Plotting segments for a StateVector

Confident detection of gravitational-wave signals is critically dependent on understanding the quality of the data searched. Alongside the strain h(t) data, GWOSC also releases a Data Quality state vector. We can use this to check on the quality of the data from the LIGO Livingston detector around GW170817.

First, we can import the StateVector class:

from gwpy.timeseries import StateVector

and download the state information surrounding GW170817:

data = StateVector.fetch_open_data(
    "L1",
    1187008882 - 100,
    1187008882 + 100,
    verbose=True,
)

Fetched 1 URLs from gwosc.org for [1187008782 .. 1187008982))
Reading data... [Done]

Finally, we make a plot(), passing insetlabels=True to display the bit names inside the axes:

plot = data.plot(insetlabels=True)
ax = plot.gca()
ax.set_xscale("seconds", epoch=1187008882)
ax.axvline(1187008882, color="orange", linestyle="--")
ax.set_title("LIGO-Livingston data quality around GW170817")
plot.show()

This plot shows that for a short time exactly overlapping with GW170817 there was a data quality issue recorded that would negatively impact a search for generic gravitational-wave transients (bursts). For more details on this glitch, and on how it was excised, please see the science summary for GW170817.