The origin of the runaway high-mass X-ray binary HD 153919/4U1700-37

Abstract

Based on its Hipparcos proper motion, we propose that the high-mass X-ray binary HD 153919/4U1700-37 originates in the OB association Sco OB1. At a distance of 1.9 kpc the space velocity of 4U1700-37 with respect to Sco OB1 is 75 km s-1. This runaway velocity indicates that the progenitor of the compact X-ray source lost about 7 during the (assumed symmetric) supernova explosion. The system's kinematical age is about million years which marks the date of the supernova explosion forming the compact object. The present age of Sco OB1 is 8 Myr; its suggested core, NGC 6231, seems to be somewhat younger (~5 Myr). If HD 153919/4U1700-37 was born as a member of Sco OB1, this implies that the initially most massive star in the system terminated its evolution within 6 million years, corresponding to an initial mass 30 . With these parameters the evolution of the binary system can be constrained.