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Fe XIII Emission Lines Observed by EUVE and the S082A Instrument On-Board Skylab

Published online by Cambridge University Press:  12 April 2016

F.P. Keenan ,
J.J. Drake ,
V.J. Foster ,
C.J. Greer ,
S.S. Tayal  and
K.G. Widing
F.P. Keenan
Affiliation:
Department of Pure and Applied Physics, The Queen’s University of Belfast, Belfast BT7 INN, N.Ireland
J.J. Drake
Affiliation:
Center for EUV Astrophysics, 2150 Kittredge Street, University of California, Berkeley, CA 94720-5030, USA
V.J. Foster
Affiliation:
Department of Pure and Applied Physics, The Queen’s University of Belfast, Belfast BT7 INN, N.Ireland
C.J. Greer
Affiliation:
Department of Pure and Applied Physics, The Queen’s University of Belfast, Belfast BT7 INN, N.Ireland
S.S. Tayal
Affiliation:
Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, GA 30314, USA
K.G. Widing
Affiliation:
Code 4174W, E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington DC 20375, USA

Abstract

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Recent R-matrix calculations of electron impact excitation rates for Fe XIII are used to derive the theoretical electron density sensitive emission line ratios R1 = I(318.12 Å)/I(320.80 Å) and R2 = I(256.42 Å)/I(251.95 Å), which are found to be up to 50% different from earlier diagnostics. A comparison of the current line ratios with both solar flare and active region observations, obtained by the Naval Research Laboratory’s S082A spectrograph on board Skylab, reveals generally good agreement between densities deduced from Fe XIII and those estimated from diagnostic line ratios in species formed at similar temperatures. This provides experimental support for the accuracy of the line ratio calculations, and hence the atomic data adopted in their derivation. In Extreme Ultraviolet Explorer satellite (EUVE) spectra the Fe XIII emission lines are found to be severely blended. However, an analysis of these lines measured in the spectra of Procyon and α Cen demonstrates that they still allow very approximate values of the electron density to be inferred. Moreover, it should be possible to increase the accuracy of the measured line fluxes, and hence of the inferred densities, if longer exposures of the stars concerned can be obtained.

Type
XII. The Solar/Stellar Connection in the EUV
Information
International Astronomical Union Colloquium , Volume 152: Astrophysics in the Extreme Ultraviolet , 1996 , pp. 525 - 529
Copyright
Copyright © Kluwer 1996

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