Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981a%26a....99..274j&link_type=abstract
Astronomy and Astrophysics, vol. 99, no. 2, June 1981, p. 274-284. Research supported by the Conselho Nacional de Pesquisas of
Astronomy and Astrophysics
Astrophysics
33
B Stars, Helium, Stellar Spectra, Stellar Spectrophotometry, X Ray Sources, X Ray Spectroscopy, Balmer Series, Hertzsprung-Russell Diagram, Line Spectra, Ubv Spectra
Scientific paper
Photometric and spectroscopic observations are presented of the Be star He 3-640, the proposed optical counterpart of the X-ray transient A1118-61. Investigations carried out in March 1976 and February and March 1977 at the European Southern Observatory in Chile are discussed and earlier data is re-analyzed. Magnitudes and colors have remained practically constant from April 1975 to January 1980; the overall tendency in observed color changes is to move perpendicular to the reddening line, and the spectrum is typical of a fast-rotating Be star with an extended envelope. He 3-640 is calculated to be at a distance of 5 plus or minus 2 kpc with a total emission along the B-V line of approximately 1.2. Balmer velocities indicate the presence of turbulent motions within the envelope with a time scale of a few days. It is suggested that the direct interaction of a compact object with the Be envelope may play a role in the production of X-rays. Typical density tracings and rectified spectra of He 3-640 are given, as are velocity variations of the Balmer emission lines and radial velocity-excitation plots.
Chevalier Clément
Ilovaisky Sergio A.
Janot-Pacheco Eduardo
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