629 research outputs found
A new data analysis framework for the search of continuous gravitational wave signals
Continuous gravitational wave signals, like those expected by asymmetric
spinning neutron stars, are among the most promising targets for LIGO and Virgo
detectors. The development of fast and robust data analysis methods is crucial
to increase the chances of a detection. We have developed a new and flexible
general data analysis framework for the search of this kind of signals, which
allows to reduce the computational cost of the analysis by about two orders of
magnitude with respect to current procedures. This can correspond, at fixed
computing cost, to a sensitivity gain of up to 10%-20%, depending on the search
parameter space. Some possible applications are discussed, with a particular
focus on a directed search for sources in the Galactic center. Validation
through the injection of artificial signals in the data of Advanced LIGO first
observational science run is also shown.Comment: 21 pages, 8 figure
Prospects of continuous gravitational waves from Fermi LAT sources
Non-axisymmetric spinning Neutron Stars are expected to be sources of continuous gravitational waves. Only a small fraction of the total number of neutron stars believed to exist in the Galaxy is observed through their electromagnetic emission. This number steadily increasing recently, thanks to the Fermi Large Area Telescope and to radio surveys. The Fermi Large Area Telescope catalogue contains several potentially interesting sources for gravitational-wave searches, such as supernova remnants and the “unassociated” sources. In order to look for continuous gravitational signals the knowledge of the NS parameters, i.e. rotational frequency and position, is needed. Depending on the degree of accuracy with which these parameters are known, several types of searches can be performed. In this paper I will discuss the perspectives and considerations of continuous gravitational-wave searches for Fermi LAT sources
An improved algorithm for narrow-band searches of continuous gravitational waves
Continuous gravitational waves signals, emitted by asymmetric spinning
neutron stars, are among the main targets of current detectors like Advanced
LIGO and Virgo. In the case of sources, like pulsars, which rotational
parameters are measured through electromagnetic observations, typical searches
assume that the gravitational wave frequency is at a given known fixed ratio
with respect to the star rotational frequency. For instance, for a neutron star
rotating around one of its principal axis of inertia the gravitational signal
frequency would be exactly two times the rotational frequency of the star. It
is possible, however, that this assumption is wrong. This is why search
algorithms able to take into account a possible small mismatch between the
gravitational waves frequency and the frequency inferred from electromagnetic
observations have been developed. In this paper we present an improved pipeline
to perform such narrow-band searches for continuous gravitational waves from
neutron stars, about three orders of magnitude faster than previous
implementations. The algorithm that we have developed is based on the {\it
5-vectors} framework and is able to perform a fully coherent search over a
frequency band of width (Hertz) and for hundreds of spin-down
values running a few hours on a standard workstation. This new algorithm opens
the possibility of long coherence time searches for objects which rotational
parameters are highly uncertain.Comment: 19 pages, 8 figures, 6 tables, submitted to CQ
A semi-coherent analysis method to search for continuous gravitational waves emitted by ultra-light boson clouds around spinning black holes
As a consequence of superradiant instability induced in Kerr black holes,
ultra-light boson clouds can be a source of persistent gravitational waves,
potentially detectable by current and future gravitational-wave detectors.
These signals have been predicted to be nearly monochromatic, with a small
steady frequency increase (spin-up), but given the several assumptions and
simplifications done at theoretical level, it is wise to consider, from the
data analysis point of view, a broader class of gravitational signals in which
the phase (or the frequency) slightly wander in time. Also other types of
sources, e.g. neutron stars in which a torque balance equilibrium exists
between matter accretion and emission of persistent gravitational waves, would
fit in this category. In this paper we present a robust and computationally
cheap analysis pipeline devoted to the search of such kind of signals. We
provide a full characterization of the method, through both a theoretical
sensitivity estimation and through the analysis of syntethic data in which
simulated signals have been injected. The search setup for both all-sky
searches and higher sensitivity directed searches is discussed.Comment: 13 pages, 13 figure
Combining chirp mass, luminosity distance and sky localisation from gravitational wave events to detect the cosmic dipole
A key test of the isotropy of the Universe on large scales consists in
comparing the dipole in the Cosmic Microwave Background (CMB) temperature with
the dipole in the distribution of sources at low redshift. Current analyses
find a dipole in the number counts of quasars and radio sources that is 2-5
times larger than expected from the CMB, leading to a tension reaching
5. In this paper, we derive a consistent framework to measure the
dipole independently from gravitational wave (GW) detections. We exploit the
fact that the observer velocity does not only change the distribution of events
in the sky, but also the luminosity distance and redshifted chirp mass, that
can be extracted from the GW waveform. We show that the estimator with higher
signal-to-noise ratio is the dipole in the chirp mass measured from a
population of binary neutron stars. Combining all estimators (accounting for
their covariance) improves the detectability of the dipole by 30-50 percent
compared to number counting of binary black holes alone. We find that a few
events are necessary to detect a dipole consistent with the CMB one,
whereas if the dipole is as large as predicted by radio sources, it will
already be detectable with events, which would correspond to a single
year of observation with next generation GW detectors. GW sources provide
therefore a robust and independent way of testing the isotropy of the Universe.Comment: 17 pages, 11 figues, submitted to MNRA
A 2D laser rangefinder scans dataset of standard EUR pallets
open5siopenIhab Mohamed, Alessio Capitanelli, Fulvio Mastrogiovanni, Stefano Rovetta, Renato ZaccariaMohamed, Ihab; Capitanelli, Alessio; Mastrogiovanni, Fulvio; Rovetta, Stefano; Zaccaria, RENATO UGO RAFFAEL
Aberration of gravitational waveforms by peculiar velocity
One key prediction of General Relativity is that gravitational waves areemitted with a pure spin-2 polarisation. Any extra polarisation mode, spin-1 orspin-0, is consequently considered a smoking gun for deviations from GeneralRelativity. In this paper, we show that the velocity of merging binaries withrespect to the observer gives rise to spin-1 polarisation in the observer frameeven in the context of General Relativity. These are pure projection effects,proportional to the plus and cross polarisations in the source frame, hencethey do not correspond to new degrees of freedom. We demonstrate that thespin-1 modes can always be rewritten as pure spin-2 modes coming from anaberrated direction. Since gravitational waves are not isotropically emittedaround binary systems, this aberration modifies the apparent orientation of thebinary system with respect to the observer: the system appears slightly rotateddue to the source velocity. Fortunately, this bias does not propagate to otherparameters of the system (and therefore does not spoil tests of GeneralRelativity), since the impact of the velocity can be fully reabsorbed into neworientation angles.<br
A morphology-independent search for gravitational wave echoes in data from the first and second observing runs of Advanced LIGO and Advanced Virgo
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