10,245 research outputs found
Search strategies for long gravitational-wave transients: hidden Markov model tracking and seedless clustering
A number of detections have been made in the past few years of gravitational
waves from compact binary coalescences. While there exist well-understood
waveform models for signals from compact binary coalescences, many sources of
gravitational waves are not well modeled, including potential long-transient
signals from a binary neutron star post-merger remnant. Searching for these
sources requires robust detection algorithms that make minimal assumptions
about any potential signals. In this paper, we compare two unmodeled search
schemes for long-transient gravitational waves, operating on cross-power
spectrograms. One is an efficient algorithm first implemented for continuous
wave searches, based on a hidden Markov model. The other is a seedless
clustering method, which has been used in transient gravitational wave analysis
in the past. We quantify the performance of both algorithms, including
sensitivity and computational cost, by simulating synthetic signals with a
special focus on sources like binary neutron star post-merger remnants. We
demonstrate that the hidden Markov model tracking is a good option in
model-agnostic searches for low signal-to-noise ratio signals. We also show
that it can outperform the seedless method for certain categories of signals
while also being computationally more efficient.Comment: 10 pages, 7 figure
Cosmic Swarms: A search for Supermassive Black Holes in the LISA data stream with a Hybrid Evolutionary Algorithm
We describe a hybrid evolutionary algorithm that can simultaneously search
for multiple supermassive black hole binary (SMBHB) inspirals in LISA data. The
algorithm mixes evolutionary computation, Metropolis-Hastings methods and
Nested Sampling. The inspiral of SMBHBs presents an interesting problem for
gravitational wave data analysis since, due to the LISA response function, the
sources have a bi-modal sky solution. We show here that it is possible not only
to detect multiple SMBHBs in the data stream, but also to investigate
simultaneously all the various modes of the global solution. In all cases, the
algorithm returns parameter determinations within (as estimated from
the Fisher Matrix) of the true answer, for both the actual and antipodal sky
solutions.Comment: submitted to Classical & Quantum Gravity. 19 pages, 4 figure
Hydra: A Parallel Adaptive Grid Code
We describe the first parallel implementation of an adaptive
particle-particle, particle-mesh code with smoothed particle hydrodynamics.
Parallelisation of the serial code, ``Hydra'', is achieved by using CRAFT, a
Cray proprietary language which allows rapid implementation of a serial code on
a parallel machine by allowing global addressing of distributed memory.
The collisionless variant of the code has already completed several 16.8
million particle cosmological simulations on a 128 processor Cray T3D whilst
the full hydrodynamic code has completed several 4.2 million particle combined
gas and dark matter runs. The efficiency of the code now allows parameter-space
explorations to be performed routinely using particles of each species.
A complete run including gas cooling, from high redshift to the present epoch
requires approximately 10 hours on 64 processors.
In this paper we present implementation details and results of the
performance and scalability of the CRAFT version of Hydra under varying degrees
of particle clustering.Comment: 23 pages, LaTex plus encapsulated figure
The PyCBC search for gravitational waves from compact binary coalescence
We describe the PyCBC search for gravitational waves from compact-object
binary coalescences in advanced gravitational-wave detector data. The search
was used in the first Advanced LIGO observing run and unambiguously identified
two black hole binary mergers, GW150914 and GW151226. At its core, the PyCBC
search performs a matched-filter search for binary merger signals using a bank
of gravitational-wave template waveforms. We provide a complete description of
the search pipeline including the steps used to mitigate the effects of noise
transients in the data, identify candidate events and measure their statistical
significance. The analysis is able to measure false-alarm rates as low as one
per million years, required for confident detection of signals. Using data from
initial LIGO's sixth science run, we show that the new analysis reduces the
background noise in the search, giving a 30% increase in sensitive volume for
binary neutron star systems over previous searches.Comment: 29 pages, 7 figures, accepted by Classical and Quantum Gravit
Time-frequency detection algorithm for gravitational wave bursts
An efficient algorithm is presented for the identification of short bursts of
gravitational radiation in the data from broad-band interferometric detectors.
The algorithm consists of three steps: pixels of the time-frequency
representation of the data that have power above a fixed threshold are first
identified. Clusters of such pixels that conform to a set of rules on their
size and their proximity to other clusters are formed, and a final threshold is
applied on the power integrated over all pixels in such clusters. Formal
arguments are given to support the conjecture that this algorithm is very
efficient for a wide class of signals. A precise model for the false alarm rate
of this algorithm is presented, and it is shown using a number of
representative numerical simulations to be accurate at the 1% level for most
values of the parameters, with maximal error around 10%.Comment: 26 pages, 15 figures, to appear in PR
Detecting compact binary coalescences with seedless clustering
Compact binary coalescences are a promising source of gravitational waves for
second-generation interferometric gravitational-wave detectors. Although
matched filtering is the optimal search method for well-modeled systems,
alternative detection strategies can be used to guard against theoretical
errors (e.g., involving new physics and/or assumptions about spin/eccentricity)
while providing a measure of redundancy. In previous work, we showed how
"seedless clustering" can be used to detect long-lived gravitational-wave
transients in both targeted and all-sky searches. In this paper, we apply
seedless clustering to the problem of low-mass ()
compact binary coalescences for both spinning and eccentric systems. We show
that seedless clustering provides a robust and computationally efficient method
for detecting low-mass compact binaries
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