Gaia Data Release 2 - The astrometric solution

L. Lindegren; J. Hernández; A. Bombrun; S. Klioner; U. Bastian; M. Ramos-Lerate; A. de Torres; H. Steidelmüller; C. Stephenson; D. Hobbs; U. Lammers; M. Biermann; R. Geyer; T. Hilger; D. Michalik; U. Stampa; P.J. McMillan; J. Castañeda; M. Clotet; G. Comoretto; M. Davidson; C. Fabricius; G. Gracia; N.C. Hambly; A. Hutton; A. Mora; J. Portell; F. van Leeuwen; U. Abbas; A. Abreu; M. Altmann; A. Andrei; E. Anglada; L. Balaguer-Núñez; C. Barache; U. Becciani; S. Bertone; L. Bianchi; S. Bouquillon; G. Bourda; T. Brüsemeister; B. Bucciarelli; D. Busonero; R. Buzzi; R. Cancelliere; T. Carlucci; P. Charlot; N. Cheek; M. Crosta; C. Crowley; J. de Bruijne; F. de Felice; R. Drimmel; P. Esquej; A. Fienga; E. Fraile; M. Gai; N. Garralda; J.J. González-Vidal; R. Guerra; M. Hauser; W. Hofmann; B. Holl; S. Jordan; M.G. Lattanzi; H. Lenhardt; S. Liao; E. Licata; T. Lister; W. Löffler; J. Marchant; J.-M. Martin-Fleitas; R. Messineo; F. Mignard; R. Morbidelli; E. Poggio; A. Riva; N. Rowell; E. Salguero; M. Sarasso; E. Sciacca; H. Siddiqui; R.L. Smart; A. Spagna; I. Steele; F. Taris; J. Torra; A. van Elteren; W. van Reeven; A. Vecchiato

doi:10.1051/0004-6361/201832727

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Volume 616 (August 2018)

A&A, 616 (2018) A2

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Gaia Data Release 2

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Table B.1

Summary statistics for the 1332 million sources in Gaia DR2 with a full astrometric solution (five astrometric parameters).

	Median value at magnitude G

Quantity	≤ 12	13	14	15	16	17	18	19	20	21	Unit
Fraction of sources with 5-param. solution	99.1	99.0	99.0	99.0	98.9	98.6	97.6	94.5	82.9	15.9	%
Standard uncertainty in α (σ_α*) at J2015.5	0.033	0.023	0.023	0.031	0.047	0.077	0.137	0.268	0.548	1.457	mas
Standard uncertainty in δ (σ_δ) at J2015.5	0.030	0.022	0.020	0.027	0.041	0.069	0.123	0.242	0.490	1.559	mas
Standard uncertainty in ϖ (σ_ϖ)	0.041	0.029	0.028	0.038	0.057	0.094	0.165	0.317	0.651	2.104	mas
Standard uncertainty in μ_α* (σ_μα*)	0.068	0.047	0.047	0.063	0.096	0.158	0.280	0.550	1.164	3.114	mas yr⁻¹
Standard uncertainty in μ_δ (σ_μδ)	0.059	0.042	0.040	0.054	0.082	0.137	0.243	0.479	1.011	3.374	mas yr⁻¹
Fraction with significant excess noise	20.6	21.0	17.8	17.9	18.4	19.2	20.6	21.2	18.2	10.6	%
Excess source noise (when significant)	0.183	0.249	0.311	0.331	0.367	0.474	0.701	1.226	2.235	4.563	mas
Number of visibility periods used	13	13	13	13	13	12	12	12	12	9
Number of field-of-view transits used	26	26	26	26	25	25	24	23	22	12
Number of good CCD observations AL	220	227	226	223	218	215	212	199	194	102
Fraction of bad CCD observations AL	2.7	0.8	0.0	0.4	0.4	0.4	0.4	0.5	0.4	0.5	%

Notes. The table gives the median quantities at the magnitudes indicated in the header. For G ≤ 12 the median values were computed using all the sources in that range; at other magnitudes about 2 million sources were used around the indicated G.

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