Tomographic separation of composite spectra. I - The components of Plaskett's Star

• Published in: The Astrophysical journal Vol. 385; no. 2; pp. 708 - 717
• Main Authors: Bagnuolo, William G., Jr, Gies, Douglas R., Wiggs, Michael S.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 01.02.1992
• Subjects: Astronomy; Astrophysics; Binary and multiple stars; Earth, ocean, space; Exact sciences and technology; Spectroscopic binaries. Close binaries; Stars; Primary component; Ultraviolet radiation; Correlation analysis; Physical parameter; Spectroscopic binary; Cross correlation; Ultraviolet spectrum; Spectral type; Radial velocity; Spectral classification; Secondary component; Physical properties
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/170977

The UV photospheric lines of Plaskett's Star (HD 47129), a 14.4 day period, double lined O-type spectroscopic binary were analyzed. Archival data from IUE (17 spectra well distributed in orbital phase) were analyzed with several techniques. A cross correlation analysis, which showed that the secondary produces significant lines in the UV, indicates that the mass ratio is q = 1.18 +/- 0.12 (secondary slightly more massive). A tomography algorithm was used to produce the separate spectra of the two stars in six spectral regions. The interpolated spectral classifications of the primary and secondary, 07.3 I and 06.2 I, respectively, were estimated through a comparison of UV line ratios with those in spectral standard stars. The intensity ratio of the stars in the UV is 0.53 +/- 0.05 (primary brighter). The secondary lines appear rotationally broadened, and the projected rotational velocity V sin i for this star is estimated to be 310 +/- 20 km/s. The possible evolutionary history of this system is discussed through a comparison of the positions of the components and evolutionary tracks in the H-R diagram.