After data collection, several independently-measured terrestrial contributions to the detector noise were subtracted
from the LIGO data using Wiener filtering. This subtraction removed calibration
lines and 60 Hz AC power mains harmonics from both LIGO data streams. At times near GW170817, the sensitivity of LIGO-Hanford
was particularly improved by the subtraction of laser pointing noise; several broad peaks in the 150 - 800 Hz
region were effectively removed, increasing the Binary Neutron Star horizon distance of that detector by 26%.
In addition, a short instrumental noise transient appeared in the LIGO-Livingston detector 1.1 s before
the coalescence time of GW170817. This transient noise, or glitch, produced a very brief (less than 5ms)
saturation in a digital-to-analog converter. This glitch has been removed from the noise subtracted data.
Below are links to strain h(t) time series centered at GPS 1187008064.
All cleaned data files have been shortened to a total duration of 2048 seconds.
The H1 and L1 noise subtraction procedure introduces excess noise at frequencies below 20 Hz. Users should restrict analysis to frequencies above 20 Hz.
The H1 cleaned data include times corrupted by a window function used as part of the cleaning procedure. This impacts roughly the last 150 seconds of the H1 cleaned data.
Due to V1's smaller coupling factor to gravitational waves from the sky direction of GW170817, and the lower detector sensitivity, the signal is
below the noise level and is thus not visible in the Virgo data.
† The ± 30 msec window for peak amplitude is due to different arrival time in each of the three detectors.
Strain data before noise subtraction
These files contain data before noise subtraction. These data were produced in low-latency, and used by the search pipelines to evaluate event significance.
A short instrumental noise transient appeared in the LIGO-Livingston detector 1.1 s
before the coalescence time of GW170817. This transient noise, or glitch, produced a very brief
(less than 5ms) saturation in a digital-to-analog converter.
This glitch is present in the strain data before
To evaluate the significance of GW170817, the CBC search analyses applied a
window function to zero out the data around the glitch.
This Tukey window uses the following parameters: zero the data +/- 0.1 seconds
(0.2 seconds total in length) around the glitch time 1187008881.389 and the roll-off time is 0.5 seconds
either side of the zeroed data. This inverse Tukey window is presented in Figure 2 of the GW170817
Some Burst searches may use a CAT2 data quality flag
to remove this glitch from search results. There is an active Burst CAT2 data quality flag at
LIGO-Livingston starting at 1187008880 and extending to 1187008884.
In this case also GEO600 data are released. The GEO600 calibration uncertainty is estimated to be within 15% in amplitude and 15 deg in phase in the 1–4 kHz band.
Below are links to strain h(t) time series centered at GPS 1187008882.
md5 checksums may be used to ensure files are correctly downloaded (the md5 checksums for the G1 files may be found here).
In GEO600, the signal is below the noise level because of the lower detector sensitivity and is thus not visible in the G1 data. These data have not been used for the discovery of the GW170817 event and the subsequent parameter estimation analyses. However, GEO600 data were used in the paper arxiv:1805.11579 to place upper limits on the amplitude and spectral energy density of a possible post-merger signal. This analysis uses only the high-frequency signal component and only 1 s of data around the coalescence time of the merger.
GEO600 data are characterised by an excess noise at low frequency for about 100 seconds after the start of the second data segment (after GPS 1187008219).
For G1, the data quality flag 'DATA' refers to when the detector was UP. At the time of the event the detector was not in science mode. The reason for GEO data quality not being in Science mode is because of a software maintenance investigation regarding an issue with the squeezer phase loop error point which was introducing technical noise below 1kHz. Data quality above 1kHz (the relevant frequency band for the current study that used GEO data) was not compromised.
Before noise subtraction, 4096 Hz
4096 seconds (event signal reaches peak amplitude 2048.43 seconds ± 30 msec from start†)