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Register a new userApplication of a Hough search for continuous gravitational waves on data from the 5th LIGO science run
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We report on an all-sky search for periodic gravitational waves in the frequency range $mathrm{50-1000 Hz}$ with the first derivative of frequency in the range $-8.9 times 10^{-10}$ Hz/s to zero in two years of data collected during LIGOs fifth science run. Our results employ a Hough transform technique, introducing a $chi^2$ test and analysis of coincidences between the signal levels in years 1 and 2 of observations that offers a significant improvement in the product of strain sensitivity with compute cycles per data sample compared to previously published searches. Since our search yields no surviving candidates, we present results taking the form of frequency dependent, 95$%$ confidence upper limits on the strain amplitude $h_0$. The most stringent upper limit from year 1 is $1.0times 10^{-24}$ in the $mathrm{158.00-158.25 Hz}$ band. In year 2, the most stringent upper limit is $mathrm{8.9times10^{-25}}$ in the $mathrm{146.50-146.75 Hz}$ band. This improved detection pipeline, which is computationally efficient by at least two orders of magnitude better than our flagship Einstein$@$Home search, will be important for quick-look searches in the Advanced LIGO and Virgo detector era.
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We report on a comprehensive all-sky search for periodic gravitational waves in the frequency band 100-1500 Hz and with a frequency time derivative in the range of $[-1.18, +1.00]times 10^{-8}$ Hz/s. Such a signal could be produced by a nearby spinning and slightly non-axisymmetric isolated neutron star in our galaxy. This search uses the data from the Initial LIGO sixth science run and covers a larger parameter space with respect to any past search. A Loosely Coherent detection pipeline was applied to follow up weak outliers in both Gaussian (95% recovery rate) and non-Gaussian (75% recovery rate) bands. No gravitational wave signals were observed, and upper limits were placed on their strength. Our smallest upper limit on worst-case (linearly polarized) strain amplitude $h_0$ is ${9.7}times 10^{-25}$ near 169 Hz, while at the high end of our frequency range we achieve a worst-case upper limit of ${5.5}times 10^{-24}$. Both cases refer to all sky locations and entire range of frequency derivative values.
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 $6.87^circ$ in diameter and centered on $20^textrm{h}10^textrm{m}54.71^textrm{s}+33^circ3325.29$, and the other (B) is $7.45^circ$ in diameter and centered on $8^textrm{h}35^textrm{m}20.61^textrm{s}-46^circ4925.151$. We explored the frequency range of 50-1500 Hz and frequency derivative from $0$ to $-5times 10^{-9}$ Hz/s. A multi-stage, 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 initial coincidence set to only 70 candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolated gravitational wave emitter, and 95% confidence level upper limits were placed on continuous-wave strain amplitudes. Near $169$ Hz we achieve our lowest 95% CL upper limit on worst-case linearly polarized strain amplitude $h_0$ of $6.3times 10^{-25}$, while at the high end of our frequency range we achieve a worst-case upper limit of $3.4times 10^{-24}$ for all polarizations and sky locations.
This paper reports on an unmodeled, all-sky search for gravitational waves from merging intermediate mass black hole binaries (IMBHB). The search was performed on data from the second joint science run of the LIGO and Virgo detectors (July 2009 - October 2010) and was sensitive to IMBHBs with a range up to $sim 200$ Mpc, averaged over the possible sky positions and inclinations of the binaries with respect to the line of sight. No significant candidate was found. Upper limits on the coalescence-rate density of nonspinning IMBHBs with total masses between 100 and $450 mbox{M}_{odot}$ and mass ratios between $0.25$ and $1,$ were placed by combining this analysis with an analogous search performed on data from the first LIGO-Virgo joint science run (November 2005 - October 2007). The most stringent limit was set for systems consisting of two $88 mbox{M}_{odot}$ black holes and is equal to $0.12 mbox{Mpc}^{-3} mbox{Myr}^{-1}$ at the $90%$ confidence level. This paper also presents the first estimate, for the case of an unmodeled analysis, of the impact on the search range of IMBHB spin configurations: the visible volume for IMBHBs with nonspinning components is roughly doubled for a population of IMBHBs with spins aligned with the binarys orbital angular momentum and uniformly distributed in the dimensionless spin parameter up to 0.8, whereas an analogous population with antialigned spins decreases the visible volume by $sim 20%,$.
We report on an all-sky search for continuous gravitational waves in the frequency band 20-2000,Hz and with a frequency time derivative in the range of $[-1.0, +0.1]times10^{-8}$,Hz/s. Such a signal could be produced by a nearby, spinning and slightly non-axisymmetric isolated neutron star in our galaxy. This search uses the LIGO data from the first six months of Advanced LIGOs and Advanced Virgos third observational run, O3. No periodic gravitational wave signals are observed, and 95% confidence-level (CL) frequentist upper limits are placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude $h_0$ are $~1.7times10^{-25}$ near 200,Hz. For a circularly polarized source (most favorable orientation), the lowest upper limits are $sim6.3times10^{-26}$. These strict frequentist upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest 95% CL upper limits on the strain amplitude are $sim1.times10^{-25}$. These upper limits improve upon our previously published all-sky results, with the greatest improvement (factor of $sim$2) seen at higher frequencies, in part because quantum squeezing has dramatically improved the detector noise level relative to the second observational run, O2. These limits are the most constraining to date over most of the parameter space searched.
Isolated spinning neutron stars, asymmetric with respect to their rotation axis, are expected to be sources of continuous gravitational waves. The most sensitive searches for these sources are based on accurate matched filtering techniques, that assume the continuous wave to be phase-locked with the pulsar beamed emission. While matched filtering maximizes the search sensitivity, a significant signal-to-noise ratio loss will happen in case of a mismatch between the assumed and the true signal phase evolution. Narrow-band algorithms allow for a small mismatch in the frequency and spin-down values of the pulsar while integrating coherently the entire data set. In this paper we describe a narrow-band search using LIGO O2 data for the continuous wave emission of 33 pulsars. No evidence for a continuous wave signal has been found and upper-limits on the gravitational wave amplitude, over the analyzed frequency and spin-down volume, have been computed for each of the targets. In this search we have surpassed the spin-down limit for some of the pulsars already present in the O1 LIGO narrow-band search, such as J1400textminus6325 J1813textminus1246, J1833textminus1034, J1952+3252, and for new targets such as J0940textminus5428 and J1747textminus2809. For J1400textminus6325, J1833textminus1034 and J1747textminus2809 this is the first time the spin-down limit is surpassed.
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