Spiral windows for escaping stars

¹ Depto. de Matemática A., University of Alicante, PO Box 99, 03080, Alicante, Spain
² Dépt. de Mathématique, University of Namur, 8 rempart de la Vierge, 5000, Namur, Belgium

Corresponding author: J. Henrard, jacques.henrard@fundp.ac.be

Received: 27 November 2000
Accepted: 23 January 2001

Abstract

The "escape windows"through which stars may escape from a galaxy are investigated by means of Poincaré sections of a simplified axi-symmetric model of the potential. The spiral shape of the windows are analyzed in details by constructing a normal form in the vicinity of an unstable periodic orbit.