Discovery of Twin Wolf-Rayet Stars Powering Double Ring Nebulae

TL;DR

This study reports the discovery of twin Wolf-Rayet stars with surrounding nebulae, revealing complex interactions of stellar winds and dust in a newly identified stellar association 4.9 kpc away.

Contribution

First spectroscopic identification of twin Wolf-Rayet stars with associated nebulae, highlighting a complex stellar environment and potential early-stage nebula collision.

Findings

Twin Wolf-Rayet stars surrounded by infrared-bright nebulae

Nebulae likely formed from stellar ejecta during earlier evolutionary phases

Stars are part of a new stellar association near the Galaxy's Long Bar

Abstract

We have spectroscopically discovered a pair of twin, nitrogen-type, hydrogen-rich, Wolf-Rayet stars (WN8-9h) that are both surrounded by circular, mid-infrared-bright nebulae detected with the Spitzer Space Telescope and MIPS instrument. The emission is probably dominated by a thermal continuum from cool dust, but also may contain contributions from atomic line emission. There is no counterpart at shorter Spitzer/IRAC wavelengths, indicating a lack of emission from warm dust. The two nebulae are probably wind-swept stellar ejecta released by the central stars during a prior evolutionary phase. The nebulae partially overlap on the sky and we speculate on the possibility that they are in the early stage of a collision. Two other evolved massive stars have also been identified within the area subtended by the nebulae, including a carbon-type Wolf-Rayet star (WC8) and an O7-8 III-I star, the latter of which appears to be embedded in one of the larger WN8-9h nebulae. The derived distances to these stars imply that they are coeval members of an association lying 4.9 (1.2) kpc from Earth, near the intersection of the Galaxy's Long Bar and the Scutum-Centaurus spiral arm. This new association represents an unprecedented display of complex interactions between multiple stellar winds, outflows, and the radiation fields of evolved massive stars.