Opacity in the upper atmosphere of AU Mic

Francis Keenan, Shaun Bloomfield, Michail Mathioudakis, D.J. Christian, J.L. Linsky

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


In this paper we investigate the validity of the optically thin assumption in the transition region of the late-type star AU Mic. We use Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C III multiplet and O VI resonance lines, hence yielding information at two different levels within the atmosphere. Significant deviations from the optically thin fluxes are found for C III in both quiescent and flare spectra, where only 60% of the flux is actually observed. This could explain the apparent deviation of C III observed in emission measure distributions. We utilize escape probabilities for both homogeneous and inhomogeneous geometries and calculate optical depths as high as 10 for the C III 1175.71 Angstrom component of the multiplet. Using a lower limit to the electron density (10(11) cm(-3))we derive an effective thickness of
Original languageEnglish
Pages (from-to)219-224
Number of pages6
JournalAstronomy and Astrophysics
Issue number1
Publication statusPublished - Jul 2002

ASJC Scopus subject areas

  • Space and Planetary Science


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