964 research outputs found
Higher-order spin effects in the amplitude and phase of gravitational waveforms emitted by inspiraling compact binaries: Ready-to-use gravitational waveforms
We provide ready-to-use time-domain gravitational waveforms for spinning
compact binaries with precession effects through 1.5PN order in amplitude and
compute their mode decomposition using spin-weighted -2 spherical harmonics. In
the presence of precession, the gravitational-wave modes (l,m) contain
harmonics originating from combinations of the orbital frequency and precession
frequencies. We find that the gravitational radiation from binary systems with
large mass asymmetry and large inclination angle can be distributed among
several modes. For example, during the last stages of inspiral, for some
maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes
can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not
too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude
smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing
compact binaries, we apply the stationary-phase approximation and derive the
frequency-domain gravitational waveforms including spin-orbit and spin(1)-
spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and
2.5PN order in phase. Since spin effects in the amplitude through 2PN order
affect only the first and second harmonics of the orbital phase, they do not
extend the mass reach of gravitational-wave detectors. However, they can
interfere with other harmonics and lower or raise the signal-to-noise ratio
depending on the spin orientation. These ready-to-use waveforms could be
employed in the data-analysis of the spinning, inspiraling binaries as well as
in comparison studies at the interface between analytical and numerical
relativity.Comment: 43 pages, 10 Postscript figures. submitted to Physical Review D.
Includes corrections due to errat
Parameter estimation of coalescing supermassive black hole binaries with LISA
Laser Interferometer Space Antenna (LISA) will routinely observe coalescences
of supermassive black hole (BH) binaries up to very high redshifts. LISA can
measure mass parameters of such coalescences to a relative accuracy of
, for sources at a distance of 3 Gpc. The problem of parameter
estimation of massive nonspinning binary black holes using post-Newtonian (PN)
phasing formula is studied in the context of LISA. Specifically, the
performance of the 3.5PN templates is contrasted against its 2PN counterpart
using a waveform which is averaged over the LISA pattern functions. The
improvement due to the higher order corrections to the phasing formula is
examined by calculating the errors in the estimation of mass parameters at each
order. The estimation of the mass parameters and are
significantly enhanced by using the 3.5PN waveform instead of the 2PN one. For
an equal mass binary of at a luminosity distance of 3 Gpc,
the improvement in chirp mass is and that of is .
Estimation of coalescence time worsens by 43%. The improvement is larger
for the unequal mass binary mergers. These results are compared to the ones
obtained using a non-pattern averaged waveform. The errors depend very much on
the location and orientation of the source and general conclusions cannot be
drawn without performing Monte Carlo simulations. Finally the effect of the
choice of the lower frequency cut-off for LISA on the parameter estimation is
studied.Comment: 12 pages, 5 figures (eps) significant revision, accepted for
publication in Phys. Rev. D. Matches with the published versio
Using generalized PowerFlux methods to estimate the parameters of periodic gravitational waves
We investigate methods to estimate the parameters of the gravitational-wave
signal from a spinning neutron star using Fourier transformed segments of the
strain response from an interferometric detector. Estimating the parameters
from the power, we find generalizations of the PowerFlux method. Using
simulated elliptically polarized signals injected into Gaussian noise, we apply
the generalized methods to estimate the squared amplitudes of the plus and
cross polarizations (and, in the most general case, the polarization angle),
and test the relative detection efficiencies of the various methods.Comment: 8 pages, presented at Amalid7, Sydney, Australia (July 2007), fixed
minor typos and clarified discussion to match published CQG version; updated
reference
Binary black hole detection rates in inspiral gravitational wave searches
The signal-to-noise ratios (SNRs) for quasi-circular binary black hole
inspirals computed from restricted post-Newtonian waveforms are compared with
those attained by more complete post-Newtonian signals, which are
superpositions of amplitude-corrected harmonics of the orbital phase. It is
shown that if one were to use the best available amplitude-corrected waveforms
for detection templates, one should expect SNRs in actual searches to be
significantly lower than those suggested by simulations based purely on
restricted waveforms.Comment: 9 pages, 1 figur
Infinite Kinematic Self-Similarity and Perfect Fluid Spacetimes
Perfect fluid spacetimes admitting a kinematic self-similarity of infinite
type are investigated. In the case of plane, spherically or hyperbolically
symmetric space-times the field equations reduce to a system of autonomous
ordinary differential equations. The qualitative properties of solutions of
this system of equations, and in particular their asymptotic behavior, are
studied. Special cases, including some of the invariant sets and the geodesic
case, are examined in detail and the exact solutions are provided. The class of
solutions exhibiting physical self-similarity are found to play an important
role in describing the asymptotic behavior of the infinite kinematic
self-similar models.Comment: 38 pages, 6 figures. Accepted for publication in General Relativity &
Gravitatio
Self-similar static solutions admitting a two-space of constant curvature
A recent result by Haggag and Hajj-Boutros is reviewed within the framework
of self-similar space-times, extending, in some sense, their results and
presenting a family of metrics consisting of all the static spherically
symmetric perfect fluid solutions admitting a homothety.Comment: 6 page
Large-scale distribution of microbial and viral populations in the South Atlantic Ocean
Viruses are abundant, diverse and dynamic compo-nents of the marine environments and play a signi?-cant role in the ocean biogeochemical cycles. Toassess potential variations in the relation betweenviruses and microbes in different geographic regionsand depths, viral and microbial abundance and pro-duction were determined throughout the watercolumn along a latitudinal transect in the South Atlan-tic Ocean. Path analysis was used to examine therelationships between several abiotic and bioticparameters and the different microbial and viral popu-lations distinguished by ?ow cytometry.The depth-integrated contribution of microbial andviral abundance to the total microbial and viralbiomass differed signi?cantly among the differentprovinces. Additionally, the virus-to-microbe ratioincreased with depth and decreased laterally towardsthe more productive regions. Our data revealed thatthe abundance of phytoplankton and microbes is themain controlling factor of the viral populations in theeuphotic and mesopelagic layers, whereas in thebathypelagic realm, viral abundance was only weaklyrelated to the biotic and abiotic variables. The relativecontribution of the three viral populations distin-guished by ?ow cytometry showed a clear geographi-cal pattern throughout the water column, suggestingthat these populations are composed of distinct tax
Parameter estimation of compact binaries using the inspiral and ringdown waveforms
We analyze the problem of parameter estimation for compact binary systems
that could be detected by ground-based gravitational wave detectors.
So far this problem has only been dealt with for the inspiral and the
ringdown phases separately. In this paper, we combine the information from both
signals, and we study the improvement in parameter estimation, at a fixed
signal-to-noise ratio, by including the ringdown signal without making any
assumption on the merger phase. The study is performed for both initial and
advanced LIGO and VIRGO detectors.Comment: matching cqg versio
Removing non-stationary, non-harmonic external interference from gravitational wave interferometer data
We describe a procedure to identify and remove a class of non-stationary and
non-harmonic interference lines from gravitational wave interferometer data.
These lines appear to be associated with the external electricity main
supply, but their amplitudes are non-stationary and they do not appear at
harmonics of the fundamental supply frequency. We find an empirical model able
to represent coherently all the non-harmonic lines we have found in the power
spectrum, in terms of an assumed reference signal of the primary supply input
signal. If this signal is not available then it can be reconstructed from the
same data by making use of the coherent line removal algorithm that we have
described elsewhere. All these lines are broadened by frequency changes of the
supply signal, and they corrupt significant frequency ranges of the power
spectrum. The physical process that generates this interference is so far
unknown, but it is highly non-linear and non-stationary. Using our model, we
cancel the interference in the time domain by an adaptive procedure that should
work regardless of the source of the primary interference. We have applied the
method to laser interferometer data from the Glasgow prototype detector, where
all the features we describe in this paper were observed. The algorithm has
been tuned in such a way that the entire series of wide lines corresponding to
the electrical interference are removed, leaving the spectrum clean enough to
detect signals previously masked by them. Single-line signals buried in the
interference can be recovered with at least 75 % of their original signal
amplitude.Comment: 14 pages, 5 figures, Revtex, psfi
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