A classical and a relativistic law of motion for SN1987A
  In this paper we derive some first order differential equations which model
the classical and the relativistic thin layer approximations in the presence of
a circumstellar medium with a density which is decreasing in the distance $z$
from the equatorial plane. The circumstellar medium is assumed to follow a
density profile with $z$ of hyperbolic type, power law type, exponential type
or Gaussian type. The first order differential equations are solved
analytically, or numerically, or by a series expansion, or by Pad\'e
approximants. The initial conditions are chosen in order to model the temporal
evolution of SN 1987A over 23 years. The free parameters of the theory are
found by maximizing the observational reliability which is based on an observed
section of SN 1987A.
