Issue |
A&A
Volume 431, Number 2, February IV 2005
|
|
---|---|---|
Page(s) | 721 - 727 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361:20041500 | |
Published online | 04 February 2005 |
Precession from Hipparcos and FK5 proper motions compared with current values: Reasons for discrepancies
Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany e-mail: [s30;s11]@ix.urz.uni-heidelberg.de
Received:
21
June
2004
Accepted:
13
October
2004
The comparison of Hipparcos and FK5 proper motions points to an inconsistency
with the correction, , of the luni-solar precession derived from VLBI
and LLR observations with unprecedented accuracy. An attempt is made to explain
this inconsistency of approximately -1.3 mas/yr by rotational
offsets of the Hipparcos and FK5 proper motion
systems. In terms of right ascension and declination, these offsets give rise
to proper motion offsets in the range of ±1 mas/yr on average which is not
exceptional given the FK5 error budget. In the case of Hipparcos it is
proven that the proper motions are not affected by rotational offsets larger
than those indicated by the errors of the proper motion link to the ICRF. This
result is obtained by analysing the Hipparcos proper motions in view of the
existence of additional systematic motions other than those caused by
galactic rotation and the parallactic motion of stars due to the solar
motion with respect to the LSR. It is concluded that
the Hipparcos proper motions are nearly free of unmodelled rotations,
confirming that the Hipparcos frame is inertial at the accuracy
level of the proper motion link to the ICRF. The gap between the estimated
precessional corrections is bridged primarily by minor changes in
the FK5 proper motions of the order of their errors, and only to a small extent
by the elimination of a bias in the Hipparcos proper motions.
Key words: astrometry / reference systems
© ESO, 2005
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