Studies on Newtonian chirp from inspiraling compact binaries
Department of Theoretical Physics, University of Madras
In this article we study the gravitational waves produced from inspiral phase of compact binaries in circular orbit using the Newtonian chirp of leading order post-Newtonian(PN) approximation. Expressions governing the Newtonian chirp are useful for obtaining the inspiral waveform, frequency variation plot, merging time value and to plot the amplitude spectral density. We start with the discussion of Newtonian chirp, where we assume the compact binaries to be located at galactic center to obtain the waveform and frequency variation plots. For the singular value of peak frequency seen at end of inspiral phase in Newtonian chirp, the concept of gravitational wave frequency corresponding to inner most stable circular orbit(ISCO) provided by general relativity is described. The qualitative differences observed in chirp duration and frequency evolution of these systems is explained. We also take the GW150914 event parameters reported by LIGO team to obtain the inspiral waveform from Newtonian chirp with F_ISCO as inspiral limit and overlay on LIGO discovered full waveform to show the merger and ringdown phase of a real signal. We plot the amplitude spectral density of various compact binaries along with GW150914 and GW151226 events and overlay it on LIGO and aLIGO sensitivity curve; it establishes the merging events and possible distances which can be detected in detectors. We also give a brief discussion on the supermassive black hole binary and slowly orbiting binary systems. We also bring out the contribution of higher order PN terms to number of cycles for various compact binaries. Inferences are drawn from these studies which reveals useful insights and information.