TGas Source (gaiadr1.tgas_source)

The table has 2057050 rows, 60 columns.

Description

This table is a subset of GaiaSource comprising those stars in the Hipparcos and Tycho-2 Catalogues for which a full 5-parameter astrometric solution has been possible in Gaia Data Release 1. This is possible because the early Hipparcos epoch positions break some degeneracies due to the limited Gaia time coverage. The table contains a substantial fraction of the around 2.5 million stars in the Hipparcos and Tycho-2 catalogue. Many stars have been excluded due to several reasons, such as saturation, cross-match errors or bad astrometric solution.

Attribution

If you have used Gaia data in your research, please use the following acknowledgement:

This work has made use of data from the European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

More information can be found on the credit and citation instructions page.

Columns

Name Type UCD Unit Description
hip int meta.id.cross

Hipparcos identifier
tycho2_id char meta.id.cross

Tycho 2 identifier
solution_id long meta.id
meta.version

Solution Identifier
source_id long meta.id
meta.main
meta.ref

Unique source identifier
random_index long meta.code

Random index used to select subsets
ref_epoch double meta.ref
time.epoch 		Time[Julian Years]

Reference epoch
ra double pos.eq.ra
meta.main 		Angle[deg]

Right ascension
ra_error double stat.error
pos.eq.ra 		Angle[mas]

Standard error of right ascension
dec double pos.eq.dec
meta.main 		Angle[deg]

Declination
dec_error double stat.error
pos.eq.dec 		Angle[mas]

Standard error of declination
parallax double pos.parallax Angle[mas]

Parallax
parallax_error double stat.error
pos.parallax 		Angle[mas]

Standard error of parallax
pmra double pos.pm
pos.eq.ra 		Angular Velocity[mas/year]

Proper motion in right ascension direction
pmra_error double stat.error
pos.pm
pos.eq.ra 		Angular Velocity[mas/year]

Standard error of proper motion in right ascension direction
pmdec double pos.pm
pos.eq.dec 		Angular Velocity[mas/year]

Proper motion in declination direction
pmdec_error double stat.error
pos.pm
pos.eq.dec 		Angular Velocity[mas/year]

Standard error of proper motion in declination direction
ra_dec_corr float stat.correlation

Correlation between right ascension and declination
ra_parallax_corr float stat.correlation

Correlation between right ascension and parallax
ra_pmra_corr float stat.correlation

Correlation between right ascension and proper motion in right ascension
ra_pmdec_corr float stat.correlation

Correlation between right ascension and proper motion in declination
dec_parallax_corr float stat.correlation

Correlation between declination and parallax
dec_pmra_corr float stat.correlation

Correlation between declination and proper motion in right ascension
dec_pmdec_corr float stat.correlation

Correlation between declination and proper motion in declination
parallax_pmra_corr float stat.correlation

Correlation between parallax and proper motion in right ascension
parallax_pmdec_corr float stat.correlation

Correlation between parallax and proper motion in declination
pmra_pmdec_corr float stat.correlation

Correlation between proper motion in right ascension and proper motion in declination
astrometric_n_obs_al int meta.number

Total number of observations AL
astrometric_n_obs_ac int meta.number

Total number of observations AC
astrometric_n_good_obs_al int meta.number

Number of good observations AL
astrometric_n_good_obs_ac int meta.number

Number of good observations AC
astrometric_n_bad_obs_ac int meta.number

Number of bad observations AC
astrometric_n_bad_obs_al int meta.number

Number of bad observations AL
astrometric_delta_q float stat.value

Hipparcos/Gaia data discrepancy (Hipparcos subset of TGAS only)
astrometric_excess_noise double stat.value Angle[mas]

Excess noise of the source
astrometric_excess_noise_sig double stat.value

Significance of excess noise
astrometric_primary_flag boolean meta.code

Primary or seconday
astrometric_relegation_factor float arith.factor

Relegation factor
astrometric_weight_al float stat.weight
stat.mean 		Angle[mas^-2]

Mean astrometric weight of the source
astrometric_weight_ac float stat.weight
stat.mean 		Angle[mas^-2]

Mean astrometric weight of the source
astrometric_priors_used int

Type of prior used in the astrometric solution
matched_observations short meta.number

Amount of observations matched to this source
duplicated_source boolean

Source with duplicate sources
scan_direction_strength_k1 float

Degree of concentration of scan directions across the source
scan_direction_strength_k2 float

Degree of concentration of scan directions across the source
scan_direction_strength_k3 float

Degree of concentration of scan directions across the source
scan_direction_strength_k4 float

Degree of concentration of scan directions across the source
scan_direction_mean_k1 float Angle[deg]

Mean position angle of scan directions across the source
scan_direction_mean_k2 float Angle[deg]

Mean position angle of scan directions across the source
scan_direction_mean_k3 float Angle[deg]

Mean position angle of scan directions across the source
scan_direction_mean_k4 float Angle[deg]

Mean position angle of scan directions across the source
phot_g_n_obs int meta.number

Number of observations contributing to G photometry
phot_g_mean_flux double phot.flux
stat.mean
em.opt 		Flux[e-/s]

G-band mean flux
phot_g_mean_flux_error double stat.error
phot.flux
stat.mean
em.opt 		Flux[e-/s]

Error on G-band mean flux
phot_g_mean_mag double phot.mag
stat.mean
em.opt 		Magnitude[mag]

G-band mean magnitude
phot_variable_flag char meta.code
src.var

Photometric variability flag
l double pos.galactic.lon Angle[deg]

Galactic longitude
b double
ecl_lon double
ecl_lat double
pos char

Spherical point computed from right ascension and declination