Hipparcos New Reduction: The Astrometric Catalogue

‘Hipparcos, the new Reduction of the Raw data’ (van Leeuwen 2007a).

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.

Note that the covariance matrix is stored in a rather obscure form in this catalogue. The way to reconstruct it from the existing fields is described in Appendix B of Michalik et al. (2014).

Columns description:

Hipparcos identifier

Entry in one of the supplementary 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 ra_rad

Formal error on de_rad

Formal error on parallax

Formal error on pm_ra

Formal error on pm_de

Percentage rejected data

Goodness of fit

Number of components

Number of field transits used

Upper-triangular weight matrix element 3; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

$$\left(\begin{array}{ccccc}\hfill {U}_{1}\hfill & \hfill {U}_{2}\hfill & \hfill {U}_{4}\hfill & \hfill {U}_{7}\hfill & \hfill {U}_{11}\hfill \\ \hfill 0\hfill & \hfill {U}_{3}\hfill & \hfill {U}_{5}\hfill & \hfill {U}_{8}\hfill & \hfill {U}_{12}\hfill \\ \hfill 0\hfill & \hfill 0\hfill & \hfill {U}_{6}\hfill & \hfill {U}_{9}\hfill & \hfill {U}_{13}\hfill \\ \hfill 0\hfill & \hfill 0\hfill & \hfill 0\hfill & \hfill {U}_{10}\hfill & \hfill {U}_{14}\hfill \\ \hfill 0\hfill & \hfill 0\hfill & \hfill 0\hfill & \hfill 0\hfill & \hfill {U}_{15}\hfill \end{array}\right)$$ |

on the astrometric parameters RA, Dec, parallax, proper motion in RA, proper motion in Dec (in the case of 5-parameter solutions as above)
and derivatives of those proper motion components (in the case of 7- and 9-parameter solutions).

Upper-triangular weight matrix element 4; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 5; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 6; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 7; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 8; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 9; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

[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; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 2; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 10; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 11; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 12; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 13; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 14; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

Upper-triangular weight matrix element 15; see Hipparcos, the New Reduction of the Raw data, Appendix C (van Leeuwen, 2007).

The upper-triangular weight matrix U is related to the covariance matrix C by

$${\mathrm{C}}^{-1}={\mathrm{U}}^{T}\mathrm{U}$$ |

and the elements ${U}_{i}$ forming the upper triangular matrix are indexed as

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