Context Astrophysical observations play a critical role in the possibility of variations in fundamental physical constants. One of the ways of probing these variations would be based on the evolution of the white-dwarf stars.
Aims We use the spectrum of white-dwarf star G191-B2B to find an upper limit on the possible deviation of the gravitational constant with strong gravitational fields.
Methods We analyze archive observation of the Hubble Space Telescope Imaging Spectrograph (HSTIS) to determine the possible cosmological deviation of the gravitational constant from the observed gravitational redshift.
Results Our analysis provided a strong estimate on an upper bound on the possible space-time variation of the gravitational constant ̇⁄ = (0.238 ± 2.959) × 10 yr comparing with previous results.
Conclusions The obtained result in this study offers the possibility of testing parameters of modern unification theories.