New Fe I Level Energies and Line Identifications from Stellar Spectra
Abstract
The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain woefully incomplete, however, despite extensive laboratory and solar analysis. In this work, we use high-resolution archival absorption-line ultraviolet and optical spectra of stars whose warm temperatures favor moderate Fe I excitation. We derive the energy for a particular upper level in Kurucz's semiempirical calculations by adopting a trial value that yields the same wavelength for a given line predicted to be about as strong as that of a strong unidentified spectral line observed in the stellar spectra, then checking the new wavelengths of other strong predicted transitions that share the same upper level for coincidence with other strong observed unidentified lines. To date, this analysis has provided the upper energies of 66 Fe I levels. Many new energy levels are higher than those accessible to laboratory experiments; several exceed the Fe I ionization energy. These levels provide new identifications for over 2000 potentially detectable lines. Almost all of the new levels of odd parity include UV lines that were detected but unclassified in laboratory Fe I absorption spectra, providing an external check on the energy values. We motivate and present the procedure, provide the resulting new energy levels and their uncertainties, list all the potentially detectable UV and optical new Fe I line identifications and their gf values, point out new lines of astrophysical interest, and discuss the prospects for additional Fe I energy level determinations.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- January 2015
- DOI:
- 10.1088/0067-0049/216/1/1
- arXiv:
- arXiv:1406.0933
- Bibcode:
- 2015ApJS..216....1P
- Keywords:
-
- atomic data;
- line: identification;
- methods: laboratory: atomic;
- stars: individual: HD 29139 HD 72660 HD 76932 HD 85503 HD 94028 HD 124897 HD 140283 HD 157466 HD 160617 HD 165341 HD 184499 HD 211998 HD 217107;
- techniques: spectroscopic;
- ultraviolet: stars;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- v3 is the version submitted to the Astrophysical Journal Oct. 24, 2014, 10 pages, 3 tables, 5 figures, in response to the referee's report