The General Coordinates Network (GCN), formerly known as the Gamma-ray burst Coordinates Network, is an open-source platform created by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

to receive and transmit alerts about astronomical

transient Transience or transient may refer to: Music * ''Transient'' (album), a 2004 album by Gaelle * ''Transience'' (Steven Wilson album), 2015 * Transience (Wreckless Eric album) Science and engineering * Transient state, when a process variable or ...

phenomena. This includes

neutrino A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that i ...

detections by observatories such as

IceCube The IceCube Neutrino Observatory (or simply IceCube) is a neutrino observatory developed by the University of Wisconsin–Madison and constructed at the Amundsen–Scott South Pole Station in Antarctica. The project is a recognized CERN experim ...

Super-Kamiokande Super-Kamiokande (abbreviation of Super-Kamioka Neutrino Detection Experiment, also abbreviated to Super-K or SK; ) is a neutrino detector, neutrino observatory located Kamioka Observatory, under Mount Ikeno near the city of Hida, Gifu, Hida, ...

gravitational wave Gravitational waves are oscillations of the gravitational field that Wave propagation, travel through space at the speed of light; they are generated by the relative motion of gravity, gravitating masses. They were proposed by Oliver Heaviside i ...

events from the

LIGO The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Prior to LIG ...

Virgo Virgo may refer to: Arts and entertainment * Virgo (film), a 1970 Egyptian film * Virgo (character), several Marvel Comics characters * Virgo Asmita, a character in the manga ''Saint Seiya: The Lost Canvas'' * ''Virgo'' (album), by Virgo Four, ...

and

KAGRA The Kamioka Gravitational Wave Detector (KAGRA) is a large interferometer designed to detect gravitational waves predicted by the general theory of relativity. KAGRA is a Michelson interferometer that is isolated from external disturbances: its mi ...

interferometers, and

gamma-ray burst In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic events occurring in distant Galaxy, galaxies which represent the brightest and most powerful class of explosion in the universe. These extreme Electromagnetic radiation, ele ...

s observed by

Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian and naturalized American physicist, renowned for being the creator of the world's first artificial nuclear reactor, the Chicago Pile-1, and a member of the Manhattan Project ...

Swift Swift or SWIFT most commonly refers to: * SWIFT, an international organization facilitating transactions between banks ** SWIFT code * Swift (programming language) * Swift (bird), a family of birds It may also refer to: Organizations * SWIF ...

INTEGRAL In mathematics, an integral is the continuous analog of a Summation, sum, which is used to calculate area, areas, volume, volumes, and their generalizations. Integration, the process of computing an integral, is one of the two fundamental oper ...

. One of the main goals is to allow for follow-up observations of an event by other observatories, in hope to observe multi-messenger events. GCN has its origins in the BATSE coordinates distribution network (BACODINE). The Burst And Transient Source Experiment (

BATSE The Compton Gamma Ray Observatory (CGRO) was a space observatory detecting photons with energies from 20 k eV to 30 GeV, in Earth orbit from 1991 to 2000. The observatory featured four main telescopes in one spacecraft, covering X-r ...

) was a scientific instrument on the ''

Compton Gamma-Ray Observatory The Compton Gamma Ray Observatory (CGRO) was a space observatory detecting photons with energies from 20 k eV to 30 GeV, in Earth orbit from 1991 to 2000. The observatory featured four main telescopes in one spacecraft, covering X- ...

'' (CGRO), and BACODINE monitored the BATSE real-time telemetry from CGRO. The first function of BACODINE was calculating the

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...

(RA) and

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...

(dec) locations for GRBs that it detected, and distributing those locations to sites around the world in real-time. Since the de-orbiting of the CGRO, this function of BACODINE is no longer operational. The second function of BACODINE was collecting right ascension and declination locations of GRBs detected by spacecraft other than CGRO, and then distributing that information. With this functionality, the original BACODINE name was changed to the more general name GCN. It later evolved to include alerts from non-GRB observatories and was sometimes referred to as GCN/TAN (for Transient Astronomy Network).

Design

The GCN relies on two types of alerts: notices and circulars. Notices are machine-readable alerts, which are distributed in real time; they typically include only basic information about the event. Circulars are brief human-readable alerts, which are distributed (typically by e-mail) with a low latency but not in real time; they can also contain predictions, requests for follow-up observations from other observatories, or advertise observing plans. The current version of the GCN relies on

Kafka Franz Kafka (3 July 1883 – 3 June 1924) was a novelist and writer from Prague who was Jewish, Austrian, and Czech and wrote in German. He is widely regarded as a major figure of 20th-century literature. His work fuses elements of real ...

to distribute the alerts, improving on previous versions which used three separate protocols. The infrastructure for sending the alerts towards the GCN is managed by the respective observatories. For the historical gamma-ray burst observatories, which are based on spacecraft, this involves sending the information to a ground station;

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...

was the center in charge of sending the notices from GRB observatories.

Current participants

As of April 2023, 14 missions are sending alerts to the GCN : *''INTErnational Gamma-Ray Astrophysics Laboratory'' (

), a gamma-ray telescope *''

'', a gamma-ray telescope, which provides data products not previously available from prior missions, including spectra, images, and

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

s. *

, an American gamma-ray telescope * AGILE, an Italian gamma-ray telescope * HAWC, a ground-based gamma-ray and

cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...

observatory in Mexico *

Calorimetric Electron Telescope The CALorimetric Electron Telescope (CALET) is a space telescope being mainly used to perform high precision observations of electrons and gamma rays. It tracks the trajectory of electrons, protons, nuclei, and gamma rays and measures their dire ...

, a Japanese

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

and gamma-ray detector based on the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

InterPlanetary Network The InterPlanetary Network (IPN) is a group of spacecraft equipped with gamma ray burst (GRB) detectors. By timing the arrival of a burst at several spacecraft, its precise location can be found. The precision for determining the direction of a G ...

(IPN) Position Notices from ''

WIND Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

'' (Konus), a Russian gamma-ray telescope * MAXI, a Japanese

x-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

telescope mounted on the International Space Station * SuperNova Early Warning System (SNEWS), a consortium of neutrino facilities for alerts from

core-collapse supernovae A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion. The original obj ...

, a neutrino experiment based in the South Pole *

, a Japanese neutrino observatory *

, an international network of

detectors * GECAM, a group of two Chinese x-ray and gamma-ray observatories designed for follow-up of gravitational wave events *

Microlensing Observations in Astrophysics Microlensing Observations in Astrophysics (MOA) is a collaborative project between researchers in New Zealand and Japan, led by Professor Yasushi Muraki of Nagoya University. They use gravitational microlensing, microlensing to observe dark mat ...

(MOA) project, with alerts on

microlensing Gravitational microlensing is an astronomical phenomenon caused by the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronome ...

events Past spacecraft and instruments that participated in GCN include ''

Array of Low Energy X-ray Imaging Sensors The Array of Low Energy X-ray Imaging Sensors (ALEXIS, also known as P89-1B, COSPAR 1993-026A, SATCAT 22638) X-ray telescope featured curved mirrors whose multilayer coatings reflected and focused low-energy X-rays or extreme ultraviolet (EUV) lig ...

'' (''ALEXIS''), ''

BeppoSAX BeppoSAX was an Italian–Dutch satellite for X-ray astronomy which played a crucial role in resolving the origin of gamma-ray bursts (GRBs), the most energetic events known in the universe. It was the first X-ray mission capable of simultaneousl ...

'', the Imaging Compton Telescope (COMPTEL) on CGRO, the X-Ray/Gamma-Ray Spectrometer (XGRS) on ''

NEAR Shoemaker ''Near Earth Asteroid Rendezvous – Shoemaker'' (''NEAR Shoemaker''), renamed after its 1996 launch in honor of planetary scientist Eugene Merle Shoemaker, Eugene Shoemaker, was a Robotic spacecraft, robotic space probe designed by the Johns ...

'', the ''

High Energy Transient Explorer High Energy Transient Explorer 2 (HETE-2; also known as Explorer 79) was a NASA astronomical satellite with international participation (mainly Japan and France). The satellite bus for the first HETE-1 was designed and built by AeroAstro, Inc. ...

'' (WMM and SXC), the ''

Rossi X-ray Timing Explorer The Rossi X-ray Timing Explorer (RXTE) was a NASA satellite that observed the time variation of astronomical X-ray sources, named after physicist Bruno Rossi. The RXTE had three instruments — an All-Sky Monitor, the High-Energy X-ray Timing ...

'' (PCA and ASM) and ''

Ulysses Ulysses is the Latin name for Odysseus, a legendary Greek hero recognized for his intelligence and cunning. He is famous for his long, adventurous journey home to Ithaca after the Trojan War, as narrated in Homer's Odyssey. Ulysses may also refer ...

''.

References

{{Reflist

External links

GCN Homepage
Gamma-ray telescopes Gamma-ray bursts Astrophysics