English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We analyze Chandra observations of the Wolf-Rayet (WR) bubble NGC 6888. ThisWR bubble presents similar spectral and morphological X-ray characteristics tothose of S 308, the only other WR bubble also showing X-ray emission. Theobserved spectrum is soft, peaking at the N VII line emission at 0.5 keV withadditional line emission at 0.7 - 0.9 keV and a weak tail of harder emission upto ~1.5 keV. This spectrum can be described by a two-temperature optically thinplasma emission model (T_{1}~1.4x10^{6} K, T_{2}~7.4x10^{6} K). We confirm theresults of previous X-ray observations that no noticeable temperaturevariations are detected in the nebula. The X-ray-emitting plasma is distributedin three apparent morphological components: two caps along the tips of themajor axis and an extra contribution toward the northwest blowout not reportedin previous analysis of the X-ray emission toward this WR nebula. Using theplasma model fits of the Chandra ACIS spectra for the physical properties ofthe hot gas and the ROSAT PSPC image to account for the incomplete coverage ofChandra observations, we estimate a luminosity of L_X = (7.7\pm0.1)x10^{33}erg/s for NGC 6888 at a distance of 1.26 kpc. The average rms electron densityof the X-ray-emitting gas is >= 0.4 cm^{-3} for a total mass >= 1.2 Msun.

X-ray Emission from the Wolf-Rayet Bubble NGC 6888. I. Chandra ACIS-S Observations