Astrometric-spectroscopic determination of the absolute masses of the HgMn binary star Phi Herculis

Abstract

The Mercury-Manganese star Phi Her is a well known spectroscopic binary that has been the subject of a recent study by Zavala et al. (2006), in which they resolved the companion using long-baseline interferometry. The total mass of the binary is now fairly well established, but the combination of the spectroscopy with the astrometry has not resulted in individual masses consistent with the spectral types of the components. The motion of the center of light of Phi Her was clearly detected by the Hipparcos satellite. Here we make use of the Hipparcos intermediate data (`abscissa residuals') and show that by combining them in an optimal fashion with the interferometry the individual masses can be obtained reliably using only astrometry. We re-examine and then incorporate existing radial-velocity measurements into the orbital solution, obtaining improved masses of 3.05 +/- 0.24 M_Sun and 1.614 +/- 0.066 M_Sun that are consistent with the theoretical mass-luminosity relation from recent stellar evolution models. These mass determinations provide important information for the understanding of the nature of this peculiar class of stars.

arXiv commentTotal of 18 pages including figures and tables, in emulateapj format. To appear in The Astronomical Journal, June 2007 issue

References in corpus (5)

• Towards Better Age Estimates for Stellar Populations: The Y^2 Isochrones for Solar Mixture
• Re-processing the Hipparcos Transit Data and Intermediate Astrometric Data of spectroscopic binaries. I. Ba, CH and Tc-poor S stars
• Astrometric orbits of SB9 stars
• Neon abundances in normal late-B and mercury-manganese stars
• The HgMn Binary Star Phi Herculis: Detection and Properties of the Secondary and Revision of the Elemental Abundances of the Primary

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