Modified Gravity and the Flux-weighted Gravity-Luminosity Relationship
  of Blue Supergiant Stars
  We calculate models of stellar evolution for very massive stars and include
the effects of modified gravity to investigate the influence on the physical
properties of blue supergiant stars and their use as extragalactic distance
indicators. With shielding and fifth force parameters in a similar range as in
previous studies of Cepheid and tip of the red giant branch (TRGB) stars we
find clear effects on stellar luminosity and flux-weighted gravity. The
relationship between flux weighted gravity, g_F = g/Teff^4, and bolometric
magnitude M_bol (FGLR), which has been used successfully for accurate distance
determinations, is systematically affected. While the stellar evolution FGLRs
show a systematic offset from the observed relation, we can use the
differential shifts between models with Newtonian and modified gravity to
estimate the influence on FGLR distance determinations. Modified gravity leads
to a distance increase of 0.05 to 0.15 magnitudes in distance modulus. These
change are comparable to the ones found for Cepheid stars. We compare observed
FGLR and TRGB distances of nine galaxies to constrain the free parameters of
modified gravity. Not accounting for systematic differences between TRGB and
FGLR distances shielding parameters of 5*10^-7 and 10^-6 and fifth force
parameters of 1/3 and 1 can be ruled out with about 90% confidence. Allowing
for potential systematic offsets between TRGB and FGLR distances no
determination is possible for a shielding parameter of 10^-6. For 5*10$^-7 a
fifth force parameter of 1 can be ruled out to 92% but 1/3 is unlikely only to
60%.
