134 research outputs found
Searching for Massive Black Hole Binaries in the first Mock LISA Data Challenge
The Mock LISA Data Challenge is a worldwide effort to solve the LISA data
analysis problem. We present here our results for the Massive Black Hole Binary
(BBH) section of Round 1. Our results cover Challenge 1.2.1, where the
coalescence of the binary is seen, and Challenge 1.2.2, where the coalescence
occurs after the simulated observational period. The data stream is composed of
Gaussian instrumental noise plus an unknown BBH waveform. Our search algorithm
is based on a variant of the Markov Chain Monte Carlo method that uses
Metropolis-Hastings sampling and thermostated frequency annealing. We present
results from the training data sets and the blind data sets. We demonstrate
that our algorithm is able to rapidly locate the sources, accurately recover
the source parameters, and provide error estimates for the recovered
parameters.Comment: 11 pages, 6 figures, Submitted to CQG proceedings of GWDAW 11, AEI,
Germany, Dec 200
Detecting Galactic Binaries with LISA
One of the main sources of gravitational waves for the LISA space-borne
interferometer are galactic binary systems. The waveforms for these sources are
represented by eight parameters, of which four are extrinsic, and four are
intrinsic to the system. Geometrically, these signals exist in an 8-d parameter
space. By calculating the metric tensor on this space, we calculate the number
of templates needed to search for such sources. We show in this study that
below a particular monochromatic frequency, we can ignore one of the intrinsic
parameters and search over a 7-d space. Beyond this frequency, we have a sudden
change in dimensionality of the parameter space from 7 to 8 dimensions, which
results in a change in the scaling of the growth of template number as a
function of monochromatic frequency.Comment: 7 pages-2 figures. One figure added and typos corrected. Accepted for
the proceedings of GWDAW 9, special edition of Classical and Quantum Gravit
Catching Super Massive Black Hole Binaries Without a Net
The gravitational wave signals from coalescing Supermassive Black Hole
Binaries are prime targets for the Laser Interferometer Space Antenna (LISA).
With optimal data processing techniques, the LISA observatory should be able to
detect black hole mergers anywhere in the Universe. The challenge is to find
ways to dig the signals out of a combination of instrument noise and the large
foreground from stellar mass binaries in our own galaxy. The standard procedure
of matched filtering against a grid of templates can be computationally
prohibitive, especially when the black holes are spinning or the mass ratio is
large. Here we develop an alternative approach based on Metropolis-Hastings
sampling and simulated annealing that is orders of magnitude cheaper than a
grid search. We demonstrate our approach on simulated LISA data streams that
contain the signals from binary systems of Schwarzschild Black Holes, embedded
in instrument noise and a foreground containing 26 million galactic binaries.
The search algorithm is able to accurately recover the 9 parameters that
describe the black hole binary without first having to remove any of the bright
foreground sources, even when the black hole system has low signal-to-noise.Comment: 4 pages, 3 figures, Refined search algorithm, added low SNR exampl
MCMC Exploration of Supermassive Black Hole Binary Inspirals
The Laser Interferometer Space Antenna will be able to detect the inspiral
and merger of Super Massive Black Hole Binaries (SMBHBs) anywhere in the
Universe. Standard matched filtering techniques can be used to detect and
characterize these systems. Markov Chain Monte Carlo (MCMC) methods are ideally
suited to this and other LISA data analysis problems as they are able to
efficiently handle models with large dimensions. Here we compare the posterior
parameter distributions derived by an MCMC algorithm with the distributions
predicted by the Fisher information matrix. We find excellent agreement for the
extrinsic parameters, while the Fisher matrix slightly overestimates errors in
the intrinsic parameters.Comment: Submitted to CQG as a GWDAW-10 Conference Proceedings, 9 pages, 5
figures, Published Versio
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
Creating Social Legacy: Flow in Mega Event Ceremonies
The paper offers a novel conceptual framework linking narrative, attention, immersion, and flow as antecedents of social legacy using examples of polysemic events, such as mega event ceremonies. By doing this the paper uses a multidisciplinary approach to conceptualise the connection between narrative and social legacy, a relationship currently overlooked. Through the creation of this framework, we propose several key findings. First, narrative within polysemic events is useful for creating a targeted social legacy. This happens when the consumer’s attention is caught and maintained by the narrative, allowing them to become immersed in their experience. Second, we suggest that to optimise this process, the narrative must position consumers within a state of flow. Once in this state of flow, the individual’s goals shift to reflect that of the narrative thus contributing to social legacy. In proposing this framework, this paper makes a valuable contribution by addressing the surprisingly overlooked links between narrative, flow, and social legacy. Using the case of ceremonies, the paper also adds to the limited literature surrounding the social legacy of mega events, currently dominated by economic perspectives
Data Analysis Challenges for the Einstein Telescope
The Einstein Telescope is a proposed third generation gravitational wave
detector that will operate in the region of 1 Hz to a few kHz. As well as the
inspiral of compact binaries composed of neutron stars or black holes, the
lower frequency cut-off of the detector will open the window to a number of new
sources. These will include the end stage of inspirals, plus merger and
ringdown of intermediate mass black holes, where the masses of the component
bodies are on the order of a few hundred solar masses. There is also the
possibility of observing intermediate mass ratio inspirals, where a stellar
mass compact object inspirals into a black hole which is a few hundred to a few
thousand times more massive. In this article, we investigate some of the data
analysis challenges for the Einstein Telescope such as the effects of increased
source number, the need for more accurate waveform models and the some of the
computational issues that a data analysis strategy might face.Comment: 18 pages, Invited review for Einstein Telescope special edition of
GR
Low-frequency gravitational-wave science with eLISA/NGO
We review the expected science performance of the New Gravitational-Wave
Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space
Agency for launch in the early 2020s. eLISA will survey the low-frequency
gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a
broad variety of systems and events throughout the Universe, including the
coalescences of massive black holes brought together by galaxy mergers; the
inspirals of stellar-mass black holes and compact stars into central galactic
black holes; several millions of ultracompact binaries, both detached and mass
transferring, in the Galaxy; and possibly unforeseen sources such as the relic
gravitational-wave radiation from the early Universe. eLISA's high
signal-to-noise measurements will provide new insight into the structure and
history of the Universe, and they will test general relativity in its
strong-field dynamical regime.Comment: 20 pages, 8 figures, proceedings of the 9th Amaldi Conference on
Gravitational Waves. Final journal version. For a longer exposition of the
eLISA science case, see http://arxiv.org/abs/1201.362
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