring nearby standard stars. It is well known from visual observations that Mira variable stars differ in maximum heights and light-curve from cycle to cycle. A comparison of the presented measurements of Chi Cyg and T Cep with older UBV observations of Landolt (1968, 1969) at the same phase of the V-light-curve shows that also the colour (B-V) differs, too, from cycle to cycle. The presented colour (B-V) of the SRa star W Cyg is constant during the observed rise in V. This is in good agreement with the measurements of Smak (1964) during a decline. The accuracy of the presented observations is in the order of +-0.02m for V and in the order of +-0.01m for (B-V). U. HOPP Wilhelm - Foerster Observatory Berlin References: Landolt, A.U., 1968, Publ.Astron.Soc.Pacific 80, 680 [BIBCODE 1968PASP...80..680L ] 1969, Publ.Astron.Soc.Pacific 81, 134 [BIBCODE 1969PASP...81..134L ] Smak, J., 1964, Astrophys. J. Suppl. S. 9, 141 [BIBCODE 1964ApJS....9..141S ] Table 1 Observations --------------------------------------------------- Star Julian Date V B-V --------------------------------------------------- T Cep 2443 790d 6.01 +1.52m 794 6.11 1.47 808 6.42 1.54 828 7.00 1.58 833 7.16 1.59 847 7.53 1.60 862 8.05 1.64 R Cyg 328 8.15 1.81 W Cyg 794 6.29 1.51 808 6.27 1.57 828 6.00 1.46 833 5.84 1.51 848 5.57 1.58 Chi Cyg 790 4.43 1.66 794 4.49 1.86: 828 5.75 1.73 832 5.87 1.87 848 6.46 1.90 R Tri 808 9.24 1.35 833 8.45 1.19 848 7.82 1.12 862 6.95 1.18 VY UMa 254 6.10 2.43: 605 6.15 2.52 606 6.14 2.43: --------------------------------------------------- The observation of R Cyg was made with the 12" refractor and the first observation of VY UMa was made with the 6" refractor of the Wilhelm Foerster Observatory. Table 2 Comparison Stars ----------------------------------------------------- Star V B-V Variable ----------------------------------------------------- SAO 019214 6.95m +0.06m T Cep 019211 8.17 +0.27 031845 9.00 +1.50 R Cyg 031823 9.91 -0.09 051109 6.19 +0.19 W Cyg 051161 6.72 -0.06 068827 4.97 +0.47 Chi Cyg 068895 6.46 +0.20 068835 6.18 +1.13 068902 7.51 +1.24 055741 7.85 +0.54 R Tri 055744 8.29 +1.22 015269 5.00 +1.39 VY UMa -----------------------------------------------------