THE SPECTROSCOPIC ORBIT OF PI-CETI

pi Ceti (HR 811, B7 V) has been known to be variable in its radial vel ocity for almost a century, but its relatively long period and small a mplitude have conspired against a determination of its orbit. We have combined in an optimal fashion observations from early in this century with modern measurements to find the spectroscopic orbit with high ac curacy. The orbit has a period of 7.45 years and a semiamplitude of 4. 3 km/s. The measured eccentricity of e=0.00+/-0.07 is indistinguishabl e from circular, surprising for such a long period. The 76 radial velo city observations available extend over 12 cycles of the orbit. (C) 19 97 American Astronomical Society.