# 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, ro=None, vo=None)[source]

Class that implements a steady-state spiral potential

$\Phi(R,\phi) = \frac{\mathrm{amp}(t)}{\alpha}\,\cos\left(\alpha\,\ln R - m\,(\phi-\Omega_s\,t-\gamma)\right)$

where

$\mathrm{amp}(t) = \mathrm{amp}\,\times A\,\exp\left(-\frac{[t-t_0]^2}{2\,\sigma^2}\right)$
__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, ro=None, vo=None)[source]

Initialize a transient logarithmic spiral potential localized around to

Parameters:
• amp (float, optional) – Amplitude to be applied to the potential (default: 1).

• omegas (float or Quantity, optional) – Pattern speed (default: 0.65).

• A (float or Quantity, optional) – Amplitude (alpha*potential-amplitude; default: -0.035).

• alpha (float, optional) – Alpha parameter (default: -7.).

• m (int, optional) – Number of arms (default: 2).

• gamma (float or Quantity, optional) – Angle between sun-GC line and the line connecting the peak of the spiral pattern at the Solar radius (in rad; default: 45 degree).

• p (float or Quantity, optional) – Pitch angle.

• sigma (float or Quantity, optional) – “Spiral duration” (sigma in Gaussian amplitude; default: 1.).

• to (float or Quantity, optional) – Time at which the spiral peaks (default: 0.).

Notes

• Either provide:
• alpha

• p

• 2011-03-27 - Started - Bovy (NYU)