Chandra imaging and spectroscopy of the eastern XA region of the cygnus loop supernova remnant

R. L. McEntaffer, T. Brantseg

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The XA region of the Cygnus Loop is a bright knot of X-ray emission on the eastern edge of the supernova remnant. The emission results from the interaction of the supernova blast wave with density enhancements at the edge of a precursor formed cavity. However, this interaction is complex given the irregular morphology of the cavity wall. To study the nature and origin of the X-ray emission, we use high spatial resolution images from Chandra. We extract spectra from these images to analyze the physical conditions of the plasma. Our goal is to probe the density of various regions to form a picture of the cavity wall and characterize the interaction between this supernova and the local interstellar medium. We find that a series of regions along the edge of the X-ray emission appears to trace out the location of the cavity wall. The best-fit plasma models result in two temperature component equilibrium models for each region. The low-temperature components have densities that are an order of magnitude higher than the high-temperature components. The high-density plasma may exist in the cavity wall where it equilibrates rapidly and cools efficiently. The low-density plasma is interior to the enhancement and heated further by a reverse shock from the wall. Calculations of shock velocities and timescales since shock heating are consistent with this interpretation. Furthermore, we find a bright knot of emission indicative of a discrete interaction of the blast wave with a high-density cloud in the cavity wall with a size scale 0.1pc. Aside from this, other extractions made interior to the X-ray edge are confused by line-of-sight projection of various components. Some of these regions show evidence of detecting the cavity wall but their location makes the interpretation difficult. In general, the softer plasmas are well fit at temperatures 〈kT〉 0.11keV, with harder plasmas at temperatures of 〈kT〉 0.27keV. All regions displayed consistent metal depletions most notably in N, O, and Ne at an average of 0.54, 0.55, and 0.36 times solar, respectively.

Original languageEnglish (US)
Article number99
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 1 2011

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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