# galpy.df.impulse_deltav_hernquist¶

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

NAME:

impulse_deltav_hernquist

PURPOSE:

calculate the delta velocity to due an encounter with a Hernquist 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 Hernquist sphere (3)

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

rs - size of the Hernquist sphere

OUTPUT:

deltav (nstar,3)

HISTORY:

2015-08-13 SANDERS, using Wyn Evans calculation