BD+43 3654 -- a blue straggler?

TL;DR

This paper proposes that the runaway star BD+43 3654 is a blue straggler formed through binary interactions in Cyg OB2, explaining its youth and suggesting a mechanism for high-velocity star ejections.

Contribution

It introduces the hypothesis that BD+43 3654 is a blue straggler formed via binary encounters, and links this process to the ejection of high-velocity stellar remnants.

Findings

BD+43 3654 likely originated from binary interactions in Cyg OB2.

The star's youth is explained as a blue straggler formation.

Binary encounters may produce high-velocity stellar remnants.

Abstract

The astrometric data on the runaway star BD+43 3654 are consistent with the origin of this O4If star in the center of the Cyg OB2 association, while BD+43 3654 is younger than the association. To reconcile this discrepancy, we suggest that BD+43 3654 is a blue straggler formed via a close encounter between two tight massive binaries in the core of Cyg OB2. A possible implication of this suggestion is that the very massive (and therefore apparently very young) stars in Cyg OB2 could be blue stragglers as well. We also suggest that the binary-binary encounter producing BD+43 3654 might be responsible for ejection of two high-velocity stars (the stripped helium cores of massive stars) -- the progenitors of the pulsars B2020+28 and B2021+51.