Measuring neutron star distances and properties with gravitational-wave parallax

Gravitational-wave astronomy allows us to study objects and events invisible to electromagnetic waves. So far, only signals triggered by coalescing binaries have been detected. However, as the interferometers' sensitivities improve over time, we expect to observe weaker signals in the future, e.g. emission of continuous gravitational waves from spinning, isolated neutron stars. Parallax is a well-known method, widely used in electromagnetic astronomical observations, to estimate the distance to a source. In this work, we consider the application of the parallax method to gravitational-wave searches and explore possible distance estimation errors. We show that detection of parallax in the signal from a spinning down source can constrain the neutron star moment of inertia. For instance, we found that the relative error of the moment of inertia estimation is smaller than 10 per cent for all sources closer than 300 pc, for the assumed birth frequency of 700 Hz, ellipticity >= 10(-7), and for 2 yr of observations by the Einstein Telescope, assuming spin-down due purely to quadrupolar gravitational radiation.

Automated summary

Gravitational-wave astronomy allows us to study invisible objects and events. The improvement in sensitivities of interferometers will enable the detection of weaker signals, such as the emission of continuous gravitational waves. By applying the well-known parallax method, we can estimate the distance to gravitational-wave sources and explore potential errors. The study shows that detecting parallax in signals from spinning down sources can provide constraints on neutron star moment of inertia estimations.