2009MNRAS.394.1440M

Using new and archival radio data, we have measured the proper motion of the black hole X-ray binary V404 Cyg to be 9.2±0.3mas/yr. Combined with the systemic radial velocity from the literature, we derive the full three-dimensional heliocentric space velocity of the system, which we use to calculate a peculiar velocity in the range 47-102km/s, with a best-fitting value of 64km/s. We consider possible explanations for the observed peculiar velocity and find that the black hole cannot have formed via direct collapse. A natal supernova is required, in which either significant mass (∼11M_☉) was lost, giving rise to a symmetric Blaauw kick of up to ∼65km/s, or, more probably, asymmetries in the supernova led to an additional kick out of the orbital plane of the binary system. In the case of a purely symmetric kick, the black hole must have been formed with a mass ∼9M_☉, since when it has accreted 0.5-1.5M_☉ from its companion.