COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3449

                                            Konkoly Observatory
                                            Budapest
                                            2 April 1990

                                            HU ISSN 0374 - 0676


        R CrB AT THE BEGINNING OF THE VISUAL LIGHT MINIMUM

   During August-September 1988 and February-March 1989 a number of 
polarimetric and photometric observations of R Coronae Borealis at the beginning
of minimum brightness were made using the 60-cm telescope of Soviet-Bolivian
Observatory Santa Ana (Tarija, Bolivia) with the spectrophotopolarimeter
(Bugaenko and Guralchuk, 1985) and the standard UBVR filters. The photometric 
results are given in Table I. Typical photometric errors are 0.01-0.03
mag. The polarimetric observations in the bands U, B, V, R and integral
light (Int.) are given in Table II, where P - percentage polarization, 0 -
position angle and sigma_P, sigma_Theta are their standard errors respectively.
   Colour variations of R CrB at this light minimum are similar to those
observed during the rapid (by rate of brightness decrease) minimum of 1972
(Rao, 1974). This assumes also likeness of other observational characteristics 
at this phase of the brightness curve. Really, wavelength dependence
of polarization (for the first two dates) is comparable to that found for
the minimum of 1972 (Rosenbush, 1986).

                    Table I

   Date,      V      B-V      U-B       V-R
JD 2447000+
   372.53   7.80m   0.53m    -0.16m    0.50m
   379.48   9.78     .37     - .58      .53
   380.56   10.00    .35     - .58      .53


                    Table II

Date          U          B          V          R          Int.
ID 2447000+   P+/-sigma_p,%  P+/-sigma_p,% P+/-sigma_p,% P+/-sigma_p,% 
              P+/-sigma_Theta,deg   P+/-sigma_Theta,deg    P+/-sigma_Theta,deg    P+/- sigma_Theta,deg    P+/-sigma_Theta,deg
              
380.5         2.2+/-.4     2.0+/-.2     1.3+/-.2     1.2+/-.2     -
              110+/-5      107+/-2      110+/-3      92+/-8
381.5         1.0+/-.4     0.8+/-.2     1.4+/-.2     0.3:         -
              106+/-11     96+/-7       102+/-4      91
408.5         -            -            -            -            1.6+/-.2
                                                                  70+/-3
411.5         -            -            2.1+/-.3     -            -
                                        91+/-4
569.9         -            0.46+/-.20   0.57+/-.06   0.63+/-.14   -
                           135+/-12     115+/-3      122+/-6
574.9         -            0.69+/-.14   0.46+/-.06   0.54+/-.14   -
                           122+/-6      125+/-4      127+/-7
.- it is doubtful.


A.E. ROSENBUSH, V.K. ROSENBUSH and D.F. GAYDAY
Main Astronomical Observatory
252127 Kiev
Ukrainian SSR


References:
Bugaenko, O.I. and Guralchuk, A.L.: 1985, in Photometric and Polarimetric
         Investigations of Celestial Bodies (ed. Morozhenko A.V.),
         Kiev, "Naukova Dumka", p.160. [BIBCODE 1985ppic.conf..160B ]
Rao, N.K.: 1974, Ph.D. Thesis. Univ. of California, Santa-Cruz. [BIBCODE 1974PhDT.........5R ]
Rosenbush, A.E.: 1986, Kinematics Phys. Celest. Bodies, 2, 5, p.29. [BIBCODE 1986KFNT....2...29R ]