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## HIPNEWCAT - Hipparcos New Astrometric Catalog |
HEASARC Archive |

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 catalog is explained. The formal errors on the parallaxes for the new catalog are confirmed. The presence of a small amount of additional noise, though unlikely, cannot be ruled out.

The new reduction of the Hipparcos astrometric data provides an improvement by a factor 2.2 in the total weight compared to the Hipparcos catalog published in 1997, and, according to the author, provides much improved data for a wide range of studies on stellar luminosities and local galactic kinematics.

Note that this catalog version is slightly different from the one published in the book, as an error that sometimes affected the goodness of fit value for the solution was corrected. The first version of these data archived at the CDS (between June and 15 September 2008) also contained errors which were corrected after this date.

Hipparcos, the New Reduction of the Raw Data van Leeuwen F. <Astron. Astrophys. 474, 653 (2007)> =2007A&A...474..653V Hipparcos, the New Reduction of the Raw Data van Leeuwen F. <Astrophysics & Space Science Library, Vol. 350> =2007ASSL..350.....V The Hipparcos Catalogue Perryman, M.A.C. et al. <Astron. Astrophys. 323, L49 (1997)> =1997A&A...323L..49P

**HIP_Number**

The Hipparcos source
number or identifier, as in the original Hipparcos Catalog.

**Name**

The name of the star in the recommended format for Hipparcos
stars, as created by concatenating the prefix 'HIP ' and the Hipparcos source
number or identifier, as in the original Hipparcos Catalog.

**New_Solution_Type**

The solution type in the new reduction.
This is number between 0 and 115, 10 x d + s, consisting of two parts d and s
where s describes the type of solution adopted as follows:

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)where the above-mentioned files can be found at http://cdsarc.u-strasbg.fr/ftp/cats/I/311/, and d describes the presence of peculiarities, as a combination of values, as follows:

0 = single star 1 = double star 2 = variable in the system with amplitude > 0.2 mag 4 = astrometry refers to the photocenter 8 = measurements concern the secondary (fainter) in the double system

**Old_Solution_Type**

The solution type in the old reduction. This is number
between 0 and 5, 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

**Number_Components**

The number of stellar components.

**RA**

The Right Ascension of the star in the selected equinox for epoch
1991.25. This was given in the ICRS reference system (similar but not
identical to J2000 equator) in the original published catalog (thus
the HEASARC recommends that equinox 2000 should be specified to avoid
inaccuracies due to the non-rigorous HEASARC coordinate precession algorithm)
and in radians, to a precision of 10^{-10} radians.

**Dec**

The Declination of the star in the selected equinox for epoch
1991.25. This was given in the ICRS reference system (similar but not
identical to J2000 equator) in the original published catalog (thus
the HEASARC recommends that equinox 2000 should be specified to avoid
inaccuracies due to the non-rigorous HEASARC coordinate precession algorithm)
and in radians, to a precision of 10^{-10} radians.

**LII**

The Galactic Longitude of the star.

**BII**

The Galactic Latitude of the star.

**Parallax**

The stellar trigonometric parallax, pi, in units of
milliarcseconds (mas): thus to calculate the stellar distance D in parsecs,
D = 1000/pi. The estimated parallax
is given for every star, even if it appears to be insignificant or negative.

**PM_RA**

The proper motion component in the RA direction expressed in
milliarcseconds per Julian year (mas/yr), and given with respect to the
ICRS reference system.

**PM_Dec**

The proper motion component in the Declination direction expressed
in milliarcseconds per Julian year (mas/yr), and given with respect to the
ICRS reference system.

**RA_Error**

The formal error in the Right Ascension given at the
catalog epoch, J1991.25, and expressed in milliarcseconds.

**Dec_Error**

The formal error in the Declination given at the
catalog epoch, J1991.25, and expressed in milliarcseconds.

**Parallax_Error**

The formal error in the stellar parallax, in milliarcseconds
(mas).

**PM_RA_Error**

The formal error in the proper motion component in the RA
direction expressed in milliarcseconds per Julian year (mas/yr).

**PM_Dec_Error**

The formal error in the proper motion component in the
Decination direction expressed in milliarcseconds per Julian year (mas/yr).

**N_Obs_Hip_Mag**

The number of observations of the Hipparcos magnitude H_p:
this is the number of
photometric observations (or field transits) used for the construction
of the median, standard error, and scatter in H_P

**Quality_Fit**

The goodness-of-fit statistic: this number indicates the
goodness of fit of the astrometric solution.

**Reject_Percent**

The percentage of data that had to be rejected in order
to obtain an acceptable solution.

**Cosmic_Dispersion**

The cosmic dispersion that was added (stochastic
solution).

**Suppl_Cat_Flag**

This flag is set to a non-zero integer if there is an entry
for the star in question in one of the supplemental Hipparcos catalogs.

**Hip_Mag**

The median magnitude H_P of the star in the Hipparcos photometric
system, and defined on the basis of the accepted observations (or field
transits) for a given star.

**Hip_Mag_Error**

The standard error of the median magnitude H_P of the star.

**Scat_Hip_Mag**

The scatter of the H_P observations.

**Var_Data_Annex**

This flag is set to a non-zero integer if there is an entry
for the star in question in the Variability Annex to the Hipparcos Catalog.

**BV_Color**

The (B-V) color index of the star, in, or reduced to, the Johnson
UBV system.

**BV_Color_Error**

The formal error of the (B-V) color index.

**VI_Color**

The Cousins V-I color index of the star.

**UT_Weight_Matrix**

The upper-triangular weight matrix U of the astrometric
solution. U is related to the covariance matrix C by C^{-1} = ~U U, where ~U
represents transposed U. The elements U_i forming the upper triangular matrix
are stored in the order depicted below:

+- -+ | (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) | +- -+on the astrometric parameters RA, Dec, parallax, pm_RA, pm_Dec, and derivatives of proper motions for 7- and 9-parameter solutions.