SPECTROSCOPIC BINARY ORBITS FROM PHOTOELECTRIC RADIAL-VELOCITIES

Citation
Rf. Griffin et A. Duquennoy, SPECTROSCOPIC BINARY ORBITS FROM PHOTOELECTRIC RADIAL-VELOCITIES, Observatory, 113(1113), 1993, pp. 53-69
Citations number
38
Journal title
ISSN journal
00297704
Volume
113
Issue
1113
Year of publication
1993
Pages
53 - 69
Database
ISI
SICI code
0029-7704(1993)113:1113<53:SBOFPR>2.0.ZU;2-Q
Abstract
The F2 supergiant HDE 258878 has recently been found to undergo deep e clipses, with a periodicity Of 3 1/2 years. Its companion must be larg e but of relatively low surface brightness. We have been able to measu re the radial velocities of both components, which prove to be in a qu ite eccentric orbit whose period and character agree with the eclipse timings. The primary star is considerably more massive than its compan ion, but both masses are large, 6 and 4 M. respectively. Photometric m odelling of the eclipses shows that the radii of the components are 30 R. (primary) and 35 R. (secondary). Spectral lines of the secondary, probably including the lithium line, have been detected in the red. Th e stars are concluded to have types near to F2 Ib-II and G8 IIb, with absolute magnitudes of -3m.6 and -1m.9 respectively. The distance of t he system, estimated at 1.6 kpc, could be determined with certainty if the angular separation of the components could be measured, as may be come possible by optical interferometry quite soon. A series of occult ations by the Moon will take place in 1995-97, but their circumstances are generally unfavourable for critical studies with high time-resolu tion. Both stars appear to be rotating faster than would correspond to orbital pseudo-synchronization.