COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 781 Konkoly Observatory Budapest 1973 April 13 LARGE POLARIZATION VARIATIONS IN CIT 6 An infrared object CIT 6 = IRC +30219 is known to have large, variable, intrinsic polarization (Kruszewski 1971, Dyck et. al. 1971). It was classified as a cool carbon star (Wisniewski et al. 1967, Pesch 1967, Lockwood 1970). New set of observations was obtained with the Steward Observatory 230 cm and Lunar and Planetary Laboratory 154cm reflectors. The following table lists new polarimetric measurements together with estimates of brightness. ------------------------------------------------ J.D. Filter m P% m.e. theta deg 2441000+ ------------------------------------------------ 635.948 I 9.6 7.6 +-1.1 116 651.057 I 8.1 0.6 114 655.828 I 8.1 0.5 115 635.957 R 10.2 6.3 0.5 117 651.047 R 6.1 0.3 117 655.847 R 6.7 0.4 117 635.973 O 12.3 2.7 0.7 154 651.052 O 4.2 0.8 146 655.838 O 2.7 0.7 146 651.018 V 13.4 4.9 0.2 176 653.955 V 14.8 11.5 0.3 181 653.982 V 14.7 11.5 0.5 183 655.860 V 10.5 0.3 180 657.922 V 7.7 0.4 178 658.000 V 14.0 7.8 0.2 182 657.962 G 14.3 8.5 0.4 179 657.989 G 14.3 9.1 0.5 179 651.023 B 14.4 6.4 0.2 180 653.988 B 15.7 14.0 0.6 186 654.020 B 15.7 15.2 0.6 187 654.039 B 15.7 16.3 0.5 186 655.866 B 13.2 0.3 182 657.955 B 15.2 10.3 0.5 182 657.991 B 15.1 10.8 0.7 180 651.531 U 15.5 12.2 1.6 177 654.004 U 16.3 16.5 3.5 179 657.939 U 16.0 22.9 4.1 188 657.994 U 16.0 21.3 9.4 183 ------------------------------------------------ The most striking feature is a large and fast variability of the degree of polarization. This fast variability is very pronounced in the yellow-ultraviolet spectral region but seems to be absent in the infrared. An extreme example is an increase of the degree polarization by 9 % during only 3 days. Such short time scale of the polarization variability is unprecedented among red variables. It should be noted that the brightness variability is also present with the same time scale and an amplitude of around 1 mag. Smaller variations on a time scale of an hour may be also present but the observations were not accurate enough for establishing it with certainty. The wavelength dependence shows a minimum in the degree of polarization and a rotation of the position angle by almost 90d. Such features were already observed in other red variables like VY CMa, L_2 Pup and V CVn (Dyck et al. 1971). However in 1968 the wavelength dependence was entirely different. It is demonstrated in the Figure where the present observations obtained in 1972 (filled squares) are compared with 1968 observations (open squares) after Kruszewski (1971). The infrared observations from 1967 (open circles) and from 1971 (filled circles) are also plotted after Dyck et al. (1971). CIT 6 is relatively bright in the ultraviolet what indicates that either it has CH characteristics or there is an unresolved hotter component present. I am indebted to Drs. T. Gehrels and K. Serkowski for arranging the observing run with the University of Arizona telescopes and to Drs. G.P. Kuiper and R.J. Weymann for the permission to use the telescopes. A. KRUSZEWSKI Institute of Astronomy Polish Academy of Sciences Warsaw. References: Dyck, H.M., Forbes, F.F., and Shawl, S.J. 1971, Astron.J. 76, 901. [BIBCODE 1971AJ.....76..901D ] Kruszewski, A. 1971. ibid. 76, 576. [BIBCODE 1971AJ.....76..576K ] Lockwood, G.W. 1970, Astrophys.J.Letters 160, L47. [BIBCODE 1970ApJ...160L..47L ] Pesch, P. 1967, ibid. 149, L65. [BIBCODE 1967ApJ...149L..65P ] Wisniewski, W.Z., Wing, R.F., Spinrad, H., and Johnson, H.L. 1967, ibid. 148, L29. [BIBCODE 1967ApJ...148L..29W ] [FIGURE 1]