COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 644 Konkoly Observatory Budapest 1972 March 21 RADII VARIATIONS IN RZ LYRAE WITH THE BLASHKO-EFFECT Light gradients G_U=dU/dB and G_V=dV/dB for RZ Lyrae have been determined for different phases of the Blashko-effect from observations obtained by Romanov in the system close to that of UBV (IBVS 205, 1967; AZ 612, 1971). The gradients obtained for nearly whole ascending and descending branches of the light curve of primary period proved to be similar though the instantaneous values of G_U in the middle of the ascending branch may have great variations. Thus, each phase of the Blashko-effect (psi) has corresponding definite values of the gradients. Mean gradients for different phases psi which have been selected in such a way as to allow for peculiarities of the light amplitude variations, G_U, G_V and (B-V) are given in Table 1. The position variation of RZ Lyrae with phase psi in the two-gradients diagram is shown in Fig. 1. [FIGURE 1] The mean position of RZ Lyrae calculated from all 527 observations is indicated by a circle at G_U=0.913+-0.008, G_V=0.784+-0.006 and the correlation coefficients r_B^U=0.980+-0.017, r_B^V=0.987+-0.011. Table 1 psi G_U G -V (B-V)_max (B-V)_min delta B_T 0.000 0.961 0.822 0.^m083 0.512 1.774 0.020 0.950 0.815 0.080 0.510 1.786 0.050 0.925 0.810 0.081 0.500 1.754 0.100 0.872 0.790 0.110 0.492 1.594 0.200 0.760 0.765 0.175 0.485 1.227 0.225 0.755 0.757 0.185 0.482 1.177 0.250 0.767 0.750 0.200 0.480 1.106 0.300 0.785 0.748 0.205 0.475 1.080 0.350 0.820 0.745 0.195 0.472 1.117 0.400 0.860 0.740 0.185 0.470 1.141 0.450 0.890 0.740 0.180 0.467 1.165 0.500 0.910 0.750 0.175 0.470 1.190 0.600 0.940 0.775 0.165 0.482 1.258 0.700 0.960 0.810 0.150 0.500 1.394 0.800 0.985 0.845 0.130 0.510 1.535 0.850 1.000 0.868 0.115 0.520 1.640 0.900 1.012 0.850 0.105 0.525 1.713 0.910 1.015 0.848 0.100 0.525 1.740 0.950 0.995 0.837 0.090 0.520 1.766 Table 2 psi (R_1/R2)_U (R_1/R2)_B (R_1/R_2)_V psi (R_1/R_2)_U (R_1/R_2)_B (R_1/R_2)_V 0.000 1.157 1.214 1.164 0.450 1.134 1.136 1.147 .020 1.167 1.216 1.168 .500 1.127 1.139 1.143 .050 1.182 1.212 1.168 .600 1.120 1.148 1.139 .100 1.199 1.191 1.165 .700 1.123 1.165 1.135 .200 1.207 1.144 1.141 .800 1.121 1.183 1.128 .225 1.200 1.138 1.138 .850 1.120 1.197 1.123 .250 1.181 1.129 1.132 .900 1.117 1.206 1.141 .300 1.169 1.126 1.131 .910 1.117 1.210 1.145 .350 1.159 1.130 1.135 .950 1.133 1.213 1.156 .400 1.144 1.133 1.141 From considering the cepheid sequence in the gradient diagram by Kolesnik it was found (Astron. Astrph. Nos 12,13, 1971. Kiev) that light gradients may be represented by the linear relationship (1-P_2 G_U) G_V=G_V^T/G_U^T ----------- P_1 where for condition of a general zero-point of all the straight lines P_1=0.934 G_T^V/G_U^T or for condition of parallel straight lines P_2/P_1=0.316 G_U^T/G_V^T Here G_U^T and G_V^T are light gradients defined by the temperature variations in the star. G_U^T=0.912 and G_V^T=0.815 have been obtained for de C. Jager's atmosphere models with lg g=3. The conditions of general zero-point and parallel straight lines give similar results. Therefore let us consider only the conditions of a general zero-point. In this case the relationships for calculating the relative variations of effective UBV-radiation levels of the star may be represented by expressions a_U=G_U^T n_U B_T, a_B=n_B B_T, a_V=G_V^T n_V B_T, (2) where a_Q=5lg(R_1/R_2)_Q, Delta B_T=6.75 Delta Theta, Theta =5040/T_e and n_U=1-p_A G_U, n_B=1-p_A G_U^T, n_V=p_2 G_U (3) on the basis of known determinations of spectral types near to the light maximum (Alanija, Abastumani Bull. No. 23, 1958) and to our mean values of (B-V)_max we must assume rather precisely for further calculations that (B-V) are not effected by interstellar absorption. Then, using the Johnson calibration (Ann. Rev. Astr. Astrph. 4, 193, 1966) maximum (2) and minimum (1) of the light of primary period, we could determine T_e and calculate delta B_T given in Table 1. To determine T_e in the light minimum we have taken (B-V) with the phase of the primary period psi=0.5. The estimated results of radii relationships are given in Table 2 and Fig. 2. [FIGURE 2] One can see that the relative radius amplitude for each range UBV is maximum near the maximum of the Blashko-effect with different phase shift. The minimum amplitude of radius variations is obtained in the V range. A more detailed scope of information on the investigation will be published in "Astrometry and Astrophysics", No 18, Kiev, "Naukova Dumka", 1972. I.G. KOLESNIK The Main Astronomical Observatory of the Ukranian Academy of Sciences YU.S. ROMANOV The Odessa Astronomical Observatory