IUCAA Preprints
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Item Search for gravitational waves from the millisecond pulsar PSR 0437-471(2015-03-11) Mohanty, S.D.; Heng, I.S.; Blair, D.G; Dhurandhar, S.V.; Tobar, M.; Ivanov, E.A search for gravitational waves from the millisecond pulsar PSR 0437-471has been initiated using the bar detector NIOBE which is located at the University of Western Australia. This search involves a very long coherent integration of the bar output which may stretch over a few years. We present a detailed report on the data analysis algorithm, called phase plane rotation,which will be used in this search. A discussion of the actual implementation of the algorithm is presented.Item Lensing by gravitational waves in scalar – tensor gravity: Einstein frame analysis(2015-03-11) Faraoni, Valerio; Gunzing , EdgardThe amplification of a light beam due to intervening gravitational waves is studied. The previous Jordan frame result according to which the amplification is many orders of magnitude larger in scalar-tensor gravity than in general relativity does not hold in the Einstein conformal frame. Lensing by gravitational waves is discussed in relation to the ongoing and proposed VLBI observations aimed at detecting the scintillation effect.Item A comparison of CMB lensing e ciency of gravitational waves and large scale structure(IUCAA, 2015-02) Padmanabhan, Hamsa; Rotti, Aditya; Tarun, SauradeepItem Hemispherical Asymmetry from Isotropy Violated Stochastic Gravitational Wave Background(IUCAA, 2015-02) Mukherjee, SuvodipItem Astrophysical motivation for directed searches for a stochastic gravitational wave background(IUCAA, 2015-02) Mazumder, Nairwita; Mitra, Sanjit; Dhurandhar, SanjeevItem Estimation of parameters of gravitational waves from coalescing binaries(2015-01-25) Balasubramanian, R.; Sathyaprakash, B.S.; Dhurandhar, S.V.Item Extended hierarchical search (EHS) algorithm for detection of gravitational waves from inspiraling compact binaries(2001-04-01) Sengupta, Anand; Dhurandhar, Sanjeev; Lazzarini, Albert; et al.Pattern matching techniques like matched filtering will be used for online extraction of gravitational wave signals buried inside detector noise. This involves cross correlating the detector output with hundreds of thousands of templates spanning a multi-dimensional parameter space, which is very expensive computationally. A faster implementation algorithm was devised by Mohanty and Dhurandhar [1996] using a hierarchy of templates over the mass parameters, which speeded up the procedure by about 25 to 30 times. We show that a further reduction in computational cost is possible if we extend the hierarchy paradigm to an extra parameter, namely, the time of arrival of the signal. In the first stage, the chirp waveform is cut-off at a relatively low frequency allowing the data to be coarsely sampled leading to cost saving in performing the FFTs. This is possible because most of the signal power is at low frequencies, and therefore the advantage due to hierarchy over masses is not compromised. Results are obtained for spin-less templates up to the second post-Newtonian (2PN) order for a single detector with LIGO I noise power spectral density. We estimate that the gain in computational cost over a flat search is about 100.Item Searching for gravitational waves from rotating neutron stars(2000-01-15) Dhurandhar, SanjeevRotating neutron stars are one of the important sources of gravitational waves (GW) for the ground based as well as space based detectors. Since the waves are emitted continuously, the source is termed as a continuous gravitational wave (CGW) source. The expected weakness of the signal requires long integration times ( year). The data analysis problem involves tracking the phase coherently over such large integration times, which makes it the most computationally intensive problem among all GW sources envisaged. In this article, the general problem of data analysis is discussed, and more so, in the context of searching for CGW sources orbiting another companion object. The problem is important because there are several pulsars, which could be deemed to be CGW sources orbiting another companion star. Differential geometric techniques for data analysis are described and used to obtain computational costs. These results are applied to known systems to assess whether such systems are detectable with current (or near future) computing resources.Item Searching for continuous gravitational wave sources in binary systems(2000-12-14) Dhurandhar, Sanjeev; Vecchio, AlbertoItem Gravitational wave astronomy : Recent advances(2002-05-30) Dhurandhar, SanjeevSeveral groundbased gravitational wave (GW) laser interferomet- ric projects have completed construction and are currently involved in conduct- ing engineering runs. The spacebased NASA-ESA mission, LISA is expected to be launched in ten years' time. With the data around the comer exciting times lie ahead for GW astronomy. A brief introduction to GW detection, the prin- ciple of GW detection, the current status of ground based detectors, the space based detector LISA, GW sources and the data analysis necessary to extract the weak GW signal from the detector noise will be presented