Runaway Stars as Possible Sources of the Elliptical Ring Structures in NGC 7538

Abstract

Two large, ∼500 M_⊙ elliptical ring structures have been identified in the high-mass star-forming region NGC 7538. The origin of these ring structures is unknown, so we investigate the possibility that a runaway O- or B-type star may have originated in or passed through the region and created either or both of the ring structures via stellar wind. In testing this hypothesis, we identify one candidate star, BD +61 2408, that may have formed the northern ring. It is a B3e star with a mass of ∼8 M_⊙ and a surface temperature of ∼20,000 K. Its position, motion, timescale, and spectral type are all consistent with the star being a candidate for having formed one of the ring structures in NGC 7538.