COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 1124

                                   Konkoly Observatory
                                   Budapest
                                   1976 April 6


 CONCERNING THE RELATIVE MAGNITUDES OF THE SS CYGNI COMPONENTS



      Presented here is a small sample of standardized UBV 
observations of SS Cygni, made with the 24-inch photometric reflector
of Lick Observatory when SS Cygni was at minimum. For this sample   
 V_av = 11.66; (B-V)_obs_av.= +0.53 +- 0.05.

        JD_hel     V           B-V           U-B

   2442550.962   11.62+-0.03   0.52+-0.02   -0.70+-0.03
      2551.935   11.70         0.50         -0.83
      2577.973   11.63         0.41         -0.78
      2578.977   11.60         0.53         -1.08
      2579.973   11.76         0.71         -1.00

      Joy (1956) states that the system consists of a dG5  star
and a sdBe companion, and that the absolute magnitudes of the
two stars are equal.
      If one considers a model SS Cygni system consisting of a
dG5 star with B-V = +0.70 and a white dwarf companion with B-V=
-0.10, at a distance of 270 pc, with  a(r) = 1 mag/kpc and  R=
A_V/E(B-V) = 3(giving E (B-V)= 0.09 mag), then the combined light
of the two stars can give an observed (reddened) B-V of +0.53
only if the white dwarf is 1.2 magnitudes fainter in V than the
main sequence star. With an absolute visual magnitude of +5.1
for the primary, the combined M_v = +4.8 is consistent with the
value derived with the formula M_V = m_V + 5- 5log(r) + A_V, with
m_V = 11.66, r = 270 pc, and A_V = 0.27 mag. An uncertainty  of
+-0.05 mag in the observed B-V results in an uncertainty of +-0.8
mag for the visual magnitude difference between the stars.
    We may conclude that the hot component of the SS Cygni 
system is probably fainter in V than its main sequence companion,
by about one magnitude.



                            K. KRISCIUNAS
                         903 Edgewater Drive
                         Naperville, Illinois
                              U.S.A.

Reference:
Joy, A.H. 1956, Ap. J. 124, 317 [BIBCODE 1956ApJ...124..317J ]