Data release for event GW150914

This page has been prepared by the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration to inform the broader community about a confirmed astrophysical event observed by the gravitational-wave detectors, and to make the data around that time available for others to analyze. There is also a technical details page about the data linked below, and feel free to contact us. This dataset has the Digital Object Identifier (doi) http://dx.doi.org/10.7935/K5MW2F23


Summary of Observation

The event occurred at GPS time 1126259462 == September 14 2015, 09:50:45 UTC. The false alarm rate is estimated to be less than 1 event per 203,000 years, equivalent to a significance of 5.1 sigma. The event was detected in data from the LIGO Hanford and LIGO Livingston observatories.

  • There are Science Summaries, covering the information below in ordinary language.
  • There is a one page factsheet about GW150914, summarizing the event.

  • How to Use this Page

    • Click on the section headings below to show available data files.
    • There are lots of data files available in the sections below, look for the word DATA.
    • Click on each thumbnail image for larger image.
    • See the papers linked below for full information, references, and meaning.
    • Many of the data files linked below have heterogeneous formatting; if you have any questions, please contact us.


    The G150914 detection paper:

    Observation of Gravitational Waves from a Binary Black Hole Merger

    For full details see LIGO DCC, arXiv, or Phys. Rev. Letters
    This paper and all the companion papers can also be found at papers.ligo.org.

    Estimated source parameters

    QuantityValueUpper/Lower error
    estimate
    Unit
    Primary black hole mass 36 +5 -4 M sun
    Secondary black hole mass 29 +4 -4 M sun
    Final black hole mass 62 +4 -4 M sun
    Final black hole spin 0.67+0.05 -0.07
    Luminosity distance 410 +160 -180 Mpc
    Source redshift, z 0.09+0.03 -0.04
    Energy radiated 3+0.5 -0.5 M sun

    TABLE I. Estimated source parameters for GW150914. We report the median value as well as the range of the 90% credible interval. Masses are measured in the source frame; to convert masses to detector frame, multiply by (1 + z). The source redshift assumes standard cosmology.


    click for DATA

    click for DATA (L1 only)

    click for DATA (Numerical relativity)

    click for DATA (Numerical relativity)

    click for DATA

    click for DATA

    FIG. 1. The gravitational-wave event GW150914 observed by the LIGO Hanford (H1, left column panels) and Livingston (L1, right column panels) detectors. Times are shown relative to September 14, 2015 at 09:50:45 UTC. For visualization, all time series are filtered with a 35–350 Hz band-pass filter to suppress large fluctuations outside the detectors’ most sensitive frequency band, and band-reject filters to remove the strong instrumental spectral lines seen in the Fig. 3 spectra.

    • Top row, left: H1 strain. Top row, right: L1 strain. GW150914 arrived first at L1 and 6.9 (+0.5 −0.4) ms later at H1; for a visual comparison the H1 data are also shown, shifted in time by this amount and inverted (to account for the detectors’ relative orientations).
    • Second row: Gravitational-wave strain projected onto each detector in the 35–350 Hz band. Solid lines show a numerical relativity waveform for a system with parameters consistent with those recovered from GW150914 confirmed by an independent calculation. Shaded areas show 90% credible regions for two waveform reconstructions: one that models the signal as a set of sine-Gaussian wavelets and one that models the signal using binary-black-hole template waveforms. These reconstructions have a 95% overlap.
    • Third row: Residuals after subtracting the filtered numerical relativity waveform from the filtered detector time series.
    • Bottom row: A time-frequency decomposition of the signal power associated with GW150914. Both plots show a signal with frequency increasing with time.


    Numerical relativity DATA
    Reconstructed DATA

    separation DATA
    velocity DATA

    FIG. 2. Left: Estimated gravitational-wave strain amplitude from GW150914 projected onto H1. This shows the full bandwidth of the waveforms, without the filtering used for Fig. 1. Right: The Keplerian effective black hole separation in units of Schwarzschild radii and the effective relative velocity.

    Hanford DATA
    Livingston DATA

    FIG.3. The average measured strain-equivalent noise, or sensitivity, of the Advanced LIGO detectors during the time analyzed to determine the significance of GW150914 (Sept 12 - Oct 20, 2015). Hanford (H1) is shown in red, Livingston (L1) in blue. The solid traces represent the median sensitivity and the shaded regions indicate the 5th and 95th percentile over the analysis period. The narrowband features in the spectra are due to known mechanical resonances, mains power harmonics, and injected signals used for calibration.


    Search Result C3 DATA
    Search Background C3 DATA
    Search Result C2 C3 DATA
    Search Background C2 C3 DATA

    Search Results DATA

    FIG. 4. Search results from the generic transient search (left) and the binary coalescence search (right). These histograms show the number of candidate events (orange markers) and the mean number of background events in the search class where GW150914 was found (black lines) as a function of the search detection statistic and with a bin width of 0.2. The scales on the top give the significance of an event in Gaussian standard deviations based on the corresponding noise background . The significance of GW150914 is greater than 5.1 σ and 4.6 σ for the binary coalescence and the generic transient searches, respectively. (Left): Along with the primary search (C3) we also show the results (yellow markers) and background (green curve) for an alternative search that treats events independently of their frequency evolution (C2+C3). The classes C2 and C3 are defined in the text. (Right): The tail in the black-line background of the binary coalescence search is due to random coincidences of GW150914 in one detector with noise in the other detector. (This type of event is practically absent in the generic transient search background because they do not pass the time-frequency consistency requirements used in that search.) The blue curve is the background excluding those coincidences, which is used to assess the significance of the second strongest event candidate.


    The data from the observatories from which the science is derived:

    Gravitational-Wave Strain Data

    Strain Data at 4096 Hz

    Strain h(t) time series centered at GPS 1126259462:
    DurationHanfordLivingston
    32 seconds
    approx 1 Mbyte
    DATA hdf5
    DATA gwf
    DATA txt.gz
    DATA hdf5
    DATA gwf
    DATA txt.gz
    4096 seconds
    approx 134 Mbyte
    DATA hdf5
    DATA gwf
    DATA txt.gz
    DATA hdf5
    DATA gwf
    DATA txt.gz

    Strain Data at 16384 Hz

    Strain h(t) time series centered at GPS 1126259462:
    DurationHanfordLivingston
    32 seconds
    approx 4 Mbyte
    DATA hdf5
    DATA gwf
    DATA txt.gz
    DATA hdf5
    DATA gwf
    DATA txt.gz
    4096 seconds
    approx 536 Mbyte
    DATA hdf5
    DATA gwf
    DATA txt.gz
    DATA hdf5
    DATA gwf
    DATA txt.gz


    Tutorial on Signal Processing with Gravitational-Wave Strain Data

    The numerical relativity waveform used in this tutorial can be obtained as a plain-text file, here, where the first column is the time in seconds relative to the peak of the waveform, and the second column is the (unitless) strain. This waveform was obtained from the SXS Gravitational Waveform Database, courtesy of the SXS Collaboration (please see Acknowledgements in that link). It corresponds to waveform ID SXS:BBH:0305, with mass ratio m1/m2 = 1.221 and aligned spins. Its time axis has been rescaled for a system with detector frame total mass of 74.6 solar masses, and the overall amplitude and phase are adjusted, all to get good agreement with the data at both detectors.


    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 consortium 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.


    Observing Gravitational-Wave Transient GW150914 with Minimal Assumptions

    For full details see LIGO DCC or arXiv.

    Hanford DATA
    Livingston DATA
    Figure 10: The cWB point estimate for the waveform and the 90% credible interval from the BW analysis. The reconstructed waveforms and shown data are whitened using estimated noise curves for each detector at the time of the event.


    GW150914: First Results from the Search for Binary Black Hole Coalescence with Advanced LIGO

    For full details see LIGO DCC or arXiv.


    Properties of the binary black hole merger GW150914

    For full details see LIGO DCC or arXiv.


    The Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations Surrounding GW150914

    For full details see LIGO DCC or arXiv

    DATA

    FIG 3. The rate at which sensitive time-volume accumulates with redshift.

    R1 DATA, gstlal | pycbc
    R2 DATA, gstlal | pycbc
    R DATA, gstlal | pycbc

    FIG 4. The posterior density on the rate of GW150914-like BBH inspirals, R1 (green), G197392-like BBH inspirals, R2 (red), and the inferred total rate, R = R1 + R2 (blue).

    Flat DATA, gstlal | pycbc
    Powerlaw DATA, gstlal | pycbc

    FIG 5. Sensitivity of the inferred BBH coalescence rate to the assumed astrophysical distribution BBH masses. The curves represent the posterior assuming that BBH masses are flat in log (m1)- log (m2) (blue; “Flat”), are exactly GW150914-like or G197392- like as described in Section 2 (green; “Reference”), or are distributed as in Eq. (20) (red; “Power Law”).


    Astrophysical Implications of the Binary Black-Hole Merger GW150914

    For full details see LIGO DCC or arXiv


    Tests of general relativity with GW150914

    For full details see LIGO DCC or arXiv.


    GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes

    For full details see LIGO DCC or arXiv or Phys. Rev. Letters.

    DATA
    FIG. 1: Expected sensitivity of the network of advanced LIGO and Virgo detectors to the Fiducial field model. Energy density spectra are shown in blue (solid for the total background; dashed for the residual background assuming final advanced LIGO and Virgo sensitivity). The pink shaded region shows the 90% CL statistical uncertainty propagated from the local rate measurement. The black curves are power-law integrated sensitivities for the network expected for the two first observing runs O1 and O2, and for 2 years at the design sensitivity in O5 (O3 and O4 are not significantly different than O5); see Table I. If the astrophysical background spectrum intersects a black line, it has expected SNR ≥ 1.


    Calibration of the Advanced LIGO detectors for the discovery of the binary black-hole merger GW150914

    For full details see the paper: LIGO DCC or arXiv.


    Characterization of Transient Noise in Advanced LIGO Relevant to Gravitational Wave Signal GW150914

    For full details see LIGO DCC or arXiv.

    Hanford DATA
    Livingston DATA

    FIG.1 The average measured strain-equivalent noise, or sensitivity, of the Advanced LIGO detectors during the time analyzed to determine the significance of GW150914 (Sept 12 - Oct 20, 2015). Hanford (H1) is shown in red, Livingston (L1) in blue. The solid traces represent the median sensitivity and the shaded regions indicate the 5th and 95th percentile over the analysis period. The narrowband features in the spectra are due to known mechanical resonances, mains power harmonics, and injected signals used for calibration


    High-energy Neutrino Follow-up Search of Gravitational Wave Event GW150914 with IceCube and ANTARES

    For full details see LIGO DCC


    GW150914: The Advanced LIGO Detectors in the Era of First Discoveries

    For full details see LIGO DCC or arXiv. or Phys. Rev. Letters.

    Anthology of papers describing the technology of LIGO can be found at:
        Quest for Detection: Articles from Review of Scientific Instruments .


    Sky location probability maps

    Localization and broadband follow-up of the gravitational-wave transient GW150914

    For full details see LIGO DCC.

    Four pipelines produced sky localization information, known as CWB, LIB, BAYESTAR, and LALInference. Their sky coverage comparison is shown below, in equatorial coordinates:

    Comparison of different GW sky maps, showing the 90% credible level contours for each algorithm. This orthographic projection centered on the centroid of the LIB localization. The inset shows the distribution of the polar angle θHL (equivalently, the arrival time difference ∆tHL). Sky at the time of the event, with the LALInference skymap, contoured in deciles of probability. View is from the South Atlantic Ocean, North at the top, with the Sun rising and the Milky Way diagonally from NW to SE.

    The skymaps can be visualized in astronomical context with the Skymap Viewer, as in the right-hand image: CWB, LIB, BAYESTAR, LALInference.

    The skymaps are represented as HEALPIX-FITS files in equatorial frame, available gzipped:

    A python library for reading such files is healpy. A very simple healpy code to work with LIGO-Virgo skymaps is here. A large number of simulated skymaps is available here.


    Audio Files

    Files are in wav format, with data whitened and band-passed to 20 - 300 Hz. These files can be generated from the data using the GW150914 tutorial that is linked above.
    • Observed waveform, whitened and band-passed 20 Hz to 300 Hz, for H1 and L1.
    • Observed waveform, whitened and band-passed 20 Hz to 300 Hz, and shifted up by 400 Hz, for H1 and L1.
    • Observed waveform, whitened and band-passed 40 Hz to 400 Hz, and shifted up by 200 Hz, for H1 and L1.
    • Best fit theoretical waveform, whitened and band-passed, and whitened and shifted up by 400 Hz
    • Median reconstructions of the event, and whitened. H in left channel, L in right channel: BayesWave.
    • Best-fit (MAP) waveforms from paper P1500218, H in left channel, L in right channel: Unwhitened and whitened.

    The following audio files have been produced from a newer tutorial (June 2016) entitled "Tutorial on Signal Processing with Open Data from any O1 BBH event". See the tutorials section for more details.


    There is a technical details page about the data linked above, and feel free to contact us.