41 research outputs found
Directed searches for continuous gravitational waves from binary systems: parameter-space metrics and optimal Scorpius X-1 sensitivity
We derive simple analytic expressions for the (coherent and semi-coherent)
phase metrics of continuous-wave sources in low-eccentricity binary systems,
both for the long-segment and short- segment regimes (compared to the orbital
period). The resulting expressions correct and extend previous results found in
the literature. We present results of extensive Monte-Carlo studies comparing
metric mismatch predictions against the measured loss of detection statistic
for binary parameter offsets. The agreement is generally found to be within ~
10%-30%. As an application of the metric template expressions, we estimate the
optimal achievable sensitivity of an Einstein@Home directed search for Scorpius
X-1, under the assumption of sufficiently small spin wandering. We find that
such a search, using data from the upcoming advanced detectors, would be able
to beat the torque- balance level [1,2] up to a frequency of ~ 500 - 600 Hz, if
orbital eccentricity is well-constrained, and up to a frequency of ~ 160 - 200
Hz for more conservative assumptions about the uncertainty on orbital
eccentricity.Comment: 25 pages, 8 figure
Fully coherent follow-up of continuous gravitational-wave candidates: an application to Einstein@Home results
We characterize and present the details of the follow-up method used on the
most significant outliers of the Hough Einstein@Home all-sky search for
continuous gravitational waves arXiv:1207.7176. This follow-up method is based
on the two-stage approach introduced in arXiv:1303.2471, consisting of a
semicoherent refinement followed by a fully coherent zoom. We quantify the
efficiency of the follow-up pipeline using simulated signals in Gaussian noise.
This pipeline does not search beyond first-order frequency spindown, and
therefore we also evaluate its robustness against second-order spindown. We
present the details of the Hough Einstein@Home follow-up (arXiv:1207.7176) on
three hardware-injected signals and on the 8 most significant outliers of
unknown origin.Comment: 8 pages, 3 figures, 3 table
Novel directed search strategy to detect continuous gravitational waves from neutron stars in low- and high-eccentricity binary systems
We describe a novel, very fast and robust, directed search incoherent method
for periodic gravitational waves (GWs) from neutron stars in binary systems. As
directed search, we assume the source sky position to be known with enough
accuracy, but all other parameters are supposed to be unknown. We exploit the
frequency-modulation due to source orbital motion to unveil the signal
signature by commencing from a collection of time and frequency peaks. We
validate our pipeline adding 131 artificial continuous GW signals from pulsars
in binary systems to simulated detector Gaussian noise, characterized by a
power spectral density Sh = 4x10^-24 Hz^-1/2 in the frequency interval [70,
200] Hz, which is overall commensurate with the advanced detector design
sensitivities. The pipeline detected 128 signals, and the weakest signal
injected and detected has a GW strain amplitude of ~10^-24, assuming one month
of gapless data collected by a single advanced detector. We also provide
sensitivity estimations, which show that, for a single- detector data covering
one month of observation time, depending on the source orbital Doppler
modulation, we can detect signals with an amplitude of ~7x10^-25. By using
three detectors, and one year of data, we would easily gain more than a factor
3 in sensitivity, translating into being able to detect weaker signals. We also
discuss the parameter estimate proficiency of our method, as well as
computational budget, which is extremely cheap. In fact, sifting one month of
single-detector data and 131 Hz-wide frequency range takes roughly 2.4 CPU
hours. Due to the high computational speed, the current procedure can be
readily applied in ally-sky schemes, sieving in parallel as many sky positions
as permitted by the available computational power
Principles of wide bandwidth acoustic detectors and the single-mass DUAL detector
We apply the standard theory of the elastic body to obtain a set of equations
describing the behavior of an acoustic Gravitational Wave detector, fully
taking into account the 3-dimensional properties of the mass, the readout and
the signal. We show that the advantages given by a Dual detector made by two
nested oscillators can also be obtained by monitoring two different acoustic
modes of the same oscillator, thus easing the detector realization. We apply
these concepts and by means of an optimization process we derive the main
figures of such a single-mass Dual detector designed specifically for the
frequency interval 2-5kHz. Finally we calculate the SQL sensitivity of this
detector.Comment: 29 pages, 10 figure
A method to search for long duration gravitational wave transients from isolated neutron stars using the generalized FrequencyHough
We describe a method to detect gravitational waves lasting
emitted by young, isolated neutron stars, such as those that could form after a
supernova or a binary neutron star merger, using advanced LIGO/Virgo data. The
method is based on a generalization of the FrequencyHough (FH), a pipeline that
performs hierarchical searches for continuous gravitational waves by mapping
points in the time/frequency plane of the detector to lines in the
frequency/spindown plane of the source. We show that signals whose spindowns
are related to their frequencies by a power law can be transformed to
coordinates where the behavior of these signals is always linear, and can
therefore be searched for by the FH. We estimate the sensitivity of our search
across different braking indices, and describe the portion of the parameter
space we could explore in a search using varying fast Fourier Transform (FFT)
lengths.Comment: 15 figure
Searching for continuous gravitational wave signals using LIGO and Virgo detectors
Direct and unequivocal detection of gravitational waves represents a great
challenge of contemporary physics and astrophysics. A worldwide effort is
currently operating towards this direction, building ever sensitive detectors,
improving the modelling of gravitational wave sources and employing ever more
sophisticated and powerful data analysis techniques. In this paper we review
the current status of LIGO and Virgo ground based interferometric detectors and
some data analysis tools used in the continuous wave searches to extract the
faint gravitational signals from the interferometric noise data. Moreover we
discuss also relevant results from recent continuous wave searches.Comment: 9 pages, 1 figure, http://www.fisica.unisalento.it/iwra/index2.ph
OctApps:a library of Octave functions for continuous gravitational-wave data analysis
Gravitational waves are minute ripples in spacetime, first predicted by Einstein's general theory of relativity in 1916. Gravitational waves from rapidly-rotating neutron stars, whose shape deviates from perfect axisymmetry, are a potential astrophysical source of gravitational waves, but which so far have not been detected. The search for this type of signals, also known as continuous waves, presents a significant data analysis challenge, as their weak signatures are expected to be buried deep within the instrumental noise of the LIGO and Virgo detectors. The OctApps library provides various functions, written in Octave, intended to aid research scientists who perform searches for continuous gravitational waves
Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)
This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands