Deficiencies in the Model for the Celestial Motion of the Cep as Derived from a Goddard/VLBI Series of Pole Offsets From 1979 to 1989

N. Capitaine, B. Caze
1991 International Astronomical Union Colloquium  
AbstractA VLBI series of celestial pole offsets (designated as ERP(GSFC)90 R 01 in the IERS series of Earth Rotation Parameters) spanning 10 years has been used for deriving the corrections to the IAU constant of precession and to the main terms of the 1980 IAU series of nutation using the same method as Herring (1988) for constraining the corrections to the 9.3yr nutation and to the l8.6yr nutation in longitude. The estimated corrections have been found to be − 0.279ʺ/c ± 0.02 ʺ/c (formal
more » ... 02 ʺ/c (formal error) for the IAU constant of precession and +3.13±0.15mas for the 18.6yr nutation coefficient in obliquity. A circular term with a radius of the order of 0.25mas at a period of 430 days has moreover been revealed in the residuals as obtained after applying the estimated corrections to the series. If such a circular term in the celestial motion of the pole is due to the free core nutation, its estimated period would correspond to a core flattening of 2.687×10−3, which is in good agreement with the one of 2.674×10−3corresponding to the estimated amplitude of the retrograde annual nutation.
doi:10.1017/s025292110006382x fatcat:hzy7tkm5rfeupcii6dp6h3fbt4