Transient logarithmic spiral potential

class galpy.potential.TransientLogSpiralPotential(amp=1.0, omegas=0.65, A=-0.035, alpha=-7.0, m=2, gamma=0.7853981633974483, p=None, sigma=1.0, to=0.0)

Class that implements a steady-state spiral potential

V(r,phi,t) = A(t)/alpha cos(alpha ln(r) - m(phi - Omegas*t-gamma))

where

A(t) = A_max exp(- [t-to]^2/sigma^2/2.)

__init__(amp=1.0, omegas=0.65, A=-0.035, alpha=-7.0, m=2, gamma=0.7853981633974483, p=None, sigma=1.0, to=0.0)

NAME:

__init__

PURPOSE:

initialize a transient logarithmic spiral potential localized around to

INPUT:

amp - amplitude to be applied to the potential (default: 1., A below)

gamma - angle between sun-GC line and the line connecting the peak of the spiral pattern at the Solar radius (in rad; default=45 degree)

A - force amplitude (alpha*potential-amplitude; default=0.035)

omegas= - pattern speed (default=0.65)

m= number of arms

to= time at which the spiral peaks

sigma= “spiral duration” (sigma in Gaussian amplitude)

Either provide:

1. alpha=
2. p= pitch angle (rad)

OUTPUT:

(none)

HISTORY:

2011-03-27 - Started - Bovy (NYU)