Reconstruction of chirp mass in searches for gravitational wave transients

Transcription

1 Classical and Quantum Gravity LETTER Reconstruction of chirp mass in searches for gravitational wave transients To cite this article: V Tiwari et al Class. Quantum Grav. 0LT0 Manuscript version: Accepted Manuscript Accepted Manuscript is the version of the article accepted for publication including all changes made as a result of the peer review process, and which may also include the addition to the article by IOP Publishing of a header, an article ID, a cover sheet and/or an Accepted Manuscript watermark, but excluding any other editing, typesetting or other changes made by IOP Publishing and/or its licensors This Accepted Manuscript is IOP Publishing Ltd. During the embargo period (the month period from the publication of the Version of Record of this article), the Accepted Manuscript is fully protected by copyright and cannot be reused or reposted elsewhere. As the Version of Record of this article is going to be / has been published on a subscription basis, this Accepted Manuscript is available for reuse under a CC BY-NC-ND.0 licence after the month embargo period. After the embargo period, everyone is permitted to use copy and redistribute this article for non-commercial purposes only, provided that they adhere to all the terms of the licence Although reasonable endeavours have been taken to obtain all necessary permissions from third parties to include their copyrighted content within this article, their full citation and copyright line may not be present in this Accepted Manuscript version. Before using any content from this article, please refer to the Version of Record on IOPscience once published for full citation and copyright details, as permissions will likely be required. All third party content is fully copyright protected, unless specifically stated otherwise in the figure caption in the Version of Record. View the article online for updates and enhancements. This content was downloaded from IP address... on /0/ at 0:

2 Manuscript version: Accepted Manuscript The Accepted Manuscript is the author s original version of an article including any changes made following the peer review process but excluding any editing, typesetting or other changes made by IOP Publishing and/or its licensors. During the embargo period (the month period from publication of the Version of Record of this article), the Accepted Manuscript: is fully protected by copyright and can only be accessed by subscribers to the journal; cannot be reused or reposted elsewhere by anyone unless an exception to this policy has been agreed in writing with IOP Publishing As the Version of Record of this article is going to be/has been published on a subscription basis, this Accepted Manuscript will be available for reuse under a CC BY-NC-ND.0 licence after a month embargo period. After the embargo period, everyone is permitted to copy and redistribute this article for Non-Commercial purposes only, provided they*: give appropriate credit and provide the appropriate copyright notice; show that this article is published under a CC BY-NC-ND.0 licence; provide a link to the CC BY-NC-ND.0 licence; provide a link to the Version of Record; do not use this article for commercial advantage or monetary compensation; and only use this article in its entirety and do not make derivatives from it. *Please see CC BY-NC-ND.0 licence for full terms. View the Version of Record for this article online at iopscience.org This content was downloaded from IOPscience

3 Page of CONFIDENTIAL - AUTHOR SUBMITTED MANUSCRIPT CQG-.R Reconstruction of Chirp Mass in Searches for Gravitational Wave Transients V. Tiwari, S. Klimenko, V. Necula, and G. Mitselmakher University of Florida, P.O.Box, Gainesville, Florida,, USA (Dated: November, ) Excess energy method is used in searches for gravitational waves (GWs) produced by sources with poorly modelled characteristics. It identifies GW events by searching for a coincident excess energy in a GW detector network. While it is sensitive to a wide range of signal morphologies, the energy outliers can be populated by background noise events (background), thereby reducing the statistical confidence of a true signal. However, if the physics of the source is partially understood, weak model dependent constraints can be imposed to suppress the background. This letter presents a novel idea of using the reconstructed chirp mass along with two goodness of fit parameters for suppressing background when search is focused on GW produced from the compact binary coalescence. PACS numbers:..sz, 0.0.Nn I. INTRODUCTION Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment targeting the first direct detection and study of gravitational waves from astrophysical sources []. Two LIGO detectors in Livingston, LA and Hanford, WA have been upgraded to increase their sensitivity by an order of magnitude and started to take data in September. LIGO data is searched for GW signals by using matched filtering technique when GW waveforms of the source can be modeled. Furthermore, if source model is not understood or it is computationally or scientifically challenging to model waveforms, excess energy methods (aka burst method ) are used in the analysis. Coherent WaveBurst (cwb) method [] has been used to conduct multiple searches in the past [ ]. This method identify GW events by searching for a coincident appearance of excess energy in multiple GW detectors. The cwb parameter space is not constrained by the source models and covers a broad range of signal morphologies. Because of that, the cwb method is affected by background noises, which can be suppressed by providing the search an additional discriminating power [].This can be done by the application of weak model based constraints. In the presented letter we describe the event selection criteria based on the reconstructed chirp mass (addressed as chirp cut from henceforth) in a burst search for compact binary coalescence (CBC) sources. Reconstructed chirp mass along with two goodness of fit parameters is shown to greatly suppresses the background while keeping the robustness of the search intact. This letter is organized as follows: In Section II we describe the algorithm used for the reconstruction of the chirp mass; in Section III we discuss the application of the algorithm; results are discussed in Section IV and paper is concluded in Section V. II. ALGORITHM At the leading post-newtonian order, the frequency evolution of GW from a coalescing binary is given by Equation. f = ( ) / GMc π/ c f /, (.) wherem c = (m m ) / /(m +m ) / isthechirpmassof the binary with component masses m and m, G is the gravitational constant, and c is the speed of light [, ]. Integrating Equation. with respect to time gives, π/ ( GMc c ) / t+ f / +C = 0, (.) where C is the constant of integration. Furthermore, on identifying x t and y f /, the chirp mass can be calculated from the slope of the line fitted through the data points (x, y). In our case, the line fitting is performed on a collection of time-frequency (TF) pixels extracted from an excess energy event appearing in the detector network data. The center of the pixels are promoted as the data points by including dimension of the pixels ( f and t) as errors in the χ, defined as: χ i χ i, χ i = (y i b(x i x 0 )) Fi +b t, (.) i where F i = f / i f, b = (/)π /( GM c /c ) / and x 0 = C/b. The value of χ measures the quality of the fitted line, which has the slope b and the intercept C. The values for b and C are scanned for which the number of intersecting data points is maximum. If a data point has a χ i value of less than, it is counted towards the intersecting points. The value has been hand picked. A larger value will increase the number of intersecting data points as it will also consider distant data points from Gaussian noise and hence may not achieve a good

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