Probing the Gravitational Dependence of the Fine-Structure Constant from
  Observations of White Dwarf Stars
  Hot white dwarf stars are the ideal probe for a relationship between the
fine-structure constant and strong gravitational fields, providing us with an
opportunity for a direct observational test. We study a sample of hot white
dwarf stars, combining far-UV spectroscopic observations, atomic physics,
atmospheric modelling and fundamental physics, in the search for variation in
the fine structure constant. This variation manifests as shifts in the observed
wavelengths of absorption lines, such as quadruply ionized iron (FeV) and
quadruply ionized nickel (NiV), when compared to laboratory wavelengths.
Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity
of such an analysis using high-resolution Hubble Space Telescope (HST)/Space
Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three
important improvements by: (a) using three new independent sets of laboratory
wavelengths, (b) analysing a sample of objects, and (c) improving the
methodology by incorporating robust techniques from previous studies towards
quasars (the Many Multiplet method). A successful detection would be the first
direct measurement of a gravitational field effect on a bare constant of
nature. Here we describe our approach and present preliminary results from nine
objects using both FeV and NiV.
