S6 Stochastic Hardware Injections
During LIGO's 6th Science Run (S6), simulated signals were added to the
LIGO detectors for testing and calibration. The simulated signals are
known as hardware injections, because they were created by manipulating
mirrors in the arms of the interferometers. Times of hardware injections
are marked in LIGO data files by injection data quality channels. See the
injection bit mask
Stochastic signals are described in
S5 stochastic search paper in this way:
"A stochastic background of gravitational waves is expected to
arise from a superposition of a large number of unresolved
gravitational-wave sources of astrophysical and cosmological origin.
It is expected to carry unique signatures from the earliest epochs in the
evolution of the universe, inaccessible to the standard astrophysical
S6 Stochastic Injections
Isotropic stochastic signals were injected
into the LIGO interferometers at planned times during S6.
Each stochastic injection was generated with a flat energy spectrum,
and is characterized by an energy density
which is normalized by the critical energy density of the universe.
In addition, there was also an anisotropic stochastic injection performed on
July 20, 2010.
The times of the
S6 hardware injections may be seen in the S6 hardware injection segment lists:
Detailed parameters are available for the subset of injections made on
October 6, 2010. A detailed description of the October 6 stochastic injections
may be found in LIGO technical note
In addition, the parameters of the October 6 injections may be seen
in the table below:
|GPS Start ||GPS End ||Ω0
|970381131 ||970382155 || 8.8 × 10−3
|970382931 ||970384131 ||
|970384731 ||970385755 ||0.14