A method for estimating tidal deformability of binary neutron stars in LIGO-Virgo detectors using minimal assumptions

Detection of gravitational waves (GW) from the binary neutron star (BNS) merger GW170817 provided an unprecedented probe for studying neutron stars’ (NS) astro- physics and fundamental physics. With only one detection, we were able to set constrains on the equation of state of neutron stars, issue an independent estimate of the Hubble constant and have a proof for the association of short gamma ray bursts (sGRB) with BNS mergers proving the importance of multi-messenger astrophysics. The GW signal of a BNS is divided into three parts: inspiral; merger; post-merger. The observation of each of these parts provides information about the internal structure of the NS that is still unknown. However, the ground based interferometers, considering the current sensitivity, are mainly sensitive to the late inspiral of the BNS GW signal. In the future, as sensitivity will increase, high SNR detections will make also merger and post merger observable. Nevertheless, the inspiral can last ' 100s in the detectors sensitive frequency band and carries important information about the nature of the NS. In fact, in this stage of the evolution of the system tidal interactions between the two stars rise a↵ecting the phase of the inspiral. The higher the tidal deformability, the faster the two stars merge. Measuring tidal deformability provides constraints on the NS equation of state. Therefore, the main goal of this thesis is to develop a method to constrain the tidal deformability parameter studying the match (fitting factor - FF) between theoretical and reconstructed waveforms. This method has been developed in the framework of coherent WaveBurst (cWB), a LIGO-Virgo pipeline to perform burst searches without assump- tions on the signal morphology. The first achievement of this method is to estimate the probability to reject the null tidal case given di↵erent values of the tidal parameter. This is possible for nearby events (d < 20Mpc) or, equivalently, at high SNRs (SNR 85). The second result is the possibility to estimate the tidal parameter with a credible inter- val given the point estimated FF of a set of random events with two and three detectors using the foreseen sensitivity of the third observing of the LIGO-Virgo detectors.