816 research outputs found
Parameter-space metric of semicoherent searches for continuous gravitational waves
Continuous gravitational-wave (CW) signals such as emitted by spinning
neutron stars are an important target class for current detectors. However, the
enormous computational demand prohibits fully coherent broadband all-sky
searches for prior unknown CW sources over wide ranges of parameter space and
for yearlong observation times. More efficient hierarchical "semicoherent"
search strategies divide the data into segments much shorter than one year,
which are analyzed coherently; then detection statistics from different
segments are combined incoherently. To optimally perform the incoherent
combination, understanding of the underlying parameter-space structure is
requisite. This problem is addressed here by using new coordinates on the
parameter space, which yield the first analytical parameter-space metric for
the incoherent combination step. This semicoherent metric applies to broadband
all-sky surveys (also embedding directed searches at fixed sky position) for
isolated CW sources. Furthermore, the additional metric resolution attained
through the combination of segments is studied. From the search parameters (sky
position, frequency, and frequency derivatives), solely the metric resolution
in the frequency derivatives is found to significantly increase with the number
of segments.Comment: 14 pages, 5 figures (matching Phys.Rev.D version
A nonlinear detection algorithm for periodic signals in gravitational wave detectors
We present an algorithm for the detection of periodic sources of
gravitational waves with interferometric detectors that is based on a special
symmetry of the problem: the contributions to the phase modulation of the
signal from the earth rotation are exactly equal and opposite at any two
instants of time separated by half a sidereal day; the corresponding is true
for the contributions from the earth orbital motion for half a sidereal year,
assuming a circular orbit. The addition of phases through multiplications of
the shifted time series gives a demodulated signal; specific attention is given
to the reduction of noise mixing resulting from these multiplications. We
discuss the statistics of this algorithm for all-sky searches (which include a
parameterization of the source spin-down), in particular its optimal
sensitivity as a function of required computational power. Two specific
examples of all-sky searches (broad-band and narrow-band) are explored
numerically, and their performances are compared with the stack-slide technique
(P. R. Brady, T. Creighton, Phys. Rev. D, 61, 082001).Comment: 9 pages, 3 figures, to appear in Phys. Rev.
Data analysis of gravitational-wave signals from spinning neutron stars. IV. An all-sky search
We develop a set of data analysis tools for a realistic all-sky search for
continuous gravitational-wave signals. The methods that we present apply to
data from both the resonant bar detectors that are currently in operation and
the laser interferometric detectors that are in the final stages of
construction and commissioning. We show that with our techniques we shall be
able to perform an all-sky 2-day long coherent search of the narrow-band data
from the resonant bar EXPLORER with no loss of signals with the dimensionless
amplitude greater than .Comment: REVTeX, 26 pages, 1 figure, submitted to Phys. Rev.
Research notes: Soybean research and breeding in Poland
Soybean has been subjected to research and breeding in Poland for dozens of years . Despite development of native varieties, soybean has not yet been cultivated on a large scale. The evergrowing demand for commercial protein intensified interest in this plant
Matching of the continuous gravitational wave in an all sky search
We investigate the matching of continuous gravitational wave (CGW) signals in
an all sky search with reference to Earth based laser interferometric
detectors. We consider the source location as the parameters of the signal
manifold and templates corresponding to different source locations. It has been
found that the matching of signals from locations in the sky that differ in
their co-latitude and longitude by radians decreases with source
frequency. We have also made an analysis with the other parameters affecting
the symmetries. We observe that it may not be relevant to take care of the
symmetries in the sky locations for the search of CGW from the output of
LIGO-I, GEO600 and TAMA detectors.Comment: 16 pages, 7 figures, 3 Tables, To appear in Int. J. Mod. Phys.
Research Notes : Evaluation of soybean germplasm collection for climatic conditions in Poland
In 1974 studies were commenced to evaluate the variation in qualities and traits of soybean. The material covered a collection of 2412 entries including 275 varieties and 2137 genetic lines. The entries representing Maturity Groups (MGs) 00-IV were obtained from the following centers: U.S. Regional Soybean Lab., Urbana, Illinois, USA; Corn Breeding Lab . , Hokkaido, Japan; National Agric. Exp. Sta . , Hitsujigaoka, Sapporo, Japan; Weibullsholm Inst. Branch Sta., Fiskeby, Sweden; Dept. of Crop Science, Univ. of Guelph, Canada and Research Branch Canada Agric. Morden, Manitoba, Canada (41-58° northern latitude
Data analysis of gravitational-wave signals from spinning neutron stars. V. A narrow-band all-sky search
We present theory and algorithms to perform an all-sky coherent search for
periodic signals of gravitational waves in narrow-band data of a detector. Our
search is based on a statistic, commonly called the -statistic,
derived from the maximum-likelihood principle in Paper I of this series. We
briefly review the response of a ground-based detector to the
gravitational-wave signal from a rotating neuron star and the derivation of the
-statistic. We present several algorithms to calculate efficiently
this statistic. In particular our algorithms are such that one can take
advantage of the speed of fast Fourier transform (FFT) in calculation of the
-statistic. We construct a grid in the parameter space such that
the nodes of the grid coincide with the Fourier frequencies. We present
interpolation methods that approximately convert the two integrals in the
-statistic into Fourier transforms so that the FFT algorithm can
be applied in their evaluation. We have implemented our methods and algorithms
into computer codes and we present results of the Monte Carlo simulations
performed to test these codes.Comment: REVTeX, 20 pages, 8 figure
Gravitational Waves from Quasi-Circular Black Hole Binaries in Dynamical Chern-Simons Gravity
Dynamical Chern-Simons gravity cannot be strongly constrained with current
experiments because it reduces to General Relativity in the weak-field limit.
This theory, however, introduces modifications in the non-linear, dynamical
regime, and thus, it could be greatly constrained with gravitational waves from
the late inspiral of black hole binaries. We complete the first self-consistent
calculation of such gravitational waves in this theory. For favorable
spin-orientations, advanced ground-based detectors may improve existing
solar-system constraints by 6 orders of magnitude.Comment: 6 pages, 1 figure; errors corrected in Eqs. (8) and (9
On the determination of the last stable orbit for circular general relativistic binaries at the third post-Newtonian approximation
We discuss the analytical determination of the location of the Last Stable
Orbit (LSO) in circular general relativistic orbits of two point masses. We use
several different ``resummation methods'' (including new ones) based on the
consideration of gauge-invariant functions, and compare the results they give
at the third post-Newtonian (3PN) approximation of general relativity. Our
treatment is based on the 3PN Hamiltonian of Jaranowski and Sch\"afer. One of
the new methods we introduce is based on the consideration of the (invariant)
function linking the angular momentum and the angular frequency. We also
generalize the ``effective one-body'' approach of Buonanno and Damour by
introducing a non-minimal (i.e. ``non-geodesic'') effective dynamics at the 3PN
level. We find that the location of the LSO sensitively depends on the
(currently unknown) value of the dimensionless quantity \oms which
parametrizes a certain regularization ambiguity of the 3PN dynamics. We find,
however, that all the analytical methods we use numerically agree between
themselves if the value of this parameter is \oms\simeq-9. This suggests that
the correct value of \oms is near -9 (the precise value
\oms^*\equiv-{47/3}+{41/64}\pi^2=-9.3439... seems to play a special role). If
this is the case, we then show how to further improve the analytical
determination of various LSO quantities by using a ``Shanks'' transformation to
accelerate the convergence of the successive (already resummed) PN estimates.Comment: REVTeX, 25 pages, 3 figures, submitted to Phys. Rev.
Gravitational waves from inspiralling compact binaries with magnetic dipole moments
We investigate the effects of the magnetic dipole-dipole coupling and the
electromagnetic radiation on the frequency evolution of gravitational waves
from inspiralling binary neutron stars with magnetic dipole moments. This study
is motivated by the discovery of the superstrongly magnetized neutron stars,
i.e., magnetar. We derive the contributions of the magnetic fields to the
accumulated cycles in gravitational waves as , where denotes the strength of the polar magnetic
fields of each neutron star in the binary system. It is found that the effects
of the magnetic fields will be negligible for the detection and the parameter
estimation of gravitational waves, if the upper limit for magnetic fields of
neutron stars are less than G, which is the maximum magnetic
field observed in the soft gamma repeaters and the anomalous X-ray pulsars up
to date. We also discuss the implications of electromagnetic radiation from the
inspiralling binary neutron stars for the precursory X-ray emission prior to
the gamma ray burst observed by the Ginga satellite.Comment: 15 pages, no figures, accepted for publication in Ap
- …