Searching for Continuous Gravitational Waves from Unknown Isolated Neutron Stars in Advanced LIGO Data

Abstract

With the advent of the advanced gravitational wave detector era, the Laser Interferometer Gravitational-wave Observatory (LIGO) has made several detections of gravitational waves from coalescing binary black holes and binary neutron stars, but other sources are also predicted to exist. Among these are continuous waves from isolated neutron stars. This type of signal is expected to be significantly weaker than the sources observed so far, but to last for years. In this work we discuss the efforts and obstacles involved in searching for continuous gravitational waves. In particular, we give details of the PowerFlux analysis pipeline and evaluate its performance compared to other pipelines. We also discuss searches in the first observing run of Advanced LIGO, including methods for mitigating the effects of the many spectral noise lines present at low frequencies. Finally, we discuss approximations to the barycentering routines used by LIGO to account for the Earth's motion, approximations that provide justification for more computationally efficient loosely coherent searches.