On the local birth place of Geminga

¹ Service d'Astrophysique, DSM/DAPNIA, CEA Saclay, Bât. 709, L'Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France e-mail: leonardo.pellizza@cea.fr
² European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching b. München, Germany
³ Université Paris VII Denis-Diderot, 2 place Jussieu, 75251 Paris Cedex 05, France
⁴ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile

Received: 17 November 2004
Accepted: 27 January 2005

Abstract

Using estimates of the distance and proper motion of Geminga and the constraints on its radial velocity posed by the shape of its bow shock, we investigate its birth place by tracing its space motion backwards in time. Our results exclude the λ Ori association as the origin site because of the large distance between both objects at any time. Our simulations place the birth region at approximately 90–240 pc from the Sun, between and in Galactic longitude and and in latitude, most probably inside the Cas-Tau OB association or the Ori OB1a association. We discard the possibility of the progenitor being a massive field star. The association of Geminga with either stellar association implies an upper limit of for the mass of its progenitor. We also propose new members for the Cas-Tau and Ori OB1 associations.