603 research outputs found
Large-Scale Image Processing with the ROTSE Pipeline for Follow-Up of Gravitational Wave Events
Electromagnetic (EM) observations of gravitational-wave (GW) sources would
bring unique insights into a source which are not available from either channel
alone. However EM follow-up of GW events presents new challenges. GW events
will have large sky error regions, on the order of 10-100 square degrees, which
can be made up of many disjoint patches. When searching such large areas there
is potential contamination by EM transients unrelated to the GW event.
Furthermore, the characteristics of possible EM counterparts to GW events are
also uncertain. It is therefore desirable to be able to assess the statistical
significance of a candidate EM counterpart, which can only be done by
performing background studies of large data sets. Current image processing
pipelines such as that used by ROTSE are not usually optimised for large-scale
processing. We have automated the ROTSE image analysis, and supplemented it
with a post-processing unit for candidate validation and classification. We
also propose a simple ad hoc statistic for ranking candidates as more likely to
be associated with the GW trigger. We demonstrate the performance of the
automated pipeline and ranking statistic using archival ROTSE data. EM
candidates from a randomly selected set of images are compared to a background
estimated from the analysis of 102 additional sets of archival images. The
pipeline's detection efficiency is computed empirically by re-analysis of the
images after adding simulated optical transients that follow typical light
curves for gamma-ray burst afterglows and kilonovae. We show that the automated
pipeline rejects most background events and is sensitive to simulated
transients to limiting magnitudes consistent with the limiting magnitude of the
images
Cost-benefit analysis for commissioning decisions in GEO600
Gravitational wave interferometers are complex instruments, requiring years
of commissioning to achieve the required sensitivities for the detection of
gravitational waves, of order 10^-21 in dimensionless detector strain, in the
tens of Hz to several kHz frequency band. Investigations carried out by the
GEO600 detector characterisation group have shown that detector
characterisation techniques are useful when planning for commissioning work. At
the time of writing, GEO600 is the only large scale laser interferometer
currently in operation running with a high duty factor, 70%, limited chiefly by
the time spent commissioning the detector. The number of observable
gravitational wave sources scales as the product of the volume of space to
which the detector is sensitive and the observation time, so the goal of
commissioning is to improve the detector sensitivity with the least possible
detector down time. We demonstrate a method for increasing the number of
sources observable by such a detector, by assessing the severity of
non-astrophysical noise contaminations to efficiently guide commissioning. This
method will be particularly useful in the early stages and during the initial
science runs of the aLIGO and adVirgo detectors, as they are brought up to
design performance.Comment: 17 pages, 17 figures, 2 table
A List of Galaxies for Gravitational Wave Searches
We present a list of galaxies within 100 Mpc, which we call the Gravitational
Wave Galaxy Catalogue (GWGC), that is currently being used in follow-up
searches of electromagnetic counterparts from gravitational wave searches. Due
to the time constraints of rapid follow-up, a locally available catalogue of
reduced, homogenized data is required. To achieve this we used four existing
catalogues: an updated version of the Tully Nearby Galaxy Catalog, the Catalog
of Neighboring Galaxies, the V8k catalogue and HyperLEDA. The GWGC contains
information on sky position, distance, blue magnitude, major and minor
diameters, position angle, and galaxy type for 53,255 galaxies. Errors on these
quantities are either taken directly from the literature or estimated based on
our understanding of the uncertainties associated with the measurement method.
By using the PGC numbering system developed for HyperLEDA, the catalogue has a
reduced level of degeneracies compared to catalogues with a similar purpose and
is easily updated. We also include 150 Milky Way globular clusters. Finally, we
compare the GWGC to previously used catalogues, and find the GWGC to be more
complete within 100 Mpc due to our use of more up-to-date input catalogues and
the fact that we have not made a blue luminosity cut.Comment: Accepted for publication in Classical and Quantum Gravity, 13 pages,
7 figure
Implications For The Origin Of GRB 051103 From LIGO Observations
We present the results of a LIGO search for gravitational waves (GWs)
associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst
(GRB) whose electromagnetically determined sky position is coincident with the
spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for
short-hard GRBs include compact object mergers and soft gamma repeater (SGR)
giant flares. A merger progenitor would produce a characteristic GW signal that
should be detectable at the distance of M81, while GW emission from an SGR is
not expected to be detectable at that distance. We found no evidence of a GW
signal associated with GRB 051103. Assuming weakly beamed gamma-ray emission
with a jet semi-angle of 30 deg we exclude a binary neutron star merger in M81
as the progenitor with a confidence of 98%. Neutron star-black hole mergers are
excluded with > 99% confidence. If the event occurred in M81 our findings
support the the hypothesis that GRB 051103 was due to an SGR giant flare,
making it the most distant extragalactic magnetar observed to date.Comment: 8 pages, 3 figures. For a repository of data used in the publication,
go to: https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=15166 . Also see
the announcement for this paper on ligo.org at:
http://www.ligo.org/science/Publication-GRB051103/index.ph
Swift follow-up observations of candidate gravitational-wave transient events
We present the first multi-wavelength follow-up observations of two candidate
gravitational-wave (GW) transient events recorded by LIGO and Virgo in their
2009-2010 science run. The events were selected with low latency by the network
of GW detectors and their candidate sky locations were observed by the Swift
observatory. Image transient detection was used to analyze the collected
electromagnetic data, which were found to be consistent with background.
Off-line analysis of the GW data alone has also established that the selected
GW events show no evidence of an astrophysical origin; one of them is
consistent with background and the other one was a test, part of a "blind
injection challenge". With this work we demonstrate the feasibility of rapid
follow-ups of GW transients and establish the sensitivity improvement joint
electromagnetic and GW observations could bring. This is a first step toward an
electromagnetic follow-up program in the regime of routine detections with the
advanced GW instruments expected within this decade. In that regime
multi-wavelength observations will play a significant role in completing the
astrophysical identification of GW sources. We present the methods and results
from this first combined analysis and discuss its implications in terms of
sensitivity for the present and future instruments.Comment: Submitted for publication 2012 May 25, accepted 2012 October 25,
published 2012 November 21, in ApJS, 203, 28 (
http://stacks.iop.org/0067-0049/203/28 ); 14 pages, 3 figures, 6 tables;
LIGO-P1100038; Science summary at
http://www.ligo.org/science/Publication-S6LVSwift/index.php ; Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p110003
Gravitational Waves From Known Pulsars: Results From The Initial Detector Era
We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.United States National Science FoundationScience and Technology Facilities Council of the United KingdomMax-Planck-SocietyState of Niedersachsen/GermanyAustralian Research CouncilInternational Science Linkages program of the Commonwealth of AustraliaCouncil of Scientific and Industrial Research of IndiaIstituto Nazionale di Fisica Nucleare of ItalySpanish Ministerio de Economia y CompetitividadConselleria d'Economia Hisenda i Innovacio of the Govern de les Illes BalearsNetherlands Organisation for Scientific ResearchPolish Ministry of Science and Higher EducationFOCUS Programme of Foundation for Polish ScienceRoyal SocietyScottish Funding CouncilScottish Universities Physics AllianceNational Aeronautics and Space AdministrationOTKA of HungaryLyon Institute of Origins (LIO)National Research Foundation of KoreaIndustry CanadaProvince of Ontario through the Ministry of Economic Development and InnovationNational Science and Engineering Research Council CanadaCarnegie TrustLeverhulme TrustDavid and Lucile Packard FoundationResearch CorporationAlfred P. Sloan FoundationAstronom
A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts
associated with high energy neutrinos. Together, these messengers could reveal
new, hidden sources that are not observed by conventional photon astronomy,
particularly at high energy. Our search uses neutrinos detected by the
underwater neutrino telescope ANTARES in its 5 line configuration during the
period January - September 2007, which coincided with the fifth and first
science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed
for candidate gravitational-wave signals coincident in time and direction with
the neutrino events. No significant coincident events were observed. We place
limits on the density of joint high energy neutrino - gravitational wave
emission events in the local universe, and compare them with densities of
merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at
http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGOâs first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts
We outline the scientific motivation behind a search for gravitational waves
associated with short gamma ray bursts detected by the InterPlanetary Network
(IPN) during LIGO's fifth science run and Virgo's first science run. The IPN
localisation of short gamma ray bursts is limited to extended error boxes of
different shapes and sizes and a search on these error boxes poses a series of
challenges for data analysis. We will discuss these challenges and outline the
methods to optimise the search over these error boxes.Comment: Methods paper; Proceedings for Eduardo Amaldi 9 Conference on
Gravitational Waves, July 2011, Cardiff, U
Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
Aims. A transient astrophysical event observed in both gravitational wave
(GW) and electromagnetic (EM) channels would yield rich scientific rewards. A
first program initiating EM follow-ups to possible transient GW events has been
developed and exercised by the LIGO and Virgo community in association with
several partners. In this paper, we describe and evaluate the methods used to
promptly identify and localize GW event candidates and to request images of
targeted sky locations.
Methods. During two observing periods (Dec 17 2009 to Jan 8 2010 and Sep 2 to
Oct 20 2010), a low-latency analysis pipeline was used to identify GW event
candidates and to reconstruct maps of possible sky locations. A catalog of
nearby galaxies and Milky Way globular clusters was used to select the most
promising sky positions to be imaged, and this directional information was
delivered to EM observatories with time lags of about thirty minutes. A Monte
Carlo simulation has been used to evaluate the low-latency GW pipeline's
ability to reconstruct source positions correctly.
Results. For signals near the detection threshold, our low-latency algorithms
often localized simulated GW burst signals to tens of square degrees, while
neutron star/neutron star inspirals and neutron star/black hole inspirals were
localized to a few hundred square degrees. Localization precision improves for
moderately stronger signals. The correct sky location of signals well above
threshold and originating from nearby galaxies may be observed with ~50% or
better probability with a few pointings of wide-field telescopes.Comment: 17 pages. This version (v2) includes two tables and 1 section not
included in v1. Accepted for publication in Astronomy & Astrophysic
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