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Preliminary Orbits from Velocities with the CCD-Echelle Spectrometer at Lick
Published online by Cambridge University Press: 12 April 2016
Extract
The Hamilton CCD-echelle spectrometer at the coudé focus of the 3-m Shane telescope of the Lick observatory has been described by Vogt (1987). Illustrations of some binary star spectra obtained with this instrument are given by Popper & Nelson (1990, B-type binaries with large magnitude differences) and by Popper (1992, G-type eclipsing binaries), where typical cross-correlation functions are also shown.
In this progress report, I give some initial preliminary orbital results. First is the bright early B binary, VV Ori, the orbits of which have been the subject of considerable controversy (Duerbeck 1975, Andersen 1976, Popper 1981). According to Chambliss & Leung (1982) and to the line ratios, the secondary component contributes about 10% of the light of the system in the visual region. Multiple (2 to 4) exposures of VV Ori have been obtained with the Hamilton on 7 nights. Velocities of the primary are determined from 13 lines, primarily of OII and HeI between 440 and 590 nm. The only lines found to be useful for the secondary are HeI 597.5 and 492.1. Analysis of the velocities is complicated by the poorly determined variation of the center-of-mass velocity, with a range of roughly 26 km s−1 and a period of roughly 120 days (e.g., Duerbeck 1975). Preliminary orbits based on this material lead to masses 11.1 and 4.7.M⊙, to be compared to Duerbeck’s values of 7.7 and 3.4. It is primarily the high signal/noise ratio, over 600, that enables this study to be carried out satisfactorily.
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- Spectroscopic Studies
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- Copyright © Astronomical Society of the Pacific 1992