Advances in Stellar Astrophysics from Laboratory Spectroscopy

University dissertation from Stefan Ivarsson, Box 43, 221 00, Lund

Abstract: Investigation of astrophysical plasmas, such as stellar atmospheres, require both knowledge of atomic structure and data. We present laboratory instruments, techniques and tools for acquisition of the data required to derive important atomic parameters such as, wavelengths, oscillator strengths and line profiles. In this thesis new atomic data for advancement of stellar atmosphere analysis are presented for the elements iridium, osmium, praseodymium and uranium. These measurements were recorded with the Fourier Transform spectrometer (FTS) in Lund. Utilizing the high resolving power of the FTS we have derived magnetic hyperfine structure constants, A-values, for the singly-ionized species of praseodymium. Combining A with f-values, generating a hyperfine line profile, we have investigated the solar photospheric abundance of praseodymium by means of a synthetic spectrum technique. We conclude the abundance value to be significantly lower than the current canonical value. We investigate the possibility of using Os I and Ir I as the stable reference elements for age determination of the halo-star CS 31082-001 by use of cosmochrometers. Presentation and usage of new oscillator strengths solve the apparent over abundance of osmium compared with iridium and conclude that they originate from the same r-process nucleosynthesis. Observations in the ultraviolet region by Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) have shown increased need for production of atomic data. We present atmospheric analyses for the stars Chi Lupi and 17 Comae A regarding elemental abundances in the UV region. The onset of the heavy 5d element peak for Chi Lupi is defined with the presented new f-values for Os II and Ir II. The nature of the advancement, common for each project, is the inclusion of newer and improved atomic data to meet the demands from astronomical observations. Interpretation of stellar spectra, based upon these inclusions, advance our understanding and put constraints on our models of stellar atmospheres.

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