COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3508

                                               Konkoly Observatory
                                               Budapest
                                               21 August 1990

                                               HU ISSN 0374 - 0676


              THE UTLTRAVIOLET SPECTRUM
           OF CLOSE BINARY STAR V448 CYGNI

  The ultraviolet spectrum of V445 Cygni was obtained on July
25, 1982, using the IUE SWP 1746 camera in the range from 1165
Angstrom to 2126 Angstrom, with the resolution ~6 A (see Fig.1)
at the phase of orbital period 0p.74. Because of low resolution,
the spectra of primary and secondary components were not
separated, despite in optics it is possible at this phase
(Glazunova, 1987).
   For comparison with the models of Kurucz (1979), the 
interstellar absorption was taken into account by using the known
dependence of X_Lambda from E(Lambda-V)/E(B-V) relationship
(Nandy et al. ,1975 ), where the value of color excess E(B-V)=0.67m
for V448 Cygni was used (Hiltner, 1956). The main parameters of the
model of Kurucz were derived by Glazunova (1987): T_eff=20000 K,
lg g = 3 for the primary; and T_eff=30000 K, lg g = 4 for the
secondary, respectively. Continuum fluxes, obtained by using the
programs of Kurucz (1979) in LTE-approximation, were summarized
for both components. The parameters of components obtained in
the optical range are describing the binary system's
UV-spectrum rather well (Fig. 2).
   The identification of the absorption lines was made by
comparing with the synthetic spectrum (Kurucz, 1979). The
strong resonance lines such as Ly_Alpha, CIV 1550, SiIV 1394-1403,
and strong lines CII 1335, SiIII 1206, SiIII 1298-1304, NIV
1718, as well as a set of Fe lines, in various ionization
stages were identified. From Howarth and Raman (1989), one may
obtain the mass loss rate in lines of these ions.


                      [FIGURE 1]
                      [FIGURE 2]
                      [FIGURE 3]


         Ion      Mdot (M_Sun/yr)

         C3+      10^-9.9+-0.5
         N4+      10^-9.6+-0.5
         Si3+     10^-9.3+-0.5

   The total mass loss rate by stellar wind for V448 Cygni is
~10^-7.1+-0.5 M_sun/yr
   Besides that, we studied the data for some absolute fluxes
in the UV range for V448 Cygni measured in 1978 by the Sky
Survey Telescope aboard the ESRO satellite TD-1 (Catalogue of
Stellar Ultraviolet Fluxes, 1978).


Wavelength , Angstrom          2740   2365   1965   1565

Flux, E*10^-12
erg/(cm2*s*Angstrom)           2.63   2.24   3.62   3.61

Error
E*10^-12erg/(cm2*s*Angstrom)   0.26   0.41   0.69   0.41


  In Fig.3 one may compare the UV-fluxes (corrected for the
interstellar absorption), from TD-1, with the models of Kurucz.
Empirical and theoretical energy distributions in the spectrum
of V448 Cygni are normalized to the flux at Lambda2365. One may
see the depressions of the continuum from 1565 Angstrom to 1965
Angstrom and from 2400 Angstrom to 2800 Angstrom. The range of
LambdaLambda 2400-2800 Angstrom was used to estimate the
circumstellar envelope parameters while assuming the outstanding
additional absorption in numerous UV-lines. The mean depression
value was D=0.307m, and the parameters of two envelope models
computed by Jafarli and Lyubimkov (1988), are:

      a) T_s = 10^4 K, Ne = 10^12 cm^-3, R_s = 1.23*R_*;

      b) T_s = 10^4 K, Ne = 10^11 cm^-3, R_s = 30*R_*.



                                            GALINA V. VOLKOVA

                                            Astronomical Obs.
                                            Odessa State Univ.
                                            Odessa, USSR.


References:

Catalogue of Stellar Ultraviolet Fluxes, 1978 / A compilation
       of absolute stellar fluxes measured by the Sky Survey
       Telescope (S2/68) aboard the ESRO satellite TD-1 /.
Glazunova, L.V.: 1987, PhD Thesis, Odessa State University.
Hiltner, W.A.: 1956, Astrophys. J. Suppl. Ser. 2, 24, 389. [BIBCODE 1956ApJS....2..389H ]
Howarth, I., Prinja Raman, K.: 1989, Astrophys. J. Suppl. Ser.
       69, 3, 527. [BIBCODE 1989ApJS...69..527H ]
Jafarli, A., Lyubimkov, L.: 1988, Izvestiya KrAO, 80, 18.
Kurucz, R.L.: 1979, Astrophys. J. Suppl. Ser. 40, 1. [BIBCODE 1979ApJS...40....1K ]
Nandy, K., Thomson, G.I., Jamar, C., Monfils, A., Wilson, R.:
       1975, Astron. Astrophys. 44, 195. [BIBCODE 1975A&A....44..195N ]