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Title: X-ray emission from the Wolf-Rayet bubble NGC 6888. I. Chandra ACIS-S observations

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 {sub 1} ∼ 1.4 × 10{sup 6} K, T {sub 2} ∼ 7.4 × 10{sup 6} 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 L {sub X} = (7.7 ±more » 0.1) ×10{sup 33} erg s{sup –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{sup –3} for a total mass ≳ 1.2 M {sub ☉}.« less
Authors:
;  [1] ; ;  [2]
  1. Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada (Spain)
  2. Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)
Publication Date:
OSTI Identifier:
22340024
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 147; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLOWOUTS; COSMIC X-RAY SOURCES; DISTANCE; ELECTRON DENSITY; EMISSION; IMAGES; KEV RANGE; LUMINOSITY; MASS; NEBULAE; OPTICALLY THIN PLASMA; SPECTRA; STARS; WOLF-RAYET STARS; X RADIATION