Attractive branch of the Kepler–isochrone transformation
= Attractive branch of the Kepler–isochrone transformation
For bound old <Kepler orbits>, $E<0$, $\lambda<0$ and $\bar E>0$ give a positive radius, positive isochrone scale $b$, and positive transformed <mass>. The shifted <energy> is $\bar E-k=\bar E/\lambda<0$. For unbound old orbits with $E>0$, $1/2<\lambda\leq1$ gives an attractive unbound isochrone branch. The case $\lambda=0$ is handled by the separate <Kepler–harmonic radial duality>.