The runaway black hole GRO J1655-40 ^*

¹ Service d'Astrophysique / CEA-Saclay, 91191 Gif-sur-Yvette, France
² Instituto de Astronomía y Física del Espacio/Conicet, Argentina
³ European Southern Observatory, Karl-Schwarzschils-Strasse 2, Garching bei München, 85740, Germany
⁴ Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina
⁵ Instituto de Astronomía, UNAM, Apartado Postal 3-72, 58089 Morelia, Michoacán, México
⁶ Max Planck Institute für Extraterrestrische Physik, Giessenbachstrasse, Postfach 1312, 85748, Garching, Germany
⁷ Max Planck Institute für Plasmaphysik, Boltzmannstrasse 2, 85748, Garching, Germany

Corresponding author: I. F. Mirabel, fmirabel@cea.fr

Received: 15 July 2002
Accepted: 23 September 2002

Abstract

We have used the Hubble Space Telescope to measure the motion in the sky and compute the galactocentric orbit of the black hole X-ray binary GRO J1655-40. The system moves with a runaway space velocity of km s^-1 in a highly eccentric () orbit. The black hole was formed in the disk at a distance greater than 3 kpc from the Galactic centre and must have been shot to such an eccentric orbit by the explosion of the progenitor star. The runaway linear momentum and kinetic energy of this black hole binary are comparable to those of solitary neutron stars and millisecond pulsars. GRO J1655-40 is the first black hole for which there is evidence for a runaway motion imparted by a natal kick in a supernova explosion.