Deep Optical Images of the Ejecta Nebula Around the Wolf-Rayet Star WR 8 (HD 62910)

TL;DR

This study presents deep optical imaging of the nebula around Wolf-Rayet star WR 8, revealing complex structures and dust emission features that enhance understanding of its circumstellar environment.

Contribution

It provides detailed optical and infrared imaging of WR 8's nebula, uncovering fine structures and dust distribution not previously observed.

Findings

Nebula spans approximately 6 arcminutes with fine-scale structures.

Infrared data shows a clumpy dust shell coinciding with optical emission.

The star is offset within the dust shell due to its radial dust emission distribution.

Abstract

We report the results of deep H$\alpha$ and [O III] images of the bright WN6/WC4 Wolf-Rayet star WR~8 (HD~62910). These data show considerably more surrounding nebulosity than seen in prior imaging. The brighter portions of the nebula span $\simeq6'$ in diameter and exhibit considerable fine-scale structure including numerous emission clumps and bright head-tail like features presumably due to the effects of the WR star's stellar winds. Due to the overlap of a relatively bright band of unrelated foreground diffuse interstellar H$\alpha$ emission, WR~8's nebula is best viewed via its [O III] emission. A faint $9' \times 13'$ diffuse outer nebulosity is detected surrounding the nebula's main ring of emission. Comparison of the nebula's optical structure with that seen in WISE 22 $\mu$m data shows a similarly clumpy structure but in a better defined emission shell of thermal continuum from dust. The infrared shell is coincident with the nebula's southern [O III] emissions but is mainly seen in the fainter outer portions of the northern [O III] emission clumps. It is this greater radial distance of dust emission in the nebula's northern areas that leads to a striking off-center position of the WR star in the IR shell.