COMMISSION 27 OF THE I.A.U.
      INFORMATION BULLETIN ON VARIABLE STARS
                   NUMBER 109


                                        Konkoly Observatory
                                        Budapest
                                        20 October 1965

            SPECTRAL VARIATIONS OF THE
                 WR STAR HD 50896 

Variations in the spectrum of the WN6 star HD 50896 were
found by Wilson (1948), Smith (1955) and by one of us (Bertola
1963), while light variations were detected by Ross (1961). Fifty
spectra were obtained at Asiago using the Cassegrain spectrograph
40 A/mm at Hgamma in order to ascertain the possible binary nature of
the star, common to a large number of WR stars. The spectra cover
a period of six years, from 1959 to 1965. Many of them were taken
in rapid succession during the night. The following emission lines
have been measured for radial velocity: He II 4859, 4685, 4541,
4338, 4199, 4100; N IV 4058; N V 4603-19. For all the lines 
comparable radial velocity variations with a mean amplitude of
300 km/sec were detected. On the average the velocity range is
between -20 km/sec and +280 km/sec.  However, no correlation seems
to exist between the displacements of the lines. A period-analysis
of the radial velocities shown by the N V 4603-19 line, the sharpest
feature in the spectrum, leads to a tentative period less than one
day. Nevertheless the scatter is high and no certain conclusion can
be derived. We are tempted to conclude that on the basis of our
present data, the hypothesis of the binary nature of the star has
to be ruled out. The fact that the continuum in  HD 51896 is not so
strong as in other WR binaries, where there is the contribution of
the companion, might be another argument  supporting the above
conclusion.


   An additional aspect of the spectral variations of HD 50896
is concerning the line profiles of He II 4100 and N IV 4058. While
in the majority of the spectra the contour of the He II 4100 line
is rounded, in some cases it exhibits a plateau-like shape. More
conspicuous are the variations of N IV 4048. Normally the profile
of this line is asymmetric, steeper on the violet edge. However,
sometimes the band has a superimposed absorption feature, whose
position and intensity are variable. When the absorption is present,
the red edge is equally steep as the violet.


   If future observations will confirm that HD 50896 is not
a binary system, then, the above variations are an indication of
considerable activity in the envelopes of WR stars.




References:

Bertola F., 1963, Asiago Contr. No. 137,
Ross L. W., 1961, PASP 73, 354. [BIBCODE 1961PASP...73..354R ]
Smith H. J., 1955, Harvard Thesis. [BIBCODE 1955PhDT.........2S ]
Wilson O. C., 1948, PASP 60, 383 [BIBCODE 1948PASP...60..383W ]

Asiago Astrophysical Observatory


                                   R. BARBON
                                   F. BERTOLA
                                   F. CIATTI
                                   R. MARGONI