2,831 research outputs found
Upper limits on gravitational-wave signals based on loudest events
Searches for gravitational-wave bursts have often focused on the loudest
event(s) in searching for detections and in determining upper limits on
astrophysical populations. Typical upper limits have been reported on event
rates and event amplitudes which can then be translated into constraints on
astrophysical populations. We describe the mathematical construction of such
upper limits.Comment: 8 pages, 1 figur
FINDCHIRP: an algorithm for detection of gravitational waves from inspiraling compact binaries
Matched-filter searches for gravitational waves from coalescing compact
binaries by the LIGO Scientific Collaboration use the FINDCHIRP algorithm: an
implementation of the optimal filter with innovations to account for unknown
signal parameters and to improve performance on detector data that has
nonstationary and non-Gaussian artifacts. We provide details on the FINDCHIRP
algorithm as used in the search for subsolar mass binaries, binary neutron
stars, neutron star-black hole binaries, and binary black holes.Comment: 19 pages, 1 figure, journal version with Creative Commons 4.0
open-access license adde
A power filter for the detection of burst sources of gravitational radiation in interferometric detectors
We present a filter for detecting gravitational wave signals from burst
sources. This filter requires only minimal advance knowledge of the expected
signal: i.e. the signal's frequency band and time duration. It consists of a
threshold on the total power in the data stream in the specified signal band
during the specified time. This filter is optimal (in the Neyman-Pearson sense)
for signal searches where only this minimal information is available.Comment: 3 pages, RevTeX, GWDAW '99 proceedings contribution, submitted to
Int. J. Modern Phys.
Tumbleweeds and airborne gravitational noise sources for LIGO
Gravitational-wave detectors are sensitive not only to astrophysical
gravitational waves, but also to the fluctuating Newtonian gravitational forces
of moving masses in the ground and air around the detector. This paper studies
the gravitational effects of density perturbations in the atmosphere, and from
massive airborne objects near the detector. These effects were previously
considered by Saulson; in this paper I revisit these phenomena, considering
transient atmospheric shocks, and the effects of sound waves or objects
colliding with the ground or buildings around the test masses. I also consider
temperature perturbations advected past the detector as a source of
gravitational noise. I find that the gravitational noise background is below
the expected noise floor even of advanced interferometric detectors, although
only by an order of magnitude for temperature perturbations carried along
turbulent streamlines. I also find that transient shockwaves in the atmosphere
could potentially produce large spurious signals, with signal-to-noise ratios
in the hundreds in an advanced interferometric detector. These signals could be
vetoed by means of acoustic sensors outside of the buildings. Massive
wind-borne objects such as tumbleweeds could also produce gravitational signals
with signal-to-noise ratios in the hundreds if they collide with the
interferometer buildings, so it may be necessary to build fences preventing
such objects from approaching within about 30m of the test masses.Comment: 15 pages, 10 PostScript figures, uses REVTeX4.cls and epsfig.st
The Spartan 1 mission
The first Spartan mission is documented. The Spartan program, an outgrowth of a joint Naval Research Laboratory (NRL)/National Aeronautics and Space Administration (NASA)-Goddard Space Flight Center (GSFC) development effort, was instituted by NASA for launching autonomous, recoverable payloads from the space shuttle. These payloads have a precise pointing system and are intended to support a wide range of space-science observations and experiments. The first Spartan, carrying an NRL X-ray astronomy instrument, was launched by the orbiter Discovery (STS51G) on June 20, 1985 and recovered successfully 45 h later, on June 22. During this period, Spartan 1 conducted a preprogrammed series of observations of two X-ray sources: the Perseus cluster of galaxies and the center of our galaxy. The mission was successful from both on engineering and a scientific viewpoint. Only one problem was encountered, the attitude control system (ACS) shut down earlier than planned because of high attitude control system gas consumption. A preplanned emergency mode then placed Spartan 1 into a stable, safe condition and allowed a safe recovery. The events are described of the mission and presents X-ray maps of the two observed sources, which were produced from the flight data
Duality of Quasilocal Black Hole Thermodynamics
We consider T-duality of the quasilocal black hole thermodynamics for the
three-dimensional low energy effective string theory. Quasilocal thermodynamic
variables in the first law are explicitly calculated on a general axisymmetric
three-dimensional black hole solution and corresponding dual one. Physical
meaning of the dual invariance of the black hole entropy is considered in terms
of the Euclidean path integral formulation.Comment: 19 pages, Latex, no figures, to be published in Class. Quantum Grav.
Some minor changes, references adde
Moduli, Scalar Charges, and the First Law of Black Hole Thermodynamics
We show that under variation of moduli fields the first law of black
hole thermodynamics becomes , where are the scalar charges. We also show
that the ADM mass is extremized at fixed , , when the moduli
fields take the fixed value which depend only on electric
and magnetic charges. It follows that the least mass of any black hole with
fixed conserved electric and magnetic charges is given by the mass of the
double-extreme black hole with these charges. Our work allows us to interpret
the previously established result that for all extreme black holes the moduli
fields at the horizon take a value depending only
on the electric and magnetic conserved charges: is such
that the scalar charges .Comment: 3 pages, no figures, more detailed versio
Response of the Brazilian gravitational wave detector to signals from a black hole ringdown
It is assumed that a black hole can be disturbed in such a way that a
ringdown gravitational wave would be generated. This ringdown waveform is well
understood and is modelled as an exponentially damped sinusoid. In this work we
use this kind of waveform to study the performance of the SCHENBERG
gravitational wave detector. This first realistic simulation will help us to
develop strategies for the signal analysis of this Brazilian detector. We
calculated the signal-to-noise ratio as a function of frequency for the
simulated signals and obtained results that show that SCHENBERG is expected to
be sensitive enough to detect this kind of signal up to a distance of .Comment: 5 pages, 4 figures, Amaldi 5 Conference Proceedings contribution.
Submitted to Class. Quantum Gra
Finite size effects on thermal denaturation of globular proteins
Finite size effects on the cooperative thermal denaturation of proteins are
considered. A dimensionless measure of cooperativity, Omega, scales as N^zeta,
where N is the number of amino acids. Surprisingly, we find that zeta is
universal with zeta = 1 + gamma, where the exponent gamma characterizes the
divergence of the susceptibility for a self-avoiding walk. Our lattice model
simulations and experimental data are consistent with the theory. Our finding
rationalizes the marginal stability of proteins and substantiates the earlier
predictions that the efficient folding of two-state proteins requires the
folding transition temperature to be close to the collapse temperature.Comment: 3 figures. Physical Review Letters (in press
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