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[107.15] Detection of the Secondary of the HgMn star Phi Herculis with the Navy Prototype Optical Interferometer.

R. T. Zavala (USNO), C. A. Hummel (ESO), J. T. Armstrong (NRL), J. A. Benson, D. J. Hutter, K. J. Johnston (USNO), T. A. Pauls (NRL)

Phi Herculis is a Mercury-Manganese star with an extensive history of observation and theoretical analysis. It is a relatively bright (v=4.2) single lined spectroscopic binary. The secondary star has never been directly detected with traditional photometric or spectroscopic techniques. Using the superb angular resolution of the Navy Prototype Optical Interferometer (NPOI) we have directly detected the secondary of Phi Herculis. We present an astrometrically determined orbit of the binary system using 7 years of observations with the NPOI. The magnitude difference (secondary - primary) is 2.64 in V and 2.62 in R. This magnitude difference implies that the secondary has a spectral type of A9, if it is a main sequence star. These observations showcase the NPOI's capability to accurately determine the parameters of single-lined spectroscopic binaries,which previously were at the mercy of an unknown orbital inclination.

The author(s) of this abstract have provided an email address for comments about the abstract: bzavala@nofs.navy.mil

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.