The origin of the high-mass X-ray binary 4U 2206+54/BD+532790

Abstract

Based on the Gaia EDR3 astrometric parameters and our new systemic radial velocity of the high-mass X-ray binary 4U 2206+54/BD+532790, 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+532820 (B0V; ${\cal L}$~10^4.7${\cal L}$_⊙). 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^-1 with respect to this member star (BD+532820) of the Cep OB1 association. This runaway velocity indicates that the progenitor of the neutron star hosted by 4U 2206+54 lost about 4-9 M_⊙ during the supernova explosion and the latter one received a kick velocity of at least 200-350 km s^-1 . Since the high-mass X-ray binary 4U 2206+54/BD+532790 was born as a member of a subgroup of Cep OB1, the initially most massive star in the system terminated its evolution within $\lesssim 7-9$ Myr, corresponding to an initial mass $\gtrsim 32$ M_⊙.