Gravity wave and model-independent axion
  In this short comment, we notice that the model-independent axion
contribution to the graviton mass at just outside the Schwarzschild radius is
completely negligible in GW150914. The model-independent axion contribution to
the graviton mass at the order $10^{-22}\,$eV might be possible for merger of
black holes of mass of order $2\times 10^{14}\,$kg.
