Torsion-bar antenna in the proper reference frame with rotation

The resultant response of the rotating torsion-bar antenna for gravitational waves discussed in M. Ando et al. [Phys. Rev. Lett. 105, 161101 (2010)] is reinvestigated from a general-relativistic point of view. To do this, the equation of motion of a free-falling particle in the proper reference frame of a rotating observer is used. As a result, the resultant response derived in the above paper is also valid even when ${\omega }_g\sim \mathrm{\Omega }$, where ${\omega }_g$ and $\mathrm{\Omega }$ are the angular frequencies of gravitational waves and the rotation of the antenna, respectively.