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Characterization of the LIGO detectors during their sixth science run
Aasi, J,Abadie, J,Abbott, B P,Abbott, R,Abbott, T,Abernathy, M R,Accadia, T,Acernese, F,Adams, C,Adams, T,Adhikari, R X,Affeldt, C,Agathos, M,Aggarwal, N,Aguiar, O D,Ajith, P,Allen, B,Allocca, A,Ceron IOP Publishing 2015 Classical and quantum gravity Vol.32 No.11
<P>In 2009-2010, the Laser Interferometer Gravitational-Wave Observatory (LIGO) operated together with international partners Virgo and GEO600 as a network to search for gravitational waves (GWs) of astrophysical origin. The sensitivity of these detectors was limited by a combination of noise sources inherent to the instrumental design and its environment, often localized in time or frequency, that couple into the GW readout. Here we review the performance of the LIGO instruments during this epoch, the work done to characterize the detectors and their data, and the effect that transient and continuous noise artefacts have on the sensitivity of LIGO to a variety of astrophysical sources.</P>
The characterization of Virgo data and its impact on gravitational-wave searches
Aasi, J,Abadie, J,Abbott, B P,Abbott, R,Abbott, T D,Abernathy, M,Accadia, T,Acernese, F,Adams, C,Adams, T,Addesso, P,Adhikari, R,Affeldt, C,Agathos, M,Agatsuma, K,Ajith, P,Allen, B,Allocca, A,Ceron, E IOP Publishing 2012 Classical and quantum gravity Vol.29 No.15
Aasi, J.,Abadie, J.,Abbott, B. P.,Abbott, R.,Abbott, T.,Abernathy, M. R.,Accadia, T.,Acernese, F.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Affeldt, C.,Agathos, M.,Aggarwal, N.,Aguiar, O. D.,Aji American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.2
<P>Searches for a stochastic gravitational-wave background (SGWB) using terrestrial detectors typically involve cross-correlating data from pairs of detectors. The sensitivity of such cross-correlation analyses depends, among other things, on the separation between the two detectors: the smaller the separation, the better the sensitivity. Hence, a colocated detector pair is more sensitive to a gravitational-wave background than a noncolocated detector pair. However, colocated detectors are also expected to suffer from correlated noise from instrumental and environmental effects that could contaminate the measurement of the background. Hence, methods to identify and mitigate the effects of correlated noise are necessary to achieve the potential increase in sensitivity of colocated detectors. Here we report on the first SGWB analysis using the two LIGO Hanford detectors and address the complications arising from correlated environmental noise. We apply correlated noise identification and mitigation techniques to data taken by the two LIGO Hanford detectors, H1 and H2, during LIGO's fifth science run. At low frequencies, 40-460 Hz, we are unable to sufficiently mitigate the correlated noise to a level where we may confidently measure or bound the stochastic gravitational-wave signal. However, at high frequencies, 460-1000 Hz, these techniques are sufficient to set a 95% confidence level upper limit on the gravitational-wave energy density of Omega(f) < 7.7 x 10(-4) (f/900 Hz)(3), which improves on the previous upper limit by a factor of similar to 180. In doing so, we demonstrate techniques that will be useful for future searches using advanced detectors, where correlated noise (e.g., from global magnetic fields) may affect even widely separated detectors.</P>
Aasi, J.,Abbott, B. P.,Abbott, R.,Abbott, T.,Abernathy, M. R.,Acernese, F.,Ackley, K.,Adams, C.,Adams, T.,Adams, T.,Addesso, P.,Adhikari, R. X.,Adya, V.,Affeldt, C.,Agathos, M.,Agatsuma, K.,Aggarwal, American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.2
<P>In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational-wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed assuming both that polarization parameters are completely unknown and that they are known with some uncertainty, as derived from x-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of 2 below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.</P>
First low frequency all-sky search for continuous gravitational wave signals
Aasi, J.,Abbott, B. P.,Abbott, R.,Abbott, T. D.,Abernathy, M. R.,Acernese, F.,Ackley, K.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Adya, V. B.,Affeldt, C.,Agathos, M.,Agatsuma, K.,Aggarwal, N.,A American Physical Society 2016 Physical Review D Vol.93 No.4
<P>In this paper we present the results of the first low frequency all-sky search of continuous gravitational wave signals conducted on Virgo VSR2 and VSR4 data. The search covered the full sky, a frequency range between 20 and 128 Hz with a range of spin-down between -1.0 x 10(-10) and +1.5 x 10(-11) Hz/s, and was based on a hierarchical approach. The starting point was a set of short fast Fourier transforms, of length 8192 s, built from the calibrated strain data. Aggressive data cleaning, in both the time and frequency domains, has been done in order to remove, as much as possible, the effect of disturbances of instrumental origin. On each data set a number of candidates has been selected, using the Frequency Hough transform in an incoherent step. Only coincident candidates among VSR2 and VSR4 have been examined in order to strongly reduce the false alarm probability, and the most significant candidates have been selected. The criteria we have used for candidate selection and for the coincidence step greatly reduce the harmful effect of large instrumental artifacts. Selected candidates have been subject to a follow-up by constructing a new set of longer fast Fourier transforms followed by a further incoherent analysis, still based on the Frequency Hough transform. No evidence for continuous gravitational wave signals was found, and therefore we have set a population-based joint VSR2-VSR4 90% confidence level upper limit on the dimensionless gravitational wave strain in the frequency range between 20 and 128 Hz. This is the first all-sky search for continuous gravitational waves conducted, on data of ground-based interferometric detectors, at frequencies below 50 Hz. We set upper limits in the range between about 10(-24) and 2 x 10(-23) at most frequencies. Our upper limits on signal strain show an improvement of up to a factor of similar to 2 with respect to the results of previous all-sky searches at frequencies below 80 Hz.</P>
SEARCHES FOR CONTINUOUS GRAVITATIONAL WAVES FROM NINE YOUNG SUPERNOVA REMNANTS
Aasi, J.,Abbott, B. P.,Abbott, R.,Abbott, T.,Abernathy, M. R.,Acernese, F.,Ackley, K.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Adya, V.,Affeldt, C.,Agathos, M.,Agatsuma, K.,Aggarwal, N.,Aguiar, IOP Publishing 2015 The Astrophysical journal Vol.813 No.1
<P>We describe directed searches for continuous gravitational waves (GWs) in data from the sixth Laser Interferometer Gravitational-wave Observatory (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 10. 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. -statistic. We found no evidence of GW signals. We set 95% confidence upper limits as strong (low) as 4 x 10(-25) on intrinsic strain, 2 x 10(-7) on fiducial ellipticity, and 4 x 10(-5) 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.</P>
Enhanced sensitivity of the LIGO gravitational wave detector by using squeezed states of light
Aasi, J.,Abadie, J.,Abbott, B. P.,Abbott, R.,Abbott, T. D.,Abernathy, M. R.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Affeldt, C.,Aguiar, O. D.,Ajith, P.,Allen, B.,Amador Ceron, E.,Amariutei, D. Springer Science and Business Media LLC 2013 Nature photonics Vol.7 No.8
Stress Fracture of the Femoral Shaft in Paget’s Disease of Bone: A Case Report
Sarthak Nepal,Atthakorn Jarusriwanna,Aasis Unnanuntana 대한골대사학회 2021 대한골대사학회지 Vol.28 No.2
Paget’s disease of bone (PDB) is a progressive bone disorder characterized by increased osteoclast-mediated bone resorption and abnormal bone formation. Incomplete atypical femoral fracture, appearing radiographically as a stress fracture at the lateral aspect of the femur, is an uncommon low-trauma fracture frequently seen in association with long-term bisphosphonate therapy. We describe the case of a 61-year-old female patient with PDB who developed a stress fracture at the lateral femoral cortex after 5 doses of intravenous bisphosphonate. The conservative treatment plan included discontinuation of bisphosphonate, a continuation of calcium and vitamin D supplementation, and limited weight-bearing for 3 months. The patient’s pain level gradually improved after switching to the new treatment plan. At the latest follow-up, approximately 5 years after the initiation of conservative treatment, the patient remained pain-free, and her PDB was well-controlled. However, the fracture line was still visible on the most recent radiograph. Although it remains unclear whether a stress fracture at the lateral femoral cortex occurred due to bisphosphonate therapy or PDB, this case highlights the importance of careful evaluation of any lesion that appears in PDB patients receiving bisphosphonate therapy.