Spectroscopy of EG And over roughly 14 years

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+/-0.07km/s. Combined with previous data, these observations rule out an elliptical orbit at the 10{sigma} level.

Equivalent widths of HI 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_~75000K ionizes the wind from the red giant.