HEAD Division Meeting 1999, April 1999
Session 9. Stellar Coronae
Poster, Monday, April 12, 1999, 8:30am-6:10pm, Gold Room

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[9.08] Cataloguing the Lines from the Intermediate Charge States of Iron, Fe{\sc vii} through Fe{\sc xxiv}, in the Extreme Ultraviolet below 150 \AA

J.K. Lepson (SSL), P. Beiersdorfer, G.V. Brown, D.A. Liedahl, C.W. Mauche, S.B. Utter (LLNL), S.M. Kahn (Columbia)

The problems encountered with fitting stellar line emission spectra in the short-wavelength EUV band measured by the Extreme Ultraviolet Explorer illustrate the need to improve the atomic data in the spectral models used for analysis. This need is becoming yet more pressing with the upcoming launch of the Chandra X-ray Observatory mission. To address this need, we have started to catalogue all emission lines from the intermediate charge states of iron (Fe{\sc vii} through Fe{\sc xxiv}) obtained in a controlled laboratory environment. We have completed detailed wavelength measurements of the 2--2 L-shell transitions of Fe{\sc xvii} through Fe{\sc xxiii} below 150 Å. These measurements comprise 22 lines, including some that have never been resolved before, which are measured with an accuracy of 15--40 mÅ. Good agreement is found with previous laboratory measurements, where available, establishing the reliability of our approach. Our measurements also include new wavelengths of Fe{\sc vii}, Fe{\sc viii}, and Fe{\sc ix} lines, which are measured with similar accuracy. Many of the lines from these low charge states are missing from the recently developed astrophysical atomic data bases, such as CHIANTI, MEKAL, and the Brickhouse-Raymond-Smith model. Analysis of Fe{\sc x} through Fe{\sc xvi} spectra is in progress, and preliminary data will be presented.

This work was supported by the National Aeronautics and Space Administration Optical, UV, and Gravitational Research and Analysis Program under grant NAG5-6731 and performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory under contract W-7405-ENG-48.

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