Hyperfine splitting of [Al vi] 3.66 μm and the Al isotopic ratio in NGC 6302 |
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| Authors: | S Casassus P J Storey M J Barlow P F Roche |
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| Institution: | Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile;Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT;Denys Wilkinson Building, Physics Department, Oxford University, Keble Road, Oxford OX1 3RH |
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| Abstract: | The core of planetary nebula NGC 6302 is filled with high-excitation photoionized gas at low expansion velocities. It represents a unique astrophysical situation in which to search for hyperfine structure (HFS) in coronal emission lines from highly ionized species. HFS is otherwise blended by thermal or velocity broadening. Spectra containing Al vi ] 3.66 μm 3P2←3P1 , obtained with Phoenix on Gemini South at resolving powers of up to 75 000, resolve the line into five hyperfine components separated by 20–60 km s?1 as a result of the coupling of the I = 5/2 nuclear spin of 27Al with the total electronic angular momentum J . The isotope 26Al has a different nuclear spin of I = 5 , and a different HFS, which allows us to place a 3σ upper limit on the 26Al/27Al abundance ratio of 1/33. We measure the HFS magnetic dipole coupling constants for Al vi ], and provide the first estimates of the electric quadrupole HFS coupling constants obtained through astronomical observations of an atomic transition. |
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| Keywords: | atomic data atomic processes line: identification line: profiles ISM: abundances planetary nebulae: individual: NGC 6302 |
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