Related papers: A Morphological Diagnostic for Dynamical Evolution…

Galaxies occupy different regions of the [OIII]$\lambda5007$/H$\beta$-versus-[NII]$\lambda6584$/H$\alpha$ emission-line ratio diagram in the distant and local Universe. We investigate the origin of this intriguing result by modelling…

Here we examine 12 Galactic clusters and OB associations containing Wolf-Rayet stars (W-Rs) and/or Luminous Blue Variables (LBVs), in order to assess the progentor masses of these evolved massive stars. We find that in the Milky Way,…

We analyse $\textit{XMM-Newton}$ RGS spectra of Wolf-Rayet (WR) 140, an archetype long-period eccentric WR+O colliding wind binary. We evaluate the spectra of O and Fe emission lines and find that the plasmas emitting these lines have the…

We present follow-up spectroscopy of emission line candidates detected on near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The filters are optimized for the detection of Wolf-Rayet stars and other objects which…

Initial results, techniques, and rationale for a near-infrared survey of evolved emission-line stars toward the Galactic Center are presented. We use images taken through narrow-band emission-line and continuum filters to select candidates…

For three nebulae that have early-WN Wolf-Rayet exciting stars, NGC 6888, WR 8 and Abell 48, we have obtained Herschel-PACS line scans of the [N III] 57 um and [O III] 88 micron lines, along with the 122 and 205 micron lines of [N II]. From…

We present the very first high quality images of the HeII 4686 emission in three high excitation nebulae of the Magellanic Clouds. A fourth high excitation nebula, situated around the WR star BAT99-2, was analysed in a previous letter.…

Wolf-Rayet star's winds can be so dense and so optically thick that the photosphere appears in the highly supersonic part of the outflow, veiling the underlying subsonic part of the star, and leaving the initial acceleration of the wind…

Hypersonic bipolar outflows are a ubiquitous phenomena associated with both young and highly evolved stars. Observations of Planetary Nebulae, the nebulae surrounding Luminous Blue Variables such as $\eta$ Carinae, Wolf Rayet bubbles, the…

We analyze Chandra observations of the Wolf-Rayet (WR) bubble NGC 6888. This WR bubble presents similar spectral and morphological X-ray characteristics to those of S 308, the only other WR bubble also showing X-ray emission. The observed…

We present broad band R and narrow band H_alpha emission line images of a sample of optically selected starburst galaxies from the Markarian lists. The emission line morphology is studied and global properties like luminosities, equivalent…

From stellar evolution models and from observations of Wolf-Rayet stars it is known that massive stars are releasing metal-enriched gas in their Wolf-Rayet phase by means of strong stellar winds. Although HII region spectra serve as…

This paper discusses the location of a sample of planetary nebulae on the HR diagram. We determine the internal velocity fields of 14 planetary nebulae from high-resolution echelle spectroscopy, with the help of photoionization models. The…

Based on time-dependent radiation-hydrodynamics simulations of the evolution of Planetary Nebulae (PNe), we have carried out a systematic parameter study to address the non-trivial question of how the diffuse X-ray emission of PNe with…

Turbulent small-scale structures in the envelopes and winds of massive stars have long been suggested as the cause for excessive line broadening that could not be explained by other mechanisms such as thermal broadening. However, the origin…

During searches for new optical Galactic supernova remnants (SNRs) in the high resolution, high sensitivity Anglo-Australian Observatory/United Kingdom Schmidt Telescope (AAO/UKST) HAlpha survey of the southern Galactic plane, we uncovered…

Are WO-type Wolf Rayet (WR) stars in the final stage of massive star evolution before core-collapse? Although WC- and WO-type WRs have very similar spectra, WOs show a much stronger O VI $\lambda \lambda$3811,34 emission-line feature. This…

Fine-structure mid-infrared emission lines with critical densities in the regime 10^4 to 10^6 cm^-3 can be employed to probe the outflow from Wolf-Rayet stars at radii of \sim 10^15 cm. Narrow-band mid-infrared imaging and spectroscopy of…

Supersonic winds from massive stars carry great amounts of kinetic power and modify the surrounding interstellar medium. Through this interaction a stellar bubble is formed. Theoretical studies and recent observations suggest that the winds…

Wolf-Rayet (WR) stars are the evolved descendants of the most massive stars and show emission-line dominated spectra formed in their powerful stellar winds. Marking the final evolution stage before core collapse, the standard picture of WR…