COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3057


                                            Konkoly Observatory
                                            Budapest
                                            3 August 1987

                                            HU ISSN 0374-0676


              DETECTION OF A NEW Be STAR - gamma Lup

  It is accepted in astronomical community that Be stars may be defined as
non-supergiant early type stars showing Balmer emission lines in their spectra
( Slettebak, 1979 ). Origin of the emission lines is from the extended gaseous
envelopes surrounding the atmosphere of the central object. In general most of
the Be stars are rapid rotators and they show irregular variability both 
spectroscopically and in magnitude. Line emitting envelope around the Be star may
disappear for a long period of time, leaving the central star and the spectrum
of the central star apparently looks like a normal absorption-line B-type 
spectrum. So, with this picture in mind, a Be star may be regarded as B-type star
surrounded by gaseous envelope and the envelope has formed due to the material
ejection from the central star or by mass transfer from a hypothetical companion
in the suspected binary system. Now the question is that whether all B-type
stars will become Be stars or not. If not all, what type of B stars are able
to form gaseous envelope around it? Another information is essential in finding
the elusive cause(s) for the Be phenomenon is that the time scale required
for a star to make a transition from a normal B star to a Be star. Thus the
study of the spectrum of a star which is in transition from a B-type to a Be
star may provide important information for many major unsolved questions of Be
phenomenon. Here we present a new spectrum of gamma Lup (HR 5776, HD 138690, B2 IV,
v sini = 320 km/s ) which was a B-type star with rapid rotation. Spectroscopic
observations of gamma Lup in the H-alpha region were obtained on 22-25 March 1987 with
the Bhavanagar spectrograph using a grating of 1800 grooves/mm at the Cassegrain
focus of the 0.75 m reflector of Vainu Bappu Observatory, Kavalur, India. The
reciprocal dispersion at H-alpha is 16 A/mm on 09802 emulsion. Obtained spectra
of H-alpha profiles are shown in Fig 1. In Fig. 1 the vertical arrows show the
emission peaks within the absorption profile of H-alpha. In the H-alpha profile of gamma Lup
we find two to three emission peaks. Different peaks of central reversal of
emission may be due to self-absorption of line radiation in the circumstellar
envelope. The width of the H-alpha profile is very broad which may be due to strong
electron scattering in the envelope. The wavelengths of different emission


                              [FIGURE 1]

 Fig. 1. Spectra of gamma Lup in the H-alpha region. Data of observations 
 have been mentioned along with each spectrum. Wavelength decreases along 
 the right hand side i.e. towards the arrow mark. Vertical arrow marks 
 indicate the peak point of the emission. All spectra have been expressed 
 in terms relative density.


peaks are greater than 6562.817 A which indicates the material flow away
from the line of sight of the observer to the star. This material flow may
be mainly due to the mass ejection from the central star. At present we believe
that high rotational velocity of gamma Lup has played the important role 
for the material ejection from the star. This early type star which has
undergone a transition from a B-type to Be may give a lot of important 
information for understanding the unsolved problems of Be phenomenon. Continued
regular observation of this star is suggested.


                  K. K. GHOSH, K. KUPPUSWAMY, K. JAYKUMAR
                        M. J. ROSARIO, and C. VELU
            Indian Institute of Astrophysics, Vainu Bappu Observatory
               Kavalur, Alangayam, N. A., T. N. 635701, INDIA



Reference:
Slettebak, A. : 1979, Space Sci. Rev., 23, 541. [BIBCODE 1979SSRv...23..541S ]