The role of astrophysical effects in testing general relativity with gravitational waves from double white dwarfs

Testing gravity beyond general relativity (GR) motivated by cosmological observations or quantum gravity has been of interest in theoretical physics. Although existing tests have provided stringent bounds on the discrepancies from GR, there is still plenty of room for certain theories to survive. Previous studies have shown that gravitational waves from galactic double white dwarfs can be a useful tool to constrain non-GR effects that are significant in relatively low-density regimes compared to neutron stars and black holes. Meanwhile, astrophysical effects such as self-rotations and tidal deformations also have a significant impact on the dynamics of these systems, thus adding complexity to the gravity tests. In this talk, I will present our study on the possible bounds we can place on the non-GR effects using gravitational waves from double white dwarfs. We employ a generic parametrized model for the non-GR corrections to the frequency evolution while taking into account the possible contaminations from astrophysical effects to estimate the bounds on the non-GR effect at different post-Newtonian order. We find that systematic errors due to the lack of astrophysical effects in waveform modeling can be comparable to statistical errors in certain cases. We also comment on how to apply this analysis to specific theories including the general screened modified gravity and theories involving axion, which are expected to deviate more from GR within white dwarfs than neutron stars and black holes.