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J. A. Harvin, D. R. Gies (Georgia State University), L. R. Penny (College of Charleston)
Delta Orionis is a massive triple star system consisting of a close spectroscopic binary and a distant tertiary star. Using cross-correlation methods with 59 IUE spectra, we have for the first time measured the secondary star's reflex motion. The mass ratio is q=m2/m1=0.54 ±0.03. We present revised orbital elements that generally agree with those presented by Harvey et al. (1987, The Observatory, 107, 205) based on 44 IUE spectra. Our period is 5.73261 ± 0.00001 days. Harvey et al. also give a series of previous orbital element determinations for delta Orionis, starting in 1902 and continuing through 1982, which they conclude are consistent with apsidal periods between 216 and 227 years and our results agree. In spite of the caution expressed in Harvey et al., we believe that the variation in gamma velocity seen over the past century is the reflex motion of the central binary in its orbit about the center of mass of the binary-tertiary system. In support of our opinion, we find a gamma velocity that is significantly higher than the previous determinations.
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The author(s) of this abstract have provided an email address for comments about the abstract: harvin@chara.gsu.edu