Gravitational Wave Open Science Center

S6 Continuous Wave Hardware Injections

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.

Continuous Wave Injections

Continuous Wave (CW) injections (also known as pulsar injections) were added throughout S6. Each CW injection corresponds to a simulation of a gravitational wave signal of the form expected from a rapidly rotating, isolated neutron star (often observed as a radio pulsar).

NOTE: There is no HW_CW injection bit set to indicate when CW (pulsar) injections are on, since they were essentially always on during S6. This is in contrast to the other types of S6 hardware injections, which do have bits set to indicate when they are on; see: the timeline information.

The full set of injected pulsars may be seen on the pulsar injection parameters page.

The page provides lists of pulsar injection parameters. Simulated CW gravitational waves from all 10 pulsars were add to the LIGO data throughout S6. There were some times when attempted injections failed because of computer or network failures. The recovery of similar pulsar hardware injections is described in arXiv:0909.3583 and arXiv:1110.0208. The recovery of a few simulated pulsars in Virgo data is described in ApJ 737 93, and a search for pulsars in S6 data is reported in arXiv:1309.4027.

The parameters are defined as in Dupuis & Woan, 2005. The parameters f0 and phi0 are both defined at a reference time corresponding to the beginning of LIGO's 3rd science run: GPS 751680013 == Nov 01 2003 00:00:00 UTC. Two additional parameters are also listed for each simulated pulsar:

Aplus = 0.5*h0*(1 + cos2(iota))
Across = h0*cos(iota)

Blind Injection

There was one blind pulsar injection in S6. The injection spans the time from GPS 969837280 to the end of S6. Its parameters are included on the pulsar injection parameters page.