Ultraluminous X-ray Sources: Beambags and Optical Counterparts

TL;DR

This paper reviews optical observations of ionized nebulae around ultraluminous X-ray sources (ULXs), arguing for ULX-driven bubbles over traditional models, and reports new ULX discoveries and a microquasar analog.

Contribution

It introduces new evidence supporting ULX-wind/jet driven bubbles and reports the discovery of ULXs in large SNR candidates and a microquasar-like system.

Findings

Evidence against superbubble and hypernova remnant models

Discovery of ULXs in large SNR candidates

Identification of a microquasar analog in NGC 7793

Abstract

A significant fraction of ultraluminous X-ray sources appear to be embedded in observable ionized nebulae that take the form of large, several 100 pc diameter interstellar bubbles. Here we review optical observations of these bubbles, their importance for our understanding of the nature of ULXs, the energetics involved and their formation and evolution. Among the results obtained are new arguments against conventional superbubble scenarios and hypernova remnants, and we present the case in favour of ULX-wind/jet driven bubbles. We report the discovery of new ULXs in very large SNR candidates in nearby galaxies, and finally present an image of a triple X-ray source coincident with the radio-bright bubble S26 in the galaxy NGC 7793 which appears to be a clone of the microquasar SS433/W50 system.