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Table 1

Model parameters used by BASE.

Widest Data types b

Symbol Designation Unit Prior Support Cyclic a Prior type AM RV AM+RV

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. 

(a)

For cyclic parameters θ, the indicated lower and upper bounds are treated as equivalent by BASE (see Sect. 2.3).

(b)

The types of data for which each parameter is relevant. Abbreviations: AM (astrometry), RV (radial velocities).

(c)

Normal mode employs ω, while binary mode employs ω2.

(d)

Normal mode employs K, while binary mode employs K1 and K2.

(e)

The widest prior range of Ω reduces to [0) 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.

(f)

Lower bound corresponds to AM measurement uncertainty of 1 μas; upper bound according to wide-binary observations by Tolbert (1964).

(g)

Interval includes trigonometric parallax of the nearest star, Proxima Centauri (Perryman et al. 1997).

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