The O1 Data Release

Run Overview

  • O1 dates: 2015 Sep 12th 0:00 UTC (GPS 1126051217) to 2016 Jan 19 16:00 UTC (GPS 1137254417)
  • Data is available from two detectors, H1 and L1 (Virgo data was not collected during O1)
  • The O1 data set is available at the original 16 KHz and the downsampled 4KHz sample rates.
  • This is the first observing run of Advanced LIGO
  • We released three events from this run, two confirmed (and one possible) binary black hole mergers

Get O1 Data

New to O1 16KHz GWF Files

The O1 16KHz GWF files (ending with extension .gwf) have new channel names that differ from the standard names used in S5, S6 and O1 4KH z GWF files.


Channel names found inside GWF files

O1 (4KHz samples per second) O1 (16KHz samples per second)
{ifo}:LOSC-STRAIN {ifo}:GWOSC-16KHZ_R1_STRAIN
{ifo}:LOSC-DQMASK {ifo}:GWOSC-16KHZ_R1_DQMASK
{ifo}:LOSC-INJMASK {ifo}:GWOSC-16KHZ_R1_INJMASK
NOTES:
  • {ifo} is a place holder for either H1 or L1, e.g., H1:GWOSC-16KHZ_R1_STRAIN or L1:GWOSC-16KHZ_R1_STRAIN.
  • The _R1_ substring in the O1 16KHz channel names representes the revision number of the channel name.
  • The strain data in both the O1 4KHz and O1 16KHz data sets are based on the same C02 calibration.
  • The naming conventions used for the HDF5 files is unchanged for the O1 16KHZ data set.

O1 Detector Status

For details about the status of LIGO at this time, see:
  • Configuration: GW150914: The Advanced LIGO Detectors in the Era of First Discoveries Phys. Rev. Lett.; arXiv
  • Sensitivity: The Sensitivity of the Advanced LIGO Detectors at the Beginning of Gravitational Wave Astronomy Phys. Rev. D; arXiv
  • Calibration: Calibration of the Advanced LIGO detectors for the discovery of the binary black-hole merger GW150914 Phys. Rev. D; arXiv

Astrophysical Results

O1 includes at least two detections of binary black hole mergers. An overview of compact binary coalescence results in O1 detections can be found in:
  • Observation of Gravitational Waves from a Binary Black Hole Merger Phys. Rev. Lett.; arXiv
  • GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence, Phys. Rev. Lett.; arXiv
  • Binary Black Hole Mergers in the first Advanced LIGO Observing Run, Phys. Rev. X; arXiv
  • Upper limits on the rates of binary neutron star and neutron-star--black-hole mergers from Advanced LIGO's first observing run, Ap. J. Lett.; arXiv
  • All-sky search for short gravitational-wave bursts in the first Advanced LIGO run, Phys. Rev. D; arXiv
For a full list of O1 results papers by the LSC and Virgo collaborations, see:

Data Quality

Executive Summary: The DATA flag indicates if data is available from LOSC. In general, a search for binary black hole events will analyze data that passes the DATA and the tests called CBC_CAT1 and CBC_CAT2.

See Characterization of transient noise in Advanced LIGO relevant to gravitational wave signal GW150914 for a description of data quality around GW150914. The methods and studies described in this paper were also conducted to characterise the entire data set from O1.

LIGO data quality categories, or flags, are defined by each analysis group: Compact Binary Coalescence (CBC), Burst, Continuous Waves (CW) and Stochastic. This is because periods of noisy data will affect each type of analysis differently. For each flag, LOSC data files contain a corresponding 1 Hz time-series that marks times that pass the flag as a "1" (good data), and times that fail the flag as a "0" (bad data). A full list of O1 data quality categories can be seen on the O1 data quality definitions page. The details of each category are described in the references linked below. However, as a rough guide:

  • DATA (Data Available): Failing this level indicates that LIGO data are not publicly available because the instruments were not operating in an acceptable condition. For O1, this is equivalent to Category 1.
  • CAT1 (Category 1): Failing a data quality check at this category indicates a critical issue with a key detector component not operating in its nominal configuration. Since these times indicate a major known problem these times are identical for each data analysis group. Times that fail CAT1 flags are not available as LIGO open data -- not available at this web site.
  • CAT2 (Category 2): Failing a data quality check at this category indicates times when there is a known, understood physical coupling to the gravitational wave channel. This might include times of high seismic activity.
  • CAT3 (Category 3): Failing a data quality check at this category indicates times when there is statistical coupling to the gravitational wave channel which is not fully understood.

In general, data quality levels are defined in a cumulative way: a time which fails a given category automatically fails all higher categories. For example, if the only known problem with a given time fails a burst category 2 flag, then the data is said to pass DATA and BURST_CAT1, but fails BURST_CAT2 and BURST_CAT3. However, the different analysis groups are independent: if something fails at CAT2_BURST, then it can pass CAT2_CBC.

These graduated categories of quality allow a data pipeline to adjust its behavior depending on the data quality. For example running the numerical search (template matching) against all the data segments that pass CAT1, but ignoring any candidate events from data that do not pass CAT3. This strategy allows long sections of data to be used, increasing search efficiency.

Note to LSC members: Conventionally, hardware injections are vetoed by CAT flags so that searches do not see them. However LOSC strain data provides h(t) at these times: therefore a search with LOSC data will find lots of chirps, to be compared with the lists of injections -- see below.

For information on how to use data quality information:

  • Characterization of Transient Noise in Advanced LIGO Relevant to Gravitational Wave Signal GW150914 CQG, or arXiv
  • Effects of Data Quality Vetoes on a Search for Compact Binary Coalescences in Advanced LIGO's First Observing Run arXiv.
  • Step 3 and Step 4 of the introductory tutorial show how to apply data quality flags
  • Data Quality definitions for the O1 data set.
  • Plot and download segment lists from Timeline

Hardware Injections

The O1 data set contains simulated astrophysical signals, known as hardware injections, used for testing and calibration. For an example, see the Find a Hardware Injection Tutorial. For complete documentation, see: Segment lists of times that do NOT have hardware injections; each line of the file is GPS start time, GPS end time, and the diefference of those.
  • NO_CBC_HW segment lists: H1 | L1
  • NO_BURST_HW segment lists: H1 | L1
  • The NO_DETCHAR_HW segment lists: H1 | L1
  • The NO_CW_HW segment lists: H1 | L1

Instrumental Spectral Lines

A power spectral density of LIGO data typically shows a number of spectral lines. Many of these are associated with known instrumental resonances. The O1 instrumental spectral lines page gives an explanation, and catalog, of these instrumental lines.

Technical Details

LOSC 4KHz strain data have been repackaged and downsampled from 16384 Hz to 4096 Hz. Advanced LIGO data are not calibrated or valid below 10 Hz or above 5 kHz, and the data sampled at 4096 Hz are not valid above 2 kHz. In most searches for astrophysical sources, data below 20 Hz are not used because the noise is too high. More detailed information about the data set can be seen on the Technical Details page.

Acknowledge

To acknowledge the use of O1 data, see the Acknowledgement Page.

Data Set DOI: https://doi.org/10.7935/K57P8W9D