Measuring chemical evolution and gravitational dependence of α using ultraviolet Fe v and Ni v transitions in white-dwarf spectra

Abstract

In this paper, we present the details of the ab initio high-precision configuration interaction and many-body perturbation theory calculations that were used by Berengut [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.111.010801 111, 010801 (2013)] to place limits on the dependence of the fine-structure constant, α, on the gravitational field of the white-dwarf star G191-B2B. These calculations were combined with laboratory wavelengths and spectra from the Hubble Space Telescope Imaging Spectrograph to obtain the result Δα/α=(4.2±1.6)×10^-5 and (-6.1±5.8)×10^-5 using Fe v and Ni v transitions, respectively. The uncertainty in these results are dominated by the uncertainty in the laboratory wavelengths. In this work we also present ab initio calculations of the isotopic shifts of the Fe v transitions. We show that improved laboratory spectra will enable determination of the relative isotope abundances in Fe v to an accuracy of ∼20%. Therefore this work provides a strong motivation for new laboratory measurements.