Stellar radial velocity and companion-mass inference
In a Newtonian isolated two-body Keplerian model, the host star's line-of-sight orbital velocity has semi-amplitude K=(2πG/P)^(1/3) Mp sin i/[(Mstar+Mp)^(2/3)√(1−e²)].
Key knowledge
In a Newtonian isolated two-body Keplerian model, the host star's line-of-sight orbital velocity has semi-amplitude K=(2πG/P)^(1/3) Mp sin i/[(Mstar+Mp)^(2/3)√(1−e²)]. The mass function follows by cubing: PK³(1−e²)^(3/2)/(2πG)=Mp³ sin³i/(Mstar+Mp)². Without inclination and stellar-mass constraints this does not give a unique true companion mass. For Mp much smaller than Mstar it commonly constrains Mp sin i.
Values and equations
K=(2πG/P)^(1/3) Mp sin i/[(Mstar+Mp)^(2/3)√(1−e²)]; fM=PK³(1−e²)^(3/2)/(2πG)=Mp³sin³i/(Mstar+Mp)²
- K
- stellar orbital radial-velocity semi-amplitude m s⁻¹
- P
- orbital period s
- G
- gravitational constant m³ kg⁻¹ s⁻²
- Mp,Mstar
- companion and host-star masses kg
- i
- orbital inclination to the sky plane rad
- e
- orbital eccentricity 1
- fM
- single-lined binary mass function kg
Conditions and scope
- P>0,0≤e<1, positive masses; inclination i is the angle between the orbital plane and sky plane, with i=90° edge-on. K is half the maximum-minus-minimum orbital radial velocity, excluding systemic velocity.
- Use sufficiently sampled calibrated velocities and the stated dynamical model. Stellar activity, line-profile changes, instrumental drift and additional companions can alter inference; a Doppler signal alone is not uniquely planetary.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the original chapter's velocity projection, eccentric amplitude and period substitution equations11–14 and activity/line-shape discussion; also read the Archive's explicit retained total-mass/eccentricity convention. Re-expressed the Kepler relation in SI and independently cubed it for the mass function. Excluded dated precision/population claims and interpreting the unknown inclination as a measured mass.
2026-10-10 · Independent AI editorial review: All44 exact root-authored compact records, equations/variable units/conditions and140 origin edges accepted after independently reading final6/18 with bounded primary bodies and matching prior38/122 scientific fingerprints unchanged. Exact claim/edge review is distinct from combined inventory scope and separate CLE26 approval; no entire cited books or old-corpus experimental revalidation is asserted. Receipt: cosmos-completion-independent-content-and-inventory-review.1.
Entry details
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- uni-cosmos-radial-velocity-inference
- Revision
- core.1
- Structured reference record
- University core expansion