22 research outputs found
Enabling high confidence detections of gravitational-wave bursts
With the advanced LIGO and Virgo detectors taking observations the detection
of gravitational waves is expected within the next few years. Extracting
astrophysical information from gravitational wave detections is a well-posed
problem and thoroughly studied when detailed models for the waveforms are
available. However, one motivation for the field of gravitational wave
astronomy is the potential for new discoveries. Recognizing and characterizing
unanticipated signals requires data analysis techniques which do not depend on
theoretical predictions for the gravitational waveform. Past searches for
short-duration un-modeled gravitational wave signals have been hampered by
transient noise artifacts, or "glitches," in the detectors. In some cases, even
high signal-to-noise simulated astrophysical signals have proven difficult to
distinguish from glitches, so that essentially any plausible signal could be
detected with at most 2-3 level confidence. We have put forth the
BayesWave algorithm to differentiate between generic gravitational wave
transients and glitches, and to provide robust waveform reconstruction and
characterization of the astrophysical signals. Here we study BayesWave's
capabilities for rejecting glitches while assigning high confidence to
detection candidates through analytic approximations to the Bayesian evidence.
Analytic results are tested with numerical experiments by adding simulated
gravitational wave transient signals to LIGO data collected between 2009 and
2010 and found to be in good agreement.Comment: 15 pages, 6 figures, submitted to PR
Enabling high confidence detections of gravitational-wave bursts
Extracting astrophysical information from gravitational-wave detections is a well-posed problem and thoroughly studied when detailed models for the waveforms are available. However, one motivation for the field of gravitational-wave astronomy is the potential for new discoveries. Recognizing and characterizing unanticipated signals requires data analysis techniques which do not depend on theoretical predictions for the gravitational waveform. Past searches for short-duration unmodeled gravitational-wave signals have been hampered by transient noise artifacts, or “glitches,” in the detectors. We have put forth the BayesWave algorithm to differentiate between generic gravitational-wave transients and glitches, and to provide robust waveform reconstruction and characterization of the astrophysical signals. Here we study BayesWave’s capabilities for rejecting glitches while assigning high confidence to detection candidates through analytic approximations to the Bayesian evidence. Analytic results are tested with numerical experiments by adding simulated gravitational-wave transient signals to LIGO data collected between 2009 and 2010 and found to be in good agreement
Leveraging waveform complexity for confident detection of gravitational waves
The recent completion of Advanced LIGO suggests that gravitational waves may soon be directly observed. Past searches for gravitational-wave transients have been impacted by transient noise artifacts, known as glitches, introduced into LIGO data due to instrumental and environmental effects. In this work, we explore how waveform complexity, instead of signal-to-noise ratio, can be used to rank event candidates and distinguish short duration astrophysical signals from glitches. We test this framework using a new hierarchical pipeline that directly compares the Bayesian evidence of explicit signal and glitch models. The hierarchical pipeline is shown to perform well and, in particular, to allow high-confidence detections of a range of waveforms at a realistic signal-to-noise ratio with a two-detector network
Multi-messenger astronomy of gravitational-wave sources with flexible wide-area radio transient surveys
We explore opportunities for multi-messenger astronomy using gravitational
waves (GWs) and prompt, transient low-frequency radio emission to study highly
energetic astrophysical events. We review the literature on possible sources of
correlated emission of gravitational waves and radio transients, highlighting
proposed mechanisms that lead to a short-duration, high-flux radio pulse
originating from the merger of two neutron stars or from a superconducting
cosmic string cusp. We discuss the detection prospects for each of these
mechanisms by low-frequency dipole array instruments such as LWA1, LOFAR and
MWA. We find that a broad range of models may be tested by searching for radio
pulses that, when de-dispersed, are temporally and spatially coincident with a
LIGO/Virgo GW trigger within a \usim 30 second time window and \usim 200
\mendash 500 \punits{deg}^{2} sky region. We consider various possible
observing strategies and discuss their advantages and disadvantages. Uniquely,
for low-frequency radio arrays, dispersion can delay the radio pulse until
after low-latency GW data analysis has identified and reported an event
candidate, enabling a \emph{prompt} radio signal to be captured by a
deliberately targeted beam. If neutron star mergers do have detectable prompt
radio emissions, a coincident search with the GW detector network and
low-frequency radio arrays could increase the LIGO/Virgo effective search
volume by up to a factor of \usim 2. For some models, we also map the
parameter space that may be constrained by non-detections.Comment: 31 pages, 4 figure
Observations of Giant Pulses from Pulsar PSR B0950+08 using LWA1
We report the detection of giant pulse emission from PSR B0950+08 in 24 hours
of observations made at 39.4 MHz, with a bandwidth of 16 MHz, using the first
station of the Long Wavelength Array, LWA1. We detected 119 giant pulses from
PSR B0950+08 (at its dispersion measure), which we define as having SNRs at
least 10 times larger than for the mean pulse in our data set. These 119 pulses
are 0.035% of the total number of pulse periods in the 24 hours of
observations. The rate of giant pulses is about 5.0 per hour. The cumulative
distribution of pulse strength is a steep power law, , but much less steep than would be expected if we were observing the
tail of a Gaussian distribution of normal pulses. We detected no other
transient pulses in a dispersion measure range from 1 to 90 pc cm, in
the beam tracking PSR B0950+08. The giant pulses have a narrower temporal width
than the mean pulse (17.8 ms, on average, vs. 30.5 ms). The pulse widths are
consistent with a previously observed weak dependence on observing frequency,
which may be indicative of a deviation from a Kolmogorov spectrum of electron
density irregularities along the line of sight. The rate and strength of these
giant pulses is less than has been observed at 100 MHz. Additionally, the
mean (normal) pulse flux density we observed is less than at 100 MHz.
These results suggest this pulsar is weaker and produces less frequent giant
pulses at 39 MHz than at 100 MHz.Comment: 27 pages, 12 figures, typos correcte
Mitigation of the instrumental noise transient in gravitational-wave data surrounding GW170817
In the coming years gravitational-wave detectors will undergo a series of
improvements, with an increase in their detection rate by about an order of
magnitude. Routine detections of gravitational-wave signals promote novel
astrophysical and fundamental theory studies, while simultaneously leading to
an increase in the number of detections temporally overlapping with
instrumentally- or environmentally-induced transients in the detectors
(glitches), often of unknown origin. Indeed, this was the case for the very
first detection by the LIGO and Virgo detectors of a gravitational-wave signal
consistent with a binary neutron star coalescence, GW170817. A loud glitch in
the LIGO-Livingston detector, about one second before the merger, hampered
coincident detection (which was initially achieved solely with LIGO-Hanford
data). Moreover, accurate source characterization depends on specific
assumptions about the behavior of the detector noise that are rendered invalid
by the presence of glitches. In this paper, we present the various techniques
employed for the initial mitigation of the glitch to perform source
characterization of GW170817 and study advantages and disadvantages of each
mitigation method. We show that, despite the presence of instrumental noise
transients louder than the one affecting GW170817, we are still able to produce
unbiased measurements of the intrinsic parameters from simulated injections
with properties similar to GW170817.Comment: 11 pages, 3 figures, accepted in PR
LOOC UP: Locating and observing optical counterparts to gravitational wave bursts
Gravitational wave (GW) bursts (short duration signals) are expected to be
associated with highly energetic astrophysical processes. With such high
energies present, it is likely these astrophysical events will have signatures
in the EM spectrum as well as in gravitational radiation. We have initiated a
program, "Locating and Observing Optical Counterparts to Unmodeled Pulses in
Gravitational Waves" (LOOC UP) to promptly search for counterparts to GW burst
candidates. The proposed method analyzes near real-time data from the
LIGO-Virgo network, and then uses a telescope network to seek optical-transient
counterparts to candidate GW signals. We carried out a pilot study using
S5/VSR1 data from the LIGO-Virgo network to develop methods and software tools
for such a search. We will present the method, with an emphasis on the
potential for such a search to be carried out during the next science run of
LIGO and Virgo, expected to begin in 2009.Comment: 11 pages, 2 figures; v2) added acknowledgments, additional
references, and minor text changes v3) added 1 figure, additional references,
and minor text changes. v4) Updated references and acknowledgments. To be
published in the GWDAW 12 Conf. Proc. by Classical and Quantum Gravit
Observations of Giant Pulses from Pulsar B0950+08 Using LWA1
We report the detection of giant pulse (GP) emission from PSR B0950+08 in 24 hours of observations made at 39.4 MHz, with a bandwidth of 16 MHz, using the first station of the Long Wavelength Array. We detected 119 GPs from PSR B0950+08 (at its dispersion measure (DM)), which we define as having a signal-to-noise ratio at least 10 times larger than for the mean pulse in our data set. These 119 pulses are 0.035% of the total number of pulse periods in the 24 hours of observations. The rate of GPs is about 5.0 per hour. The cumulative distribution of pulse strength S is a steep power law, _N(>S) ∝ S^(-4.7), but much less steep than would be expected if we were observing the tail of a Gaussian distribution of normal pulses. We detected no other transient pulses in a DM range from 1 to 90 pc cm^(−3), in the beam tracking PSR B0950+08. The GPs have a narrower temporal width than the mean pulse (17.8 ms, on average, versus 30.5 ms). The pulse widths are consistent with a previously observed weak dependence on observing frequency, which may be indicative of a deviation from a Kolmogorov spectrum of electron density irregularities along the line of sight. The rate and strength of these GPs is less than has been observed at ~100 MHz. Additionally, the mean (normal) pulse flux density we observed is less than at ~100 MHz. These results suggest this pulsar is weaker and produces less frequent GPs at 39 MHz than at 100 MHz