Publications by Patrick Roche
Monthly Notices of the Royal Astronomical Society 359 (2005) 1386-1392
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 P ← P , obtained with Phoenix on Gemini South at resolving powers of up to 75000, resolve the line into five hyperfine components separated by 20-60 km s as a result of the coupling of the I = 5/2 nuclear spin of Al with the total electronic angular momentum J. The isotope Al has a different nuclear spin of I = 5, and a different HFS, which allows us to place a 3σ upper limit on the Al/ AI 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. © 2005 RAS.
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