On the origin of runaway binaries: the case of the HMXB 4U 2206+54/BD +53 2790

Abstract

We present most probable place and time of the origin of the runaway high-mass X-ray binary 4U 2206+54 based on its Gaia EDR3 astrometric parameters and our new systemic radial velocity. We studied the trace back motion of the system and propose that it originated in the subgroup of the Cepheus OB1 association (Age∼4-10 Myr) with its brightest star BD+53 2820 (B0V; L∼104.7L⊙). The kinematic age of 4U 2206+54 is about 2.8 ± 0.4 Myr, it is at a distance of 3.1-3.3 kpc and has a space velocity of 75-100 km/s with respect to this member star (BD+53 2820) of the Cep OB1 association. This runaway velocity indicates that the progenitor of the neutron star hosted by 4U 2206+54 lost about 4-9M⊙ during the supernova explosion and the latter one received a kick velocity of at least 200-350 km/s. The high-mass X-ray binary 4U 2206+54/BD+53 2790 was born as a member of a subgroup of the Cep OB1 association, the initially most massive star in the system terminated its evolution within ≲ 7 − 9 Myr, corresponding to an initial mass ≳ 32 M⊙.