2,803 research outputs found
Advanced LIGO's ability to detect apparent violations of the cosmic censorship conjecture and the no-hair theorem through compact binary coalescence detections
We study the ability of the advanced Laser Interferometer Gravitational-wave
Observatory (aLIGO) to detect apparent violations of the cosmic censorship
conjecture and the no-hair theorem. The cosmic censorship conjecture, which is
believed to be true in the theory of general relativity, limits the
spin-to-mass-squared ratio of a Kerr black hole. The no-hair theorem, which is
also believed to be true in the theory of general relativity, suggests a
particular value for the tidal Love number of a non-rotating black hole. Using
the Fisher matrix formalism, we examine the measurability of the spin and tidal
deformability of compact binary systems involving at least one putative black
hole. Using parameter measurement errors and correlations obtained from the
Fisher matrix, we determine the smallest detectable violation of bounds implied
by the cosmic censorship conjecture and the no-hair theorem. We examine the
effect of excluding unphysical areas of parameter space when determining the
smallest detectable apparent violations, and we examine the effect of different
post-Newtonian corrections to the amplitude of the compact binary coalescence
gravitational waveform. In addition, we perform a brief study of how the
recently calculated 3.0 pN and 3.5 pN spin-orbit corrections to the phase
affect spin and mass parameter measurability. We find that physical priors on
the symmetric mass ratio and higher harmonics in the gravitational waveform
could significantly affect the ability of aLIGO to investigate cosmic
censorship and the no-hair theorem for certain systems.Comment: 21 pages, 7 figures, 6 table
Observational Limit on Gravitational Waves from Binary Neutron Stars in the Galaxy
Using optimal matched filtering, we search 25 hours of data from the LIGO 40-m prototype laser interferometric gravitational-wave detector for gravitational-wave chirps emitted by coalescing binary systems within our Galaxy. This is the first test of this filtering technique on real interferometric data. An upper limit on the rate R of neutron star binary inspirals in our Galaxy is obtained: with 90% confidence, R\u3c0.5hâ1. Similar experiments with LIGO interferometers will provide constraints on the population of tight binary neutron star systems in the Universe
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
Conserved masses in GHS Einstein and string black holes
We analyze the relationship between quasilocal masses calculated for
solutions of conformally related theories. We show that the ADM mass of a
static, spherically symmetric solution is conformally invariant (up to a
constant factor) only if the background action functional is conformally
invariant. Thus, the requirement of conformal invariance places restrictions on
the choice of reference spacetimes. We calculate the mass of the black hole
solutions obtained by Garfinkle, Horowitz, and Strominger (GHS) for both the
string and the Einstein metrics. In addition, the quasilocal thermodynamic
quantities in the string metrics are computed and discussed.Comment: 16 pages REVTeX with packages amsfonts and amssym
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
Star formation in the giant HII regions of M101
The molecular components of three giant HII regions (NGC 5461, NGC 5462, NGC
5471) in the galaxy M101 are investigated with new observations from the James
Clerk Maxwell Telescope, the NRAO 12-meter, and the Owens Valley millimeter
array. Of the three HII regions, only NGC 5461 had previously been detected in
CO emission.
We calculate preliminary values for the molecular mass of the GMCs in NGC
5461 by assuming a CO-to-H_2 factor (X factor) and then compare these values
with the virial masses. We conclude that the data in this paper demonstrate for
the first time that the value of X may decrease in regions with intense star
formation.
The molecular mass for the association of clouds in NGC 5461 is approximately
3x10^7 Mo and is accompanied by 1-2 times as much atomic mass. The observed CO
emission in NGC 5461 is an order of magnitude stronger than in NGC 5462, while
it was not possible to detect molecular gas toward NGC 5471 with the JCMT. An
even larger ratio of atomic to molecular gas in NGC 5471 was observed, which
might be attributed to efficient conversion of molecular to atomic gas.
The masses of the individual clouds in NGC 5461, which are gravitationally
bound, cover a range of (2-8) x 10^5 Mo, comparable with the masses of Galactic
giant molecular clouds (GMCs). Higher star forming efficiencies, and not
massive clouds, appear to be the prerequisite for the formation of the large
number of stars whose radiation is required to produce the giant HII regions in
M101.Comment: 32 pages, 5 figures, accepted for publication in the Astrophysical
Journa
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