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 (σα*) 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 (σδ) 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 (σϖ) 0.041 0.029 0.028 0.038 0.057 0.094 0.165 0.317 0.651 2.104 mas
Standard uncertainty in μα* (σμα*) 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 μδ (σμδ) 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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