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The General Coordinates Network (GCN), formerly known as the Gamma-ray burst Coordinates Network, is an open-source platform created by NASA to receive and transmit alerts about astronomical transient phenomena. This includes neutrino detections by observatories such as IceCube or Super-Kamiokande, gravitational wave events from the LIGO, Virgo and KAGRA interferometers, and gamma-ray bursts observed by Fermi, Swift or INTEGRAL. [1] 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. [2] [3]
GCN has its origins in the BATSE coordinates distribution network (BACODINE). The Burst And Transient Source Experiment (BATSE) was a scientific instrument on the Compton Gamma-Ray Observatory (CGRO), and BACODINE monitored the BATSE real-time telemetry from CGRO. The first function of BACODINE was calculating the right ascension (RA) and declination (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. [4] It later evolved to include alerts from non-GRB observatories and was sometimes referred to as GCN/TAN (for Transient Astronomy Network). [5]
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. [6]
The current version of the GCN relies on Kafka to distribute the alerts, improving on previous versions which used three separate protocols. [7]
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; NASA Goddard Space Flight Center was the center in charge of sending the notices from GRB observatories.
As of April 2023, 14 missions are sending alerts to the GCN : [1]
Past spacecraft and instruments that participated in GCN include Array of Low Energy X-ray Imaging Sensors (ALEXIS), BeppoSAX , the Imaging Compton Telescope (COMPTEL) on CGRO, the X-Ray/Gamma-Ray Spectrometer (XGRS) on NEAR Shoemaker , the High Energy Transient Explorer (WMM and SXC), the Rossi X-ray Timing Explorer (PCA and ASM) and Ulysses .
The Fermi Gamma-ray Space Telescope, formerly called the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor, is being used to study gamma-ray bursts and solar flares.
The Compton Gamma Ray Observatory (CGRO) was a space observatory detecting photons with energies from 20 keV to 30 GeV, in Earth orbit from 1991 to 2000. The observatory featured four main telescopes in one spacecraft, covering X-rays and gamma rays, including various specialized sub-instruments and detectors. Following 14 years of effort, the observatory was launched from Space Shuttle Atlantis during STS-37 on April 5, 1991, and operated until its deorbit on June 4, 2000. It was deployed in low Earth orbit at 450 km (280 mi) to avoid the Van Allen radiation belt. It was the heaviest astrophysical payload ever flown at that time at 16,300 kilograms (35,900 lb).
Neil Gehrels Swift Observatory, previously called the Swift Gamma-Ray Burst Explorer, is a NASA three-telescope space observatory for studying gamma-ray bursts (GRBs) and monitoring the afterglow in X-ray, and UV/Visible light at the location of a burst. It was launched on 20 November 2004, aboard a Delta II launch vehicle. Headed by principal investigator Neil Gehrels until his death in February 2017, the mission was developed in a joint partnership between Goddard Space Flight Center (GSFC) and an international consortium from the United States, United Kingdom, and Italy. The mission is operated by Pennsylvania State University as part of NASA's Medium Explorer program (MIDEX).
The eSTAR project was a multi-agent system that aimed to implement a heterogeneous network of robotic telescopes for automated observing, and ground-based follow-up to transient events. The project is a joint collaboration between the Astrophysics Group of the University of Exeter and the Astrophysics Research Institute at Liverpool John Moores University. The project was led by Alasdair Allan and Tim Naylor at the University of Exeter, and Iain Steele at Liverpool John Moores University. The eSTAR Project was affiliated with the RoboNet Consortium, and the global Heterogeneous Telescope Networks Consortium.
BOOTES is a Global Network of Robotic Astronomical Observatories with seven sites located in Spain, New Zealand, China, Mexico, South Africa and Chile. While the BOOTES-1 station in Spain is devoted to wide-field astronomy, the additional stations include a similar setup : the 0.6m diameter robotic telescope, the EMCCD camera at the Cassegrain focus and the u'g'r'i'ZY filterset, which makes the BOOTES Network a unique resource for combining the data from all the instruments worldwide.
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 mirrors and instrumentation are suspended and its laser beam operates in a vacuum. The instrument's two arms are three kilometres long and located underground at the Kamioka Observatory which is near the Kamioka section of the city of Hida in Gifu Prefecture, Japan.
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 GRB in the sky is improved by increasing the spacing of the detectors, and also by more accurate timing of the reception. Typical spacecraft baselines of about one AU and time resolutions of tens of milliseconds can determine a burst location within several arcminutes, allowing follow-up observations with other telescopes.
VOEvent is a standardized language used to report observations of astronomical events; it was officially adopted in 2006 by the International Virtual Observatory Alliance (IVOA). Though most VOEvent messages currently issued are related to supernovae, gravitational microlensing, and gamma-ray bursts, they are intended to be general enough to describe all types of observations of astronomical events, including gravitational wave events. Messages are written in XML, providing a structured metadata description of both the observations and the inferences derived from those observations. The rapid dissemination of event data with a formalized language was the original impetus for the creation of VOEvents and the network used to transport the messages; indeed VOEvent messages are designed to be compact and quickly transmittable over the internet. The VOEvent language continues to evolve; the latest version is 2.0.
The Institute for Cosmic Ray Research (ICRR) of the University of Tokyo was established in 1976 for the study of cosmic rays.
High Energy Transient Explorer 2 was a NASA astronomical satellite with international participation. The satellite bus for the first HETE-1 was designed and built by AeroAstro, Inc. of Herndon, Virginia and was lost during launch on 4 November 1996; the replacement satellite, HETE-2 was built by Massachusetts Institute of Technology (MIT) based on the original HETE design.
The history of gamma-ray began with the serendipitous detection of a gamma-ray burst (GRB) on July 2, 1967, by the U.S. Vela satellites. After these satellites detected fifteen other GRBs, Ray Klebesadel of the Los Alamos National Laboratory published the first paper on the subject, Observations of Gamma-Ray Bursts of Cosmic Origin. As more and more research was done on these mysterious events, hundreds of models were developed in an attempt to explain their origins.
GRB 990123 is a gamma-ray burst which was detected on January 23, 1999. It was the first GRB for which a simultaneous optical flash was detected. Astronomers first managed to obtain a visible-light image of a GRB as it occurred on January 23, 1999, using the ROTSE-I telescope in Los Alamos, New Mexico. The ROTSE-I was operated by a team under Dr. Carl W. Akerlof of the University of Michigan and included members from Los Alamos National Laboratory and Lawrence Livermore National Laboratory. The robotic telescope was fully automated, responding to signals from NASA's BATSE instrument aboard the Compton Gamma Ray Observatory within seconds, without human intervention. In the dark hours of the morning of January 23, 1999, the Compton satellite recorded a gamma-ray burst that lasted for about a minute and a half. There was a peak of gamma and X-ray emission 25 seconds after the event was first detected, followed by a somewhat smaller peak 40 seconds after the beginning of the event. The emission then fizzled out in a series of small peaks over the next 50 seconds, and eight minutes after the event had faded to a hundredth of its maximum brightness. The burst was so strong that it ranked in the top 2% of all bursts detected.
GRB 991216, nicknamed the Beethoven Burst by Dr. Brad Schaefer of Yale University, was a gamma-ray burst observed on December 16, 1999, coinciding with the 229th anniversary of Ludwig van Beethoven's birth. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.
GRB 000131 was a gamma-ray burst (GRB) that was detected on 31 January 2000 at 14:59 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.
David Louis Band or David L. Band was an astronomer who studied the theory of gamma-ray bursts.
Gerald Jay (Jerry) Fishman is an American research astrophysicist, specializing in gamma-ray astronomy. His research interests also include space and nuclear instrumentation and radiation in space. A native of St. Louis, Missouri, Fishman obtained a B.S. with Honors degree in physics from the University of Missouri in 1965, followed by M.S. and Ph.D. degrees in space science from Rice University in 1968 and 1970, respectively.
A kilonova is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge. These mergers are thought to produce gamma-ray bursts and emit bright electromagnetic radiation, called "kilonovae", due to the radioactive decay of heavy r-process nuclei that are produced and ejected fairly isotropically during the merger process. The measured high sphericity of the kilonova AT2017gfo at early epochs was deduced from the blackbody nature of its spectrum.
Multi-messenger astronomy is astronomy based on the coordinated observation and interpretation of signals carried by disparate "messengers": electromagnetic radiation, gravitational waves, neutrinos, and cosmic rays. They are created by different astrophysical processes, and thus reveal different information about their sources.
GW 170817 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 17 August 2017, originating from the shell elliptical galaxy NGC 4993. The signal was produced by the last minutes of a binary pair of neutron stars' inspiral process, ending with a merger. It is the first GW observation that has been confirmed by non-gravitational means. Unlike the five previous GW detections, which were of merging black holes not expected to produce a detectable electromagnetic signal, the aftermath of this merger was also seen by 70 observatories on 7 continents and in space, across the electromagnetic spectrum, marking a significant breakthrough for multi-messenger astronomy. The discovery and subsequent observations of GW 170817 were given the Breakthrough of the Year award for 2017 by the journal Science.
PyCBC is an open source software package primarily written in the Python programming language which is designed for use in gravitational-wave astronomy and gravitational-wave data analysis. PyCBC contains modules for signal processing, FFT, matched filtering, gravitational waveform generation, among other tasks common in gravitational-wave data analysis.