Population I Wolf-Rayet Runaway Stars: the Case of WR124 and its Expanding Nebula M1-67

TL;DR

This study uses Hubble Space Telescope imaging to determine the distance and runaway status of Wolf-Rayet star WR124 and its nebula M1-67, highlighting implications for supernovae and gamma-ray bursts in low-metallicity galaxies.

Contribution

It provides a geometric distance measurement to WR124 and confirms its runaway nature, offering insights into supernova and gamma-ray burst environments.

Findings

Distance to WR124 is 3.35 +/- 0.67 kpc.

WR124 is confirmed as an extreme runaway star.

Implications for supernovae and gamma-ray bursts in low-metallicity galaxies.

Abstract

In 1997 and 2008 we used the WFPC2 camera on board of the Hubble Space Telescope to obtain two sets of narrow-band H$\alpha$ images of the runaway Wolf-Rayet (WR) star WR 124 surrounded by its nebula M1-67. This two-epoch imaging provides an expansion parallax and thus a practically assumption-free geometric distance to the nebula, d=3.35 +/- 0.67 kpc. Combined with the global velocity distribution in the ejected nebula, this confirms the extreme runaway status of WR 124. WR stars embedded within such ejection nebulae, at the point of core-collapse would produce different supernova characteristics from those expected for stars surrounded by wind-filled cavities. In galaxies with extremely low ambient metallicity, Z <= 10^{-3} Z_Sun, gamma-ray bursts originating from fast-moving runaway WR stars may produce afterglows which appear to be coming from regions with a relatively homogeneous circumburst medium.