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Table 1.
Constraints that need to be satisfied in order for a GDR2 object to be selected as a lens star.
| GDR2 column name | Relation | Value | Unit | Description |
|---|---|---|---|---|
| DUPLICATED_SOURCE | = | FALSE | – | Reject duplicated objects that are likely to have astrometric and photometric problems. |
| FRAME_ROTATOR_OBJECT_TYPE | = | 0 | – | Reject known extra-galactic objects. |
| ASTROMETRIC_PARAMS_SOLVED | = | 31 | – | Only accept objects that have a 5-parameter astrometric solution. |
| ϖ/σ[ϖ] | > | 4 | – | Only accept objects with a sufficiently precise parallax measurement. |
| ϖ | > | 0 | mas | Reject objects with a non-positive parallax. |
| ϖ | < | 769 | mas | Reject objects with a parallax greater than that of Proxima Centauri, which has a Gaia parallax of 768.529±0.254 mas. |
|
< | 1.2 max{1,exp[0.2 (19.5−G)]} | – | Reject objects with a spurious astrometric solution. |
| ASTROMETRIC_EXCESS_NOISE_SIG | < | 3 | – | Reject objects with significant excess noise in the astrometric solution. |
Notes. The symbols ϖ and σ[ϖ] represent the corrected parallax and its inflated uncertainty, respectively. Furthermore, χ2 = ASTROMETRIC_CHI2_AL and ν = ASTROMETRIC_N_GOOD_OBS_AL − 5.
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