COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3433

                                             Konkoly Observatory
                                             Budapest
                                             19 February 1990

                                             HU ISSN 0374 - 0676


         A NEW SUSPECTED POLARIZATIONAL VARIABLE IN CYGNUS

   Two stars, N2 (c1) and N3 (sv-suspected variable) in Fig.1, were used
as comparison stars during the R-band photometry and spectropolarimetry of
the Wolf-Rayet star HD 191765 (WR) in October 1989. The measurements were
carried out with the 0.6m telescope of Mid-Asia expedition of the Main 
astronomical observatory. The N3 star was found to have highly variable first
three Stokes parameters: I, q_R, u_R (Fig.2.). The standard deviation of the
R-band flux ratio F(sv)/F(c1) was sigma_R=3.2%, and simultaneously sigma_R(F(WR)/
F(c1)) = 1.9%. There were one-measurement-accuracies sigma q =0.19%, sigma u=0.21%,
but sigma q (sv)=0.79%, sigma u (sv)=0.60%. There are obvious systematical night-
to-night variations on q,u-plane (Fig.3). The star N3 may be a binary system 
with P > 12d, because on q,u-plane we can see roughly less than a half
of full q,u-locus.

                            [FIGURE 1]

 Fig.1. Finding chart. 1 - HD 191765 (WR) alpha(1950)=20h08m22s delta(1950)=
    36 01'40" ; 2 - BD+35d 4000 (c1); 3 - the suspected variable (sv).

                            [FIGURE 2]

 Fig. 2. The variation of R-band flux and polarization. A) F_R(sv)/F_R(c1);
 b) R_R(WR)/F_R(c1). The variations of the Stokes parameters; c) q%;
 d) u %.

                            [FIGURE 3]

 Fig.3. Polarimetric observations of the suspected variable. Consecutive
  observations (during one night) are joined by a line.


Table I. The observations of the suspected variable



JD          F_R(sv/c1)    p%     q%    sigma q%  u%  sigma u% theta^^d  sigma theta
          
2447800.+
13.101      0.510        0.86   0.86   0.20    0.06   0.22   182.1   9.9
14.098      0.561        1.32   1.32   0.18    0.11   0.21   182.3   6.5
14.201      0.515        1.06   1.01   --      0.32   --     188.8   --
14.278      0.531        1.24   1.16   --      0.42   --     189.9   --
15.098      0.527        0.67   0.59   0.16   -0.32   0.21   165.5   6.0
15.197      0.517        0.77   0.77   -       0.02   -      180.9   --
15.299      0.491        2.38   1.99   --     -1.30   --     163.5   --
16.096      0.525        1.51   0.39   0.17   -1.46   0.18   127.4   6.3
16.192      0.519        0.72   0.47   --     -0.54   -      155.5   --
17.085      0.512        0.54  -0.53   0.16    0.12   0.20    83.6   9.6
17.176      0.520        0.89  -0.17   --     -0.87   --     129.4   --
17.269      0.529        0.85   0.10   --     -0.84   --     131.4   --
18.091      0.494        0.18   0.07   0.24   -0.16   0.26   146.8   11.9
18.190      0.509        1.28  -0.94   --     -0.87   --     111.3   -
18.282      0.504        1.10  -0.54   --     -0.96   --     120.3   --



S. MARCHENKO, A. MOROZHENKO                   V. VINOGLYADOV
Main astronomical observatory of the          Kharkov state university (USSR)
Ukrainian Academy of Sciences (USSR)