|Beta Lyrae is an
interacting eclipsing binary with an orbital rotation
period of 12.914-12.941 days, depending upon published
ephemeris source. The large, primary star is a
B6-B8 giant of approximately 3 solar mass. The
primary star has evolved to the point of filling its
Roche Lobe and is spilling over onto the secondary
star. The secondary type B star is considerably
more massive than the primary at 13 solar mass, but is
completely embedded in the thick accretion disk produced
by the incoming matter from the primary star. The
orbit of the binary system is nearly edge on to our line
of sight so both primary and secondary undergo eclipses.
10 spectra have been collected over a 1 month period resulting in a fair orbital phase distribution. I have focused on the region 4200-5200 angstrom as I am able to resolve both blue and red shift absorption of several He I emission lines, clearly showing 'P-Cygni' profiles. All spectra were recorded with an Alpy 600 spectrograph equipped with a 23u off-axis guiding slit and a Atik 420M monochrome CCD camera. Dispersion is 3 Angstrom per pixel, or 554 Angstrom per millimeter. 80mm f/6 APO Stellarvue SV80S on a Losmandy GM8 equatorial mount. A DMK41 USB video camera was used with PHD Autoguiding software for guiding with the off-axis slit. Nebulosity image processing software was used for selecting and processing the .FITs spectra files. Since exposure time was less than 20 seconds for all of the collected spectra, no darks or flats were used. 4-6 frames were stacked for each spectra. Image profiles were produced and calibrated with RSpec software. Spectra of Gamma Lyrae, a B9 III star, were collected as reference star with each Beta Lyrae spectra and used for calibration.
Comparing absorption shifts and line broadening relative to the orbital phase is both fascinating and frustrating. Beta Lyrae has been an enigma since its discovery by John Goodricke in 1784!