HST STIS Observations of the Mixing Layer in the Cat’s Eye Nebula
Abstract
Planetary nebulae (PNe) are expected to have a ∼105 K interface layer between the ≥slant 106 K inner hot bubble and the ∼104 K optical nebular shell. The PN structure and evolution, and the X-ray emission, depend critically on the efficiency of the mixing of material at this interface layer. However, neither its location nor its spatial extent have ever been determined. Using high-spatial resolution HST STIS spectroscopic observations of the N v λ λ 1239,1243 lines in the Cat’s Eye Nebula (NGC 6543), we have detected this interface layer and determined its location, extent, and physical properties for the first time in a PN. We confirm that this interface layer, as revealed by the spatial distribution of the N v λ1239 line emission, is located between the hot bubble and the optical nebular shell. We estimate a thickness of 1.5× {10}16 cm and an electron density of ∼200 cm-3 for the mixing layer. With a thermal pressure of ∼2 × 10-8 dyn cm-2, the mixing layer is in pressure equilibrium with the hot bubble and ionized nebular rim of NGC 6543.
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The observations are associated with program #12509.- Publication:
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The Astrophysical Journal
- Pub Date:
- May 2016
- DOI:
- 10.3847/2041-8205/822/1/L19
- arXiv:
- arXiv:1603.06689
- Bibcode:
- 2016ApJ...822L..19F
- Keywords:
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- planetary nebulae: general;
- planetary nebulae: individual: NGC 6543;
- stars: winds;
- outflows;
- X-rays: ISM;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in the ApJ Letters