2010 (IPP)
Permanent URI for this collectionhttp://localhost:4000/handle/11007/152
Browse
Item Coherent versus coincidence detection of gravitational wave signals from compact inspiraling binaries(2010-03-30) Dhurandhar, Sanjeev; Mukhopadhyay, Himan; Tagoshi, H.; et al.We compare two multi-detector detection strategies, namely, the coincidence and the coherent, for the detection of spinless inspiraling compact binary gravitational wave (GW) signals. The coincident strategy treats the detectors as if they are isolated - com- pares individual detector statistics with their respective thresholds while the coherent strategy combines the detector network data phase coherently to obtain a single detection statistic which is then compared with a single threshold. In the case of geographically separated detectors, we also consider an enhanced coincidence strategy because the usual (naive) coincidence strategy yields poor results for misaligned detectors. For simplicity, we consider detector pairs having the same power spectral density of noise, as that of initial LIGO and also assume the noise to be stationary and Gaussian. We compare the performances of the methods by plotting the receiver operating characteristic (ROC) for the two strategies. A single astrophysical source as well as a distribution of sources is considered. We find that the coherent strategy performs better than the two coincident strategies under the assumptions of stationary Gaussian detector noise.Item Group theoretic approach to detecting gravitational waves from asymmetric rotating neutron stars(2010-10-12) Dhurandhar, Sanjeev; Krishnan, B.The era of advanced ground based interferometric detectors of gravitational waves (GW) has arrived. These detectors are expected to go line in six years or so from now and which will have requisite sensitivity for detecting and observing astrophysical gravitational wave sources. In this article we will focus on a specific GW source, the GWs emitted by an isolated rotating neutron star/pulsar, and describe a novel approach to address this highly com- putationally intensive problem. We will describe how the symmetries in the model can be potentially used to reduce the computational effort.Item Time delay interferometry for LISA with one arm dysfunctional(2010-01-27) Dhurandhar, Sanjeev; Nayak, K. R.; Vinet, J-Y.In order to attain the requisite sensitivity for LISA - a joint space mission of the ESA and NASA- the laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. By combining six appropriately time-delayed data streams containing fractional Doppler shifts - a technique called time delay interferometry (TDI) - the laser frequency noise may be adequately suppressed. We consider the general model of LISA where the armlengths vary with time, so that second generation TDI are relevant. However, we must envisage the possibility, that not all the optical links of LISA will be operating at all times, and therefore, we here consider the case of LISA operating with two arms only. As shown earlier in the literature, obtaining even approximate solutions of TDI to the general problem is very difficult. Since here only four optical links are relevant, the algebraic problem simplifies considerably. We are then able to exhibit a large number of solutions (from mathematical point of view an infinite number) and further present an algorithm to generate these solutions.