1,063 research outputs found
Exploring a search for long-duration transient gravitational waves associated with magnetar bursts
Soft gamma repeaters and anomalous X-ray pulsars are thought to be magnetars,
neutron stars with strong magnetic fields of order --. These objects emit intermittent bursts
of hard X-rays and soft gamma rays. Quasiperiodic oscillations in the X-ray
tails of giant flares imply the existence of neutron star oscillation modes
which could emit gravitational waves powered by the magnetar's magnetic energy
reservoir. We describe a method to search for transient gravitational-wave
signals associated with magnetar bursts with durations of 10s to 1000s of
seconds. The sensitivity of this method is estimated by adding simulated
waveforms to data from the sixth science run of Laser Interferometer
Gravitational-wave Observatory (LIGO). We find a search sensitivity in terms of
the root sum square strain amplitude of for a half sine-Gaussian waveform with a central
frequency and a characteristic time . This corresponds to a gravitational wave energy of
, the same order of
magnitude as the 2004 giant flare which had an estimated electromagnetic energy
of , where is the distance to SGR 1806-20. We
present an extrapolation of these results to Advanced LIGO, estimating a
sensitivity to a gravitational wave energy of for a magnetar at a distance of .
These results suggest this search method can probe significantly below the
energy budgets for magnetar burst emission mechanisms such as crust cracking
and hydrodynamic deformation
Deep Multi-view Models for Glitch Classification
Non-cosmic, non-Gaussian disturbances known as "glitches", show up in
gravitational-wave data of the Advanced Laser Interferometer Gravitational-wave
Observatory, or aLIGO. In this paper, we propose a deep multi-view
convolutional neural network to classify glitches automatically. The primary
purpose of classifying glitches is to understand their characteristics and
origin, which facilitates their removal from the data or from the detector
entirely. We visualize glitches as spectrograms and leverage the
state-of-the-art image classification techniques in our model. The suggested
classifier is a multi-view deep neural network that exploits four different
views for classification. The experimental results demonstrate that the
proposed model improves the overall accuracy of the classification compared to
traditional single view algorithms.Comment: Accepted to the 42nd IEEE International Conference on Acoustics,
Speech and Signal Processing (ICASSP'17
Optimization of the configuration and working fluid for a micro heat pipe thermal control device
Continued development of highly compact and powerful electronic components
has led to the need for a simple and effective method for controlling the thermal
characteristics of these devices. One proposed method for thermal control involves
the use of a micro heat pipe system containing a working fluid with physical properties
having been speciffcally selected such that the heat pipes, as a whole, vary in effective
thermal conductance, thereby providing a level of temperature regulation. To further
explore this possibility, a design scenario with appropriate constraints was established
and a model developed to solve for the effective thermal conductance of individual
heat pipes as a function of evaporator-end temperature. From the results of this
analysis, several working fluids were identified and selected from a list over thirteen
hundred that were initially analyzed. Next, a thermal circuit model was developed
that translated the individual heat pipe operating characteristics into the system as a
whole to determine the system level effects. It was found that none of the prospective
fluids could completely satisfy the established design requirements to regulate the
device temperature over the entire range of operating conditions. This failure to
fully satisfy design requirements was due, in large part, to the highly constrained
nature of problem definition. Several fluids, however, did provide for an improved
level of thermal control when compared to the unmodified design. Suggestions for improvements that may lead to enhanced levels of thermal control are offered as well
as areas that are in need of further research
Gravity Spy and X-Pypeline: A multidisciplinary approach to characterizing and understanding non-astrophysical gravitational wave data and its impact on searches for unmodelled signals
With the first direct detection of gravitational waves, the Advanced Laser Interferometer
Gravitational-wave Observatory (aLIGO) has initiated a new field of astronomy
by providing an alternate means of sensing the Universe. The extreme sensitivity
required to make such detections is achieved through exquisite isolation of all
sensitive components of aLIGO from non-gravitational-wave disturbances. Nonetheless,
aLIGO is still susceptible to a variety of instrumental and environmental sources
of noise that contaminate the data. Of particular concern are noise features known
as glitches, which are transient and non-Gaussian in their nature, and occur at a high
enough rate that the possibility of accidental coincidence between the two aLIGO detectors
is non-negligible. Glitches come in a wide range of time-frequency-amplitude
morphologies, with new morphologies appearing as the detector evolves. Since they
can obscure or mimic true gravitational-wave signals, a robust characterization of
glitches is paramount in the effort to achieve the gravitational-wave detection rates
that are allowed by the design sensitivity of aLIGO. For this reason, over the past
few years, glitch classification techniques have been developed to help make this
task easier. Specifically, I explore the effect of glitches, and their suppression, on
key gravitational-wave searches such as that for a Galactic supernova. Moreover, I
explore the impact of including machine learning techniques in the post-processing
stage of the gravitational-wave search algorithm, “X-Pypeline”. When performing
a two detector network search for a gravitational wave from a Galactic supernova,
this thesis finds that including information about glitch families and using machine
learning techniques in the post-processing stages of the analysis can improve the
sensitive range of the search by 10-15 percent over the standard post-processing
method
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