科研之友
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摘要
We have analyzed 280 ks of co-added observations performed with Chandra's Low Energy Transmission Grating Spectrometer using theoretical spectra of Fe VIII through Fe XVII. The model spectral data were produced by combining collisional excitation data generated with the Flexible Atomic Code and transition energies generated with a relativistic code based on the multi-reference Moller-Plesset perturbation theory. The spectroscopic accuracy of the theoretical Fe IX wave lengths was ascertained in a comparison with existing laboratory measurements. We find several new Fe IX lines in the 100-140 angstrom region and confirm two previous identifications. We also have identified a new line from Fe X near 111 angstrom; several weak features near 102 angstrom may also be ascribed to Fe X. A line near 100.5 angstrom is identified as originating from Fe XI; a neighboring feature near 101 angstrom may also be from Fe XI. A cluster of three weak lines between 117 and 118 angstrom may be ascribed to Fe XII. Two lines near 104 and 106 angstrom, respectively, have been assigned to Fe XIII. In addition, we confirmed the presence of two out of four Fe VIII lines that were thought to exist in the spectrum. These two lines are located near 131 angstrom. The Fe IX emission is weakly sensitive to the assumed electron density, while the Fe XIII is strongly dependent on density. We find that a density between 109 and 1010 cm(-3) provides the best fit to the Procyon spectrum. We note that several of the new identifications have come at the expense of prior assignments to magnesium or calcium lines, removing evidence for the presence of these elements in this spectral region. No evidence for Fe XVIII, Fe XIX, or Fe XX was found.
- 出版日期2014-2
