X-ray emission from the wolf-rayet bubble NGC 6888. I. Chandra ACIS-S observations

J. A. Toalá, M. A. Guerrero, R. A. Gruendl, Y. H. Chu

Research output: Contribution to journalArticlepeer-review

Abstract

We analyze Chandra observations of the Wolf-Rayet (W-R) bubble NGC 6888. This W-R bubble presents similar spectral and morphological X-ray characteristics to those of S 308, the only other W-R bubble also showing X-ray emission. The observed spectrum is soft, peaking at the N VII line emission at 0.5 keV, with additional line emission at 0.7-0.9 keV and a weak tail of harder emission up to 1.5 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T 11.4 × 106 K, T27.4 × 106 K). We confirm the results of previous X-ray observations that no noticeable temperature variations are detected in the nebula. The X-ray-emitting plasma is distributed in three apparent morphological components: two caps along the tips of the major axis and an extra contribution toward the northwest blowout not reported in previous analyses of the X-ray emission toward this W-R nebula. Using the plasma model fits of the Chandra ACIS spectra for the physical properties of the hot gas and the ROSAT PSPC image to account for the incomplete coverage of Chandra observations, we estimate a luminosity of LX = (7.7 ± 0.1) ×1033 erg s-1 for NGC 6888 at a distance of 1.26 kpc. The average rms electron density of the X-ray-emitting gas is ≳ 0.4 cm-3 for a total mass ≳ 1.2 M.

Original languageEnglish (US)
Article number30
JournalAstronomical Journal
Volume147
Issue number2
DOIs
StatePublished - Feb 2014

Keywords

  • ISM: bubbles
  • ISM: individual objects (NGC 6888)
  • X-rays: individual (NGC 6888)
  • stars: Wolf-Rayet
  • stars: winds outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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