15 research outputs found
Selection effects in resolving Galactic binaries with LISA
Using several realisations of the Galactic population of close white dwarf
binaries, we have explored the selection bias for resolved binaries in the LISA
data stream. We have assumed a data analysis routine that is capable of
identifying binaries that have a signal to noise ratio of at least 5 above a
confusion foreground of unresolved binaries. The resolved population of
binaries is separated into a subpopulation over 1000 binaries that have a
measureable chirp and another subpopulation over 20,000 binaries that do not.
As expected, the population of chirping binaries is heavily skewed toward high
frequency, high chirp mass systems, with little or no preference for nearby
systems. The population of non-chirping binaries is still biased toward
frequencies above about 1 mHz. There is an overabundance of higher mass systems
than is present in the complete Galactic population.Comment: 9 pages, 8 figures, GWDAW 11 proceeding
Searches for continuous gravitational waves from nine young supernova remnants
We describe directed searches for continuous gravitational waves in data from
the sixth LIGO science data run. The targets were nine young supernova remnants
not associated with pulsars; eight of the remnants are associated with
non-pulsing suspected neutron stars. One target's parameters are uncertain
enough to warrant two searches, for a total of ten. Each search covered a broad
band of frequencies and first and second frequency derivatives for a fixed sky
direction. The searches coherently integrated data from the two LIGO
interferometers over time spans from 5.3-25.3 days using the matched-filtering
F-statistic. We found no credible gravitational-wave signals. We set 95%
confidence upper limits as strong (low) as on intrinsic
strain, on fiducial ellipticity, and on
r-mode amplitude. These beat the indirect limits from energy conservation and
are within the range of theoretical predictions for neutron-star ellipticities
and r-mode amplitudes.Comment: Science summary available at
http://www.ligo.org/science/Publication-S6DirectedSNR/index.ph
Relativistic Binaries in Globular Clusters
Galactic globular clusters are old, dense star systems typically containing
10\super{4}--10\super{7} stars. As an old population of stars, globular
clusters contain many collapsed and degenerate objects. As a dense population
of stars, globular clusters are the scene of many interesting close dynamical
interactions between stars. These dynamical interactions can alter the
evolution of individual stars and can produce tight binary systems containing
one or two compact objects. In this review, we discuss theoretical models of
globular cluster evolution and binary evolution, techniques for simulating this
evolution that leads to relativistic binaries, and current and possible future
observational evidence for this population. Our discussion of globular cluster
evolution will focus on the processes that boost the production of hard binary
systems and the subsequent interaction of these binaries that can alter the
properties of both bodies and can lead to exotic objects. Direct {\it N}-body
integrations and Fokker--Planck simulations of the evolution of globular
clusters that incorporate tidal interactions and lead to predictions of
relativistic binary populations are also discussed. We discuss the current
observational evidence for cataclysmic variables, millisecond pulsars, and
low-mass X-ray binaries as well as possible future detection of relativistic
binaries with gravitational radiation.Comment: 88 pages, 13 figures. Submitted update of Living Reviews articl
A directed search for gravitational waves from Scorpius X-1 with initial LIGO
19 pages, 8 figuresInternational audienceWe present results of a search for continuously-emitted gravitational radiation, directed at the brightest low-mass X-ray binary, Scorpius X-1. Our semi-coherent analysis covers 10 days of LIGO S5 data ranging from 50-550 Hz, and performs an incoherent sum of coherent -statistic power distributed amongst frequency-modulated orbital sidebands. All candidates not removed at the veto stage were found to be consistent with noise at a 1% false alarm rate. We present Bayesian 95% confidence upper limits on gravitational-wave strain amplitude using two different prior distributions: a standard one, with no a priori assumptions about the orientation of Scorpius X-1; and an angle-restricted one, using a prior derived from electromagnetic observations. Median strain upper limits of 1.3e-24 and 8e-25 are reported at 150 Hz for the standard and angle-restricted searches respectively. This proof of principle analysis was limited to a short observation time by unknown effects of accretion on the intrinsic spin frequency of the neutron star, but improves upon previous upper limits by factors of ~1.4 for the standard, and 2.3 for the angle-restricted search at the sensitive region of the detector
Advanced LIGO
The Advanced LIGO gravitational wave detectors are second-generation instruments designed and built for the two LIGO observatories in Hanford, WA and Livingston, LA, USA. The two instruments are identical in design, and are specialized versions of a Michelson interferometer with 4 km long arms. As in Initial LIGO, Fabry–Perot cavities are used in the arms to increase the interaction time with a gravitational wave, and power recycling is used to increase the effective laser power. Signal recycling has been added in Advanced LIGO to improve the frequency response. In the most sensitive frequency region around 100 Hz, the design strain sensitivity is a factor of 10 better than Initial LIGO. In addition, the low frequency end of the sensitivity band is moved from 40 Hz down to 10 Hz. All interferometer components have been replaced with improved technologies to achieve this sensitivity gain. Much better seismic isolation and test mass suspensions are responsible for the gains at lower frequencies. Higher laser power, larger test masses and improved mirror coatings lead to the improved sensitivity at mid and high frequencies. Data collecting runs with these new instruments are planned to begin in mid-2015
Erratum: Searches for continuous gravitational waves from nine young supernova remnants (2015, ApJ, 813, 39)
We describe directed searches for continuous gravitational waves in data from the sixth LIGO science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the remnants are associated with non-pulsing suspected neutron stars. One target's parameters are uncertain enough to warrant two searches, for a total of ten. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering F-statistic. We found no credible gravitational-wave signals. We set 95% confidence upper limits as strong (low) as on intrinsic strain, on fiducial ellipticity, and on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes
Erratum: "Searches for Continuous Gravitational Waves from Nine Young Supernova Remnants" (2015, ApJ, 813, 39)
Equation (7) of the published article (Aasi et al. 2015) is in error; it should read (Equation presented). The upper limits on ò presented in the published article are unaffected by this error. Equation (8) of the published article is in error; it should read (Equation presented) The upper limits on α presented in Figure 3 and Table 4 of the published article were computed incorrectly. The revised Figure 3 (bottom) shows the corrected upper limits on α for the G266.2-1.2 (Vela Jr.) wide search. The revised Table 4 is provided here. The correct lowest upper limit on α (quoted in the Abstract of the published article) is 3 × 10-6. Figure 4 shows the incorrect and corrected upper limits on α for the G266.2-1.2 (Vela Jr.) wide search, which have been surpassed by upper limits from Abbott et al. (2019)
Search for gravitational wave ringdowns from perturbed intermediate mass black holes in LIGO-Virgo data from 2005–2010
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