CERES Collection:
https://dspace.lib.cranfield.ac.uk:443/handle/1826/13
20170424T17:06:50Z

Search of the Orion spur for continuous gravitational waves using a loosely coherent algorithm on data from LIGO interferometers
https://dspace.lib.cranfield.ac.uk:443/handle/1826/11790
Title: Search of the Orion spur for continuous gravitational waves using a loosely coherent algorithm on data from LIGO interferometers
Authors: Aasi, J; Davies, G S; LIGO Scientific Collaboration and Virgo Collaboration
Abstract: We report results of a wideband search for periodic gravitational waves from isolated neutron stars within the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational waves interact very weakly with matter, the search is unimpeded by dust and concentrations of stars. One search disk (A) is 6.87° in diameter and centered on 20h10m54.71s+33°33′25.29′′, and the other (B) is 7.45° in diameter and centered on 8h35m20.61s−46°49′25.151′′. We explored the frequency range of 50–1500 Hz and frequency derivative from 0 to −5×10−9 Hz/s. A multistage, loosely coherent search program allowed probing more deeply than before in these two regions, while increasing coherence length with every stage. Rigorous followup parameters have winnowed the initial coincidence set to only 70 candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolated gravitationalwave emitter, and 95% confidence level upper limits were placed on continuouswave strain amplitudes. Near 169 Hz we achieve our lowest 95% C.L. upper limit on the worstcase linearly polarized strain amplitude h0 of 6.3×10−25, while at the high end of our frequency range we achieve a worstcase upper limit of 3.4×10−24 for all polarizations and sky locations.
Description: Copyright © 2016 American Physical Society and reproduced in accordance with the publisher copyright policy
20160215T00:00:00Z
Aasi, J
Davies, G S
LIGO Scientific Collaboration and Virgo Collaboration

Directional limits on persistent gravitational waves from Advanced LIGO's first observing run
https://dspace.lib.cranfield.ac.uk:443/handle/1826/11786
Title: Directional limits on persistent gravitational waves from Advanced LIGO's first observing run
Authors: Abbott, B P; Davies, G S; LIGO Scientific Collaboration and Virgo Collaboration
Abstract: We employ gravitationalwave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the Advanced Laser Interferometer Gravitational Wave Observatory’s (aLIGO) first observing run. We also search for persistent gravitational waves from point sources with only minimal assumptions over the 20–1726 Hz frequency band. Finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90% confidence. For broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range
F
α
,
Θ
(
f
)
<
(
0.1
–
56
)
×
10
−
8
erg
cm
−
2
s
−
1
Hz
−
1
(
f
/
25
Hz
)
α
−
1
depending on the sky location
Θ
and the spectral power index
α
. For extended sources, we report upper limits on the fractional gravitational wave energy density required to close the Universe of
Ω
(
f
,
Θ
)
<
(
0.39
–
7.6
)
×
10
−
8
sr
−
1
(
f
/
25
Hz
)
α
depending on
Θ
and
α
. Directed searches for narrowband gravitational waves from astrophysically interesting objects (Scorpius X1, Supernova 1987 A, and the Galactic Center) yield median frequencydependent limits on strain amplitude of
h
0
<
(
6.7
,
5.5
,
and
7.0
)
×
10
−
25
, respectively, at the most sensitive detector frequencies between 130–175 Hz. This represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case.
20170324T00:00:00Z
Abbott, B P
Davies, G S
LIGO Scientific Collaboration and Virgo Collaboration

Tests of General Relativity with GW150914
https://dspace.lib.cranfield.ac.uk:443/handle/1826/11785
Title: Tests of General Relativity with GW150914
Authors: Abbott, B P; Davies, G S; LIGO Scientific Collaboration and Virgo Collaboration
Abstract: The LIGO detection of GW150914 provides an unprecedented opportunity to study the twobody motion of a compactobject binary in the largevelocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary blackhole merger in general relativity. We find that the final remnant’s mass and spin, as determined from the lowfrequency (inspiral) and highfrequency (postinspiral) phases of the signal, are mutually consistent with the binary blackhole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the leastdamped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized generalrelativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitationalwave phase in the dynamical regime and we determine the first empirical bounds on several highorder postNewtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%confidence lower bound of
10
13
km
. In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strongfield regime of gravity.
Description: Copyright © 2016 American Physical Society and reproduced in accordance with the publisher copyright policy
20160530T23:00:00Z
Abbott, B P
Davies, G S
LIGO Scientific Collaboration and Virgo Collaboration

The basic physics of the binary black hole merger GW150914
https://dspace.lib.cranfield.ac.uk:443/handle/1826/11784
Title: The basic physics of the binary black hole merger GW150914
Authors: Abbott, B P; Davies, G S; LIGO Scientific Collaboration and Virgo Collaboration
Abstract: The first direct gravitationalwave detection was made by the Advanced Laser Interferometer Gravitational Wave Observatory on September 14, 2015.
The GW150914 signal was strong enough to be apparent,
without using any waveform model, in the filtered detector strain data.
Here those features of the signal visible in these data are used, along with only such concepts from Newtonian and General Relativity as are accessible to anyone with a general physics background.
The simple analysis presented here is consistent with the fully generalrelativistic analyses published elsewhere, in showing that the signal was produced by the inspiral and subsequent merger of two black holes.
The black holes were each of approximately 35 Msun, still orbited each other as close as 350 km apart and subsequently merged to form a single black hole.
Similar reasoning, directly from the data, is used to roughly estimate how far these black holes were from the Earth, and the energy that they radiated in gravitational waves.
Description: CC BY 4.0
20161003T23:00:00Z
Abbott, B P
Davies, G S
LIGO Scientific Collaboration and Virgo Collaboration