Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999head....4.0907b&link_type=abstract
American Astronomical Society, HEAD meeting #4, #09.07; Bulletin of the American Astronomical Society, Vol. 31, p.706
Astronomy and Astrophysics
Astronomy
Scientific paper
The line emission of Fe vii through Fe x ions in the extreme ultraviolet region below 140 Angstroms has been measured in controlled laboratory experiments under conditions representative of stellar coronae. The observations are compared to predictions from standard spectral models. We find that the atomic data bases, including CHIANTI, which claimed to be ``essentially complete for specifying the emission spectrum at wavelengths greater than 50 Angstroms,'' are woefully incomplete and do not adequately reproduce the wealth of observed lines of the type 3l - nl'. While some of these lines missing from the models form isolated features, most msising lines are unresolved and add to form a quasi-continuum in the 60--120 Angstroms region. This incompleteness can explain the poor fit of short-wavelength data from cool stars, such as alpha -Cen, measured by the Extreme Ultraviolet Explorer satellite, the origin of which has been a source of controversy since the original observations were made. Additional laboratory measurements are being carried out involving the emission from the higher charge states of iron. The measured spectra are guiding the development of improved atomic data sets and will serve as a laboratory benchmark for comparison with the data collected as part of the X-ray Emission Line Project (XELP) that will be carried out during the first phase of the upcoming Chandra X-ray Observatory mission. 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.
Beiersdorfer Peter
Brown Gregory V.
Kahn Steve M.
Lepson J. K.
Liedahl Duane Allen
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