Searches for cosmicstring gravitationalwave bursts in Mock LISA Data
Abstract
A network of observable, macroscopic cosmic (super)strings may well have formed in the early Universe. If so, the cusps that generically develop on cosmicstring loops emit bursts of gravitational radiation that could be detectable by gravitationalwave interferometers, such as the groundbased LIGO/Virgo detectors and the planned, spacebased LISA detector. Here we report on two versions of a LISAoriented stringburst search pipeline that we have developed and tested within the context of the Mock LISA Data Challenges. The two versions rely on the publicly available MultiNest and PyMC software packages, respectively. To reduce the effective dimensionality of the search space, our implementations use the Fstatistic to analytically maximize over the signal's amplitude and polarization, \mathcal {A} and ψ, and use the FFT to search quickly over burst arrival times t_{C}. The standard Fstatistic is essentially a frequentist statistic that maximizes the likelihood; we also demonstrate an approximate, Bayesian version of the Fstatistic that incorporates realistic priors on \mathcal {A} and ψ. We calculate how accurately LISA can expect to measure the physical parameters of stringburst sources, and compare to results based on the Fishermatrix approximation. To understand LISA's angular resolution for stringburst sources, we draw maps of the waveform fitting factor (maximized over (\mathcal {A}, \psi, t_C)) as a function of the sky position; these maps dramatically illustrate why (for LISA) inferring the correct sky location of the emitting string loop will often be practically impossible. In addition, we identify and elucidate several symmetries that are imbedded in this search problem, and we derive the distribution of cutoff frequencies f_{max} for observable bursts.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 September 2010
 DOI:
 10.1088/02649381/27/18/185012
 arXiv:
 arXiv:1002.4153
 Bibcode:
 2010CQGra..27r5012C
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 Final CQG version