Table 1
Model parameters used by BASE.
| Widest | Data types b | |||||||||
|
|
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| Symbol | Designation | Unit | Prior Support | Cyclic a | Prior type | AM | RV | AM+RV | ||
|
|
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| e | eccentricity | 1 | [0, 1) | uniform | × | × | × | |||
| f | orbital frequency | d-1 | (0, 1] | Jeffreys | × | × | × | |||
| χ | mean anomaly at t1 over 2π | 1 | [0, 1) | × | uniform | × | × | × | ||
| ω, ω 2 | argument of periapsis c | rad | [0, 2π) | × | uniform | × | × | × | ||
| i | inclination | rad | [0, π) | uniform | × | × | ||||
| Ω | position angle of the ascending nodee | rad | [0, 2π) | × | uniform | × | × | |||
|
semi-major axis of orbit of secondary around primary over distance | mas | [10-3, 10-5] f | Jeffreys | × | |||||
| ϖ | parallax | arcsec | (0, 0.77] g | Jeffreys | × | |||||
| V | RV offset | ms-1 | — | uniform | × | × | ||||
| K, K i | RV semi-amplitude d | ms-1 | ≥0 | mod. Jeffreys | × | × | ||||
| τ + | standard deviation of additional AM noise | mas | ≥0 | mod. Jeffreys | × | × | ||||
| σ + | standard deviation of additional RV noise | ms-1 | ≥0 | mod. Jeffreys | × | × | ||||
Notes.
For cyclic parameters θ, the indicated lower and upper bounds are treated as equivalent by BASE (see Sect. 2.3).
The types of data for which each parameter is relevant. Abbreviations: AM (astrometry), RV (radial velocities).
The widest prior range of Ω reduces to [0,π) if no RV data are provided, in which case it cannot be determined whether a given node is ascending or descending; then, Ω is defined to be the position angle of the first node.
Lower bound corresponds to AM measurement uncertainty of 1 μas; upper bound according to wide-binary observations by Tolbert (1964).
Interval includes trigonometric parallax of the nearest star, Proxima Centauri (Perryman et al. 1997).
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