The new orbital elements and properties of ε Persei

A detailed analysis of a large collection of electronic spectra from three observatories, together with radial velocities published earlier, were used to derive a new ephemeris and improved orbital elements for the epsilon Per binary. Observations covering a time interval of about 37000 days (101.3 years) can be reconciled with a constant orbital period of 14 super(d).06916 plus or minus 0 super(d).00004. The high orbital eccentricity of 0.555 plus or minus 0.009 was also confirmed. New spectral observations confirm that there is a periodic variation of the systemic velocity. Together with new evidence from astrometric observations (also analyzed here), they confirm the existence of a third body in the system with an orbital period of about 9600 days (26.3 years), rather than 4156 days, as reported earlier. Application of the disentangling technique to the H alpha spectra with good S/N ratios did not allow detection of spectral lines of either the secondary or tertiary components. For plausible inclinations between 30 degree and 90 degree , the observed mass function implies a mass of the secondary M sub(2) = 0.85-1.77 M sub( ), if a primary mass is adopted of 13.5 plus or minus 2.0 M sub( ). Attempts to detect the third body via interferometric observations should continue in spite of this first negative result.