Hipparcos New Reduction: The Astrometric Catalogue

Hipparcos, the new Reduction of the Raw data van Leeuwen F. Astron. Astrophys. 474, 653 (2007) http://dx.doi.org/10.1051/0004-6361:20078357

A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming accuracies for nearly all stars brighter than magnitude Hp=8 to be better, by up to a factor 4, than in the original catalogue. The new Hipparcos astrometric catalogue is checked for the quality of the data and the consistency of the formal errors as well as the possible presence of error correlations. The differences with the earlier publication are explained. Methods. The internal errors are followed through the reduction process, and the external errors are investigated on the basis of a comparison with radio observations of a small selection of stars, and the distribution of negative parallaxes. Error correlation levels are investigated and the reduction by more than a factor 10 as obtained in the new catalogue is explained. Results. The formal errors on the parallaxes for the new catalogue are confirmed. The presence of a small amount of additional noise, though unlikely, cannot be ruled out. Conclusions. The new reduction of the Hipparcos astrometric data provides an improvement by a factor 2.2 in the total weight compared to the catalogue published in 1997, and provides much improved data for a wide range of studies on stellar luminosities and local galactic kinematics.

Columns description:

Hipparcos identifier

Entry in one of the suppl.catalogues

Right Ascension in ICRS, Ep=1991.25

Declination in ICRS, Ep=1991.25

Right Ascension in ICRS, Ep=1991.25

Declination in ICRS, Ep=1991.25

Parallax

Proper motion in Right Ascension

Proper motion in Declination

Formal error on RArad

Formal error on DErad

Formal error on Plx

Formal error on pmRA

Formal error on pmDE

Percentage rejected data

Goodness of fit

Number of components

Number of field transits used

Upper-triangular weight matrix element 3

The upper-triangular weight matrix U is related to the
covariance matrix C by
C-1 = â¼U U (â¼U represents transposed U)
The elements Ui forming the upper triangular matrix are stored as
Â± -+
— (1) (2) (4) (7) (11) —
— 0 (3) (5) (8) (12) —
— 0 0 (6) (9) (13) —
— 0 0 0 (10) (14) —
— 0 0 0 0 (15) —
Â± -+
on the astrometric parameters RA, Dec, plx, pmRA, pmDE,
and derivatives of proper motions for 7- and 9-parameter
solutions.

Upper-triangular weight matrix element 4

Upper-triangular weight matrix element 5

Upper-triangular weight matrix element 6

Upper-triangular weight matrix element 7

Upper-triangular weight matrix element 8

Upper-triangular weight matrix element 9

[0,159] Solution type new reduction

The solution type is a number 10xd+s consisting of two parts d and s:
- s describes the type of solution adopted:
1 = stochastic solution (dispersion is given in the ’var’ column)
3 = VIM solution (additional parameters in file hipvim.dat)
5 = 5-parameter solution (this file)
7 = 7-parameter solution (additional parameters in hip7p.dat)
9 = 9-parameter solution (additional parameters in hip9p.dat)
- d describes peculiarities, as a combination of values:
0 = single star
1 = double star
2 = variable in the system with amplitude ¿ 0.2mag
4 = astrometry refers to the photocenter
8 = measurements concern the secondary (fainter) in the double system

[0,5] Solution type old reduction

as follows:
0 = standard 5-parameter solution
1 = 7- or 9-parameter solution
2 = stochastic solution
3 = double and multiple stars
4 = orbital binary as resolved in the published catalog
5 = VIM (variability-induced mover) solution

Cosmic dispersion added (stochastic solution)

Upper-triangular weight matrix element 1

Upper-triangular weight matrix element 2

Upper-triangular weight matrix element 10

Upper-triangular weight matrix element 11

Upper-triangular weight matrix element 12

Upper-triangular weight matrix element 13

Upper-triangular weight matrix element 14

Upper-triangular weight matrix element 15

Hipparcos magnitude

Colour index

V-I colour index

Error on mean Hpmag

Formal error on colour index

Scatter of Hpmag

[0,2] Reference to variability annex