The inner planet was announced by Butler et
al. in January 1997.
Analysis of extended velocity measurements
reveals additional velocity variations.
Two-Planet Fit:
A Two-Keplerian model (solid line) is fit to the measured velocities.
Here the velocity wobble caused by the outer planet has been
removed for clarity,
leaving the wobble caused by the inner planet.
These residual velocities (dots) are phased at the 14.65-d period
of the inner planet, showing the significant reduction in the
residuals compared with the one-planet model. By including a
second planet in the model, the RMS of the residuals dropped
from 39.5 m/s to 11.6 m/s.
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One-Planet Fit:
Velocities for 55 Cancri, phased at the best-fit period of 14.65 d.
The dashed line represents the best-fit (single-planet) keplerian.
The RMS of 38 m/s is well above the typical velocity
errors of 3-10 m/s, showing the inadequacy of a single-planet model.
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| Note: Assumes Mstar=0.95.
The outer planet is 0.5 arcsec
from the star, making it the best extrasolar planet
for direct imaging by a coronograph. |