We propose a new probe of the dependence of the fine structure constant, alpha, on a strong gravitational field using metal lines in the spectra of white dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits on the fractional variation of alpha of (Delta alpha/alpha)=(4.2 +- 1.6)x10^(-5) and (-6.1 +- 5.8)x10^(-5) from Fe V and Ni V spectra, respectively, at a dimensionless gravitational potential relative to Earth of (Delta phi) ~ 5x10^(-5). With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to two orders of magnitude.
@article{arxiv.1305.1337,
title = {Limits on the dependence of the fine-structure constant on gravitational potential from white-dwarf spectra},
author = {J. C. Berengut and V. V. Flambaum and A. Ong and J. K. Webb and John D. Barrow and M. A. Barstow and S. P. Preval and J. B. Holberg},
journal= {arXiv preprint arXiv:1305.1337},
year = {2013}
}