# Glossary¶

- BBH¶
Binary black hole, a binary system composed of two black holes. See BH.

- BH¶
Black hole.

- BNS¶
Binary neutron star, a binary system composed of two neutron stars. See NS.

- burst¶
In the context of gravitational waves, a signal candidate that is detected without a template and without prior knowledge of the waveform. Examples of potential sources of gravitational-wave bursts include high mass BBH mergers, core-collapse supernovae, and cosmic string cusps.

- KAGRA¶
Kamioka Gravitational Wave Detector (see KAGRA home page), an underground gravitational-wave detector in the Kamioka mine in Japan.

- LHO¶
LIGO Hanford Observatory (see LHO observatory home page), site of a 4 km gravitational-wave detector in Hanford, Washington, USA.

- LLO¶
LIGO Livingston Observatory (see LLO observatory home page), site of a 4 km gravitational-wave detector in Livingston, Louisiana, USA.

- NS¶
Neutron star.

- NSBH¶
Neutron star black hole, a binary system composed of one neutron star and one black hole. See NS, BH.

- range¶
A figure of merit to describe the sensitivity of a gravitational-wave detector to a given source population at cosmologically significant distances. It is defined as the radius \(R\) of a Euclidean sphere with the volume equal to the sensitive volume \(V_z\). It may be written as:

\[R = \left(\frac{3 V_z}{4 \pi}\right)^{1/3}.\]- sensitive volume¶
A figure of merit for the sensitivity of a gravitational-wave detector or a network of detectors. It is defined as the space-time volume surveyed per unit detector time, and may be expressed as (cf. [1]):

\[V_\mathrm{z} = \frac{ \int_{z < z^*(\Theta)} p(\Theta) \frac{dV_C}{dz} \frac{dz}{1 + z} }{\int p(\Theta) d\Theta}.\]Here, \(\Theta\) is the set of parameters that describe the gravitational-wave signal (merger time, sky location, orbital elements, masses, and spins) and \(p(\Theta)\) is the redshift-independent population model for those parameters. The term \(\frac{dV_C}{dz}\) is differential comoving volume per unit redshift. The function \(z^*(\Theta)\) is the

*threshold redshift*, or the redshift at which a binary with parameters \(\Theta\) is just at the limit of detection. The factor of \({1 + z}\) in the denominator accounts for time dilation from the source frame to the detector frame.If a population of sources occurs at a fixed rate per unit comoving volume per unit proper time \(\dot{n}\), then the rate of observed events in the detector frame is \(\dot{n} V_z\).

- Virgo¶
Virgo Observatory (see Virgo observatory home page), site of a 3 km gravitational-wave detector in Cascina, Italy.