EG ANDROMEDAE: A NEW ORBIT AND ADDITIONAL EVIDENCE FOR A PHOTOIONIZED WIND

We analyze a roughly 20 yr set of spectroscopic observations for the symbiotic binary EG And. Radial velocities derived from echelle spectra are best fit with a circular orbit having an orbital period of P = 483.3 +/- 1.6. days and semi-amplitude K = 7.34 +/- 0.07 km s(-1). Combined with previous data, these observations rule out an elliptical orbit at the 10 sigma level. Equivalent widths of H I Balmer emission lines and various absorption features vary in phase with the orbital period. Relative to the radius of the red giant primary, the apparent size of the H II region is consistent with a model where a hot secondary star with effective temperature T-h approximate to 75,000 K ionizes the wind from the red giant.