# galpy.df.impulse_deltav_plummer¶

galpy.df.impulse_deltav_plummer(v, y, b, w, GM, rs)[source]

NAME:

impulse_deltav_plummer

PURPOSE:

calculate the delta velocity to due an encounter with a Plummer sphere in the impulse approximation; allows for arbitrary velocity vectors, but y is input as the position along the stream

INPUT:

v - velocity of the stream (nstar,3)

y - position along the stream (nstar)

b - impact parameter

w - velocity of the Plummer sphere (3)

GM - mass of the Plummer sphere (in natural units)

rs - size of the Plummer sphere

OUTPUT:

deltav (nstar,3)

HISTORY:

2015-04-30 - Written based on Erkal’s expressions - Bovy (IAS)