NAME:
vR
PURPOSE:
return radial velocity at time t
vo= (Object-wide default) physical scale for velocities to use to convert
use_physical= use to override Object-wide default for using a physical scale for output
INPUT:
t - (optional) time at which to get the radial velocity
OUTPUT:
vR(t)
HISTORY:
2010-09-21 - Written - Bovy (NYU)