Searching for Gravitational Waves from Sub-Solar Mass Black Holes

Abstract

We are searching for gravitational-wave signals from sub-solar mass black hole binary systems in initial Laser Interferometer Gravitational-wave Observatory (LIGO) data. The most likely candidates for such systems are primordial black holes that have formed from the collapse of quantum fluctuations in the early universe. Primordial black holes have not yet been ruled out by microlensing experiments, but the allowable masses have been restricted. The gravitational- wave strain from such an inspiralling binary system is well modeled with the post- Newtonian formalism. Therefore, a modeled search for gravitational-wave signals is employed. The search technique is known as matched filtering and is implemented using a codebase that is well-suited for fast searches with long signals. One of the biggest challenges in performing this search is dealing with the heavy computational burden. The gravitational-wave signals from such low-mass binary systems are long (about 10 minutes) and require a large number of models, or templates, spread across the parameter space. A large effort has been focused on speeding up the search while using a reasonable amount of computational resources.