# Glossary¶

BBH

Binary black hole system, a binary system composed of two black holes.

BNS

Binary neutron star, a binary system composed of two neutron stars.

BNS range

A figure of merit to describe the sensitivity of a gravitational-wave detector to BNS mergers, defined as the average luminosity distance at which the merger of two $$1.4~M_\odot$$ objects would be detectable with a signal to noise ratio of 8. See also Burst range.

Burst range

A figure of merit to describe the sensitivity of a gravitational-wave detector to unmodeled bursts, defined with reference to optimistic models of gravitational wave emissions from stellar collapse as the average luminosity distance at which a monochromatic burst at 150 Hz with a fluence of $$E_\mathrm{GW} = 10^{-2} M_\odot c^2$$ would be detectable with a signal to noise ratio of 8. See also BNS range.

CBC

Compact binary coalescence.

FITS

Flexible Image Transport System, a format for astronomical tables, images, and multidimensional data sets.

GCN

The Gamma-ray Coordinates Network (https://gcn.gsfc.nasa.gov), a portal for discoveries and observations of astronomical transients. Historically, GCN has served high-energy satellites but now also other electromagnetic wavelengths and also gravitational-wave, cosmic ray, and neutrino facilities.

GCN Circular

A human-readable astronomical bulletin distributed through GCN.

GCN Notice

GraceDB

Gravitational Wave Candidate Event Database (https://gracedb.ligo.org), the official public marshal portal for LIGO/Virgo candidates.

GRB

Gamma-ray burst.

HEALPix

Hierarchical Equal Area isoLatitude Pixelation, a scheme for indexing positions on the unit sphere.

HEN

High Energy Neutrino, particularly in the context of multi-messenger GW+HEN follow-up.

KAGRA

Kamioka Gravitational Wave Detector, 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.

MassGap

Compact binary systems with at least one compact object whose mass is in the hypothetical “mass gap” between neutron stars and black holes, defined here as 3-5 solar masses.

NSBH

Neutron star black hole, a binary system composed of one neutron star and one black hole.

primary

When referring to the two component compact objects or the masses of the two component compact objects in a binary, the primary is the more massive one, i.e., $$m_1 \geq m_2$$. See secondary.

secondary

When referring to the two component compact objects or the masses of the two component compact objects in a binary, the secondary is the less massive one, i.e., $$m_2 \leq m_1$$. See primary.

SN

Supernova.

SNR

Signal-to-noise ratio, here applied to gravitational-wave signals. It is defined the square root of the integral over frequency of the power spectral density of the gravitational-wave signal over the integral over frequency of the average power spectral density of the noise.

Virgo

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

VOEvent

An XML format for describing astronomical transients. For the specification, see the official VOEvent IVOA Recommendation.

VTP

VOEvent Transport Protocol, a simple TCP-based protocol for sending and receiving VOEvents, used by GCN. For the specification, see the official VTP IVOA recommendation.