Prospects for axion searches with Advanced LIGO through binary mergers
  The observation of gravitational waves from a binary neutron star merger by
LIGO/VIRGO and the associated electromagnetic counterpart provides a high
precision test of orbital dynamics, and therefore a new and sensitive probe of
extra forces and new radiative degrees of freedom. Axions are one particularly
well-motivated class of extensions to the Standard Model leading to new forces
and sources of radiation, which we focus on in this paper. Using an effective
field theory (EFT) approach, we calculate the first post-Newtonian corrections
to the orbital dynamics, radiated power, and gravitational waveform for binary
neutron star mergers in the presence of an axion. This result is applicable to
many theories which add an extra massive scalar degree of freedom to General
Relativity. We then perform a detailed forecast of the potential for Advanced
LIGO to constrain the free parameters of the EFT, and map these to the mass
$m_a$ and decay constant $f_a$ of the axion. At design sensitivity, we find
that Advanced LIGO can potentially exclude axions with $m_a \lesssim 10^{-11} \
{\rm eV}$ and $f_a \sim (10^{14} - 10^{17}) \ {\rm GeV}$. There are a variety
of complementary observational probes over this region of parameter space,
including the orbital decay of binary pulsars, black hole superradiance, and
laboratory searches. We comment on the synergies between these various
observables.
