Rediscussion of Eclipsing Binaries. XVIII. Faint Secondaries in the Spectra of Early B-Type Systems
Abstract
Spectra of 3 early B-type eclipsing binaries, for which velocities of faint secondary components have been reportedly measured on photographic spectrograms, have been observed with high resolution and signal-to-noise ratio. The equipment employed is the echelle-CCD Hamilton spectrometer on the 3 m Shane telescope of the Lick Observatory. Very provisional orbits have been re-derived for the secondaries in two of the systems, VV Ori, a main-sequence system, and V380 Cyg, with a highly evolved BO primary, principally on the basis of velocities from the He I line, lambda-5876. Lines in the secondaries of these systems are considerably weaker than previously thought, the 5876 line have equivalent widths of 0.07 A and 0.024 A in VV Ori and V380 Cyg, respectively. No line of the secondary was detected unequivocally in the spectrum of the third system, V1765 Cyg, which also has an evolved early B-type primary. The 5876 line is weaker than 0.03 A. An unseen third body causes a variation of the velocity of the center of mass of the close binary in VV Ori, which is poorly determined. VV Ori would otherwise be a promising system for the determination of fundamental stellar properties, its masses being roughly 11 and 4.5 solar masses. V380 Cyg has the nearly unique potential of providing the mass and other properties of an evolved early B star, type B1.5 II-III. The principal difficulty in achieving this aim is in removing the indeterminacy of the solution of the light curve, with its shallow minima and eccentric orbit. Some discrepancies are found between theoretical and observed strengths of He lines in the spectra of early B-type stars of high luminosity. (SECTION: Stars)
- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- July 1993
- DOI:
- 10.1086/133223
- Bibcode:
- 1993PASP..105..721P
- Keywords:
-
- B Stars;
- Eclipsing Binary Stars;
- Faint Objects;
- Stellar Spectra;
- Charge Coupled Devices;
- Light Curve;
- Spectral Line Width;
- Stellar Evolution;
- Stellar Luminosity;
- Stellar Spectrophotometry;
- Astronomy;
- BINARIES: ECLIPSING;
- STARS: EARLY-TYPE