LSC logo - click to go to LSC homepage

LIGO Data Release associated with GRB051103

This page has been prepared by the LIGO Scientific Collaboration (LSC) to make data associated with two LIGO gravitational wave detectors taken around the time of GRB051103 available to the broader community.

Information about GRB051103

Summary of Observation

GRB 051103 was a short-duration, hard-spectrum gamma-ray burst (GRB) which occurred at 09:25:42 UTC on 3 November 2005 (Hurley et al. 2010) and was possibly located in the nearby galaxy M81, at a distance of 3.6 Mpc from Earth (Fig 1 from paper). It was observed by instruments on seven different spacecraft.

Two LIGO detectors were taking science-quality data during the 2190 seconds surrounding GRB051103: the 2km detector at LIGO Hanford Observatory (LHO), known as H2, and the 4km detector at LIGO Livingston Observatory (LLO), known as L1.

Data from these two LIGO detectors were searched for coincident signals consistent with a gravitational wave incident on both detectors.

It is widely believed that most short-hard GRBs result from the gravitational-radiation-induced coalescence of a binary system containing either two neutron stars or one neutron star and a black hole, so we focus on that scenario here. In such a scenario, gravitational waves would arrive at the earth within a few seconds of the gamma rays, so we look within a 6-second interval around the GRB time.

Times in the 6-second interval between 09:25:37 and 09:25:43 UTC on 3 November 2005 are referred to as "on source". This is where we search for a signal associated with GRB051103. There are 324 6-second intervals that are referred to as "Off source" times, selected between 08:54:25 and 09:30:55 UTC (excluding the on-source time and a buffer region around it). These are used to estimate the background distribution of random noise triggers that are also present in the "on source" interval.

As reported in the LIGO publication, no signal was observed above background in the LIGO data.

LIGO data contain, in addition to potentially detectable gravitational wave signals, non-stationary, non-Gaussian noise. Noise fluctuations can register as "triggers", at a rate high enough that they can be accidentally coincident (within fractions of a second) between the H2 and L1 detectors - the background that can fake a signal. Coincident triggers are observed in the "on-source" observation time. However, the rate and significance ("loudness") of those triggers is statistically consistent with those from "off-source" times, where we expect to see only background. Hence, we observe no loud signal above background in the LIGO data.

Gravitational-Wave Detector Data

  • The calibrated data from the LIGO detectors that were used for our GRB051103 analysis is provided here for scientists who wish to do their own analysis. Any publication making use of such data should properly credit the LIGO Scientific Collaboration. We request that anyone interested in publishing anything using these data please first consult with us at datainfo@ligo.org.
  • Note that proper analysis and interpretation of this data requires careful consideration of the detector noise -- which is non-white and non-stationary -- as well as the response of the detectors, which depends on the arrival direction and polarization content of the incoming gravitational wave.
  • Here we provide raw data on the locations and orientations of the detectors, excerpted from the file LALDetectors.h contained in the LALSuite analysis library, as well as some further notes and illustrations of the detector geometry.
  • The overall fractional uncertainty in amplitude calibration is estimated at 25% for both H2 and L1 data, in the band between 40 and 2000 Hz (and uncalibrated outside this band). This is significantly larger than typical science run calibration uncertainties (see e.g., Calibration of the LIGO Gravitational Wave Detectors in the Fifth Science Run) as fewer calibration measurements were available from the data taking around the GRB051103 time.
  • The data files can be found in this data file repository.
  • The data are provided in two formats: HDF5 and gzipped ascii text. Many data analysis environments can read in data from HDF5 files, including Python (see the h5py package), MATLAB, C/C++, and IDL. Links to example python scripts for reading and plotting the HDF5 files can be found below.

Strain data at 16384 Hz

Strain h(t) time series for individual detectors (H2 and L1), starting at GPS 815043278 (Thu Nov 03 08:54:25 GMT 2005), duration 2190 sec, sampled at 16384 Hz, and high-pass filtered to remove the dominant noise below 20 Hz.

Strain data at 4096 Hz

Strain h(t) time series for individual detectors (H2 and L1), starting at GPS 815045078 (Thu Nov 03 09:24:25 GMT 2005), duration 256 sec, sampled at 4096 Hz, and even more high-pass filtered to remove the dominant noise below 30 Hz.

Noise Spectra

The one-sided detector strain noise amplitude spectra around the time of GRB051103, as hdf5, gzipped ascii text files and plots (png and pdf). The vertical scale is strain per sqrt Hz.

Spectrograms and Omegagrams

Spectrogams of the strain h(t) time series for individual detectors, starting at GPS 815045078 (Thu Nov 03 09:24:25 GMT 2005), duration 256 sec, sampled at 4096 Hz:
H2_spectrogram.png and H2_spectrogram.pdf; L1_spectrogram.png and L1_spectrogram.pdf
More figures and information.

Omegagrams are time-frequency plots of the sort shown above. See their definition and further plots.

Data quality

Data quality for individual detectors, starting at GPS 815043278 (Thu Nov 03 08:54:25 GMT 2005):
None of these data are vetoed due to problems with the data quality; all data from both detectors during this time are unvetoed and are of good science quality.

Search triggers

If GRB051103 was produced by the binary merger (coalescence) of a neutron star with a black hole or another neutron star in M81, it would produce a characteristic Compact Binary Coalescence (CBC) waveform in the LIGO detectors. See the description of event triggers from the CBC search in data around GRB051103.

Data documentation and example scripts


About the Instruments and Collaborations

The LIGO Observatory

The Laser Interferometer Gravitational-Wave Observatory (LIGO) consists of two widely separated installations within the United States -- one in Hanford Washington and the other in Livingston, Louisiana -- operated in unison as a single observatory. LIGO is operated by the LIGO Laboratory, a consortim of the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT). Funded by the National Science Foundation, LIGO is an international resource for both physics and astrophysics.

The GEO600 Detector

The GEO600 project aims at the direct detection of gravitational waves by means of a laser interferometer of 600 m armlength located near Hannover, Germany. Besides collecting data for gravitational wave searches, the GEO600 detector has been used to develop and test advanced instrumentation for gravitational wave detection.

The LIGO Scientific Collaboration

The LIGO Scientific Collaboration (LSC) is a group of scientists seeking to make the first direct detection of gravitational waves, use them to explore the fundamental physics of gravity, and develop the emerging field of gravitational wave science as a tool of astronomical discovery. The LSC works toward this goal through research on, and development of techniques for, gravitational wave detection; and the development, commissioning and exploitation of gravitational wave detectors. The LSC carries out the science of the LIGO and GEO600 Observatories. Participation in the LSC is open to all interested scientists and engineers from educational and research institutions.

Time-frequency plot
Omegagram of strain data from H2 near the time of GRB051103. (More information on omegagrams).

Time-frequency plot
Omegagram of strain data from L1 near the GRB051103 time. The red blob near the bottom between 2 and 4 seconds is a detector data glitch which is mostly below 40 Hz. Our BNS templates start at 40 Hz because the detector noise rises sharply at lower frequencies, so they are largely insensitive to these kinds of glitches.

Time-frequency plot
Omegagram of strain data from H1 near a simulated BNS signal at 3.5 Mpc injected in to the detector. More information on omegagrams.

Find us on Facebook   Follow us on Twitter    Follow us on YouTube