In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies, being the brightest and most extreme explosive events in the entire universe, as NASA describes the bursts as the "most powerful class of explosions in the universe". They are the most energetic and luminous electromagnetic events since the Big Bang. Gamma-ray bursts can last from ten milliseconds to several hours. After the initial flash of gamma rays, an "afterglow" is emitted, which is longer lived and usually emitted at longer wavelengths.
A stellar black hole is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. They are the remnants of supernova explosions, which may be observed as a type of gamma ray burst. These black holes are also referred to as collapsars.
Siding Spring Observatory near Coonabarabran, New South Wales, Australia, part of the Research School of Astronomy & Astrophysics (RSAA) at the Australian National University (ANU), incorporates the Anglo-Australian Telescope along with a collection of other telescopes owned by the Australian National University, the University of New South Wales, and other institutions. The observatory is situated 1,165 metres (3,822 ft) above sea level in the Warrumbungle National Park on Mount Woorat, also known as Siding Spring Mountain. Siding Spring Observatory is owned by the Australian National University (ANU) and is part of the Mount Stromlo and Siding Spring Observatories research school.
Roque de los Muchachos Observatory is an astronomical observatory located in the municipality of Garafía on the island of La Palma in the Canary Islands, Spain. The observatory site is operated by the Instituto de Astrofísica de Canarias, based on nearby Tenerife. ORM is part of the European Northern Observatory.
GRB 970228 was the first gamma-ray burst (GRB) for which an afterglow was observed. It was detected on 28 February 1997 at 02:58 UTC. Since 1993, physicists had predicted GRBs to be followed by a lower-energy afterglow, but until this event, GRBs had only been observed in highly luminous bursts of high-energy gamma rays ; this resulted in large positional uncertainties which left their nature very unclear.
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 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. 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.
The Virgo interferometer is a large-scale experiment for detecting gravitational waves. It is in Santo Stefano a Macerata, near the city of Pisa, Italy. The instrument – a Michelson interferometer – has two arms that are 3 kilometres (1.9 mi) long and contain its mirrors and instrumentation in an ultra-high vacuum.
HM Cancri (also known as HM Cnc or RX J0806.3+1527) is a binary star system about 1,600 light-years (490 pc; 1.5×1016 km) away. It comprises two dense white dwarfs orbiting each other once every 5.4 minutes, at an estimated distance of only 80,000 kilometres (50,000 miles) apart (about 1/5 the distance between the Earth and the Moon). The two stars orbit each other at speeds in excess of 400 kilometres per second (890,000 mph). The stars are estimated to be about half as massive as the Sun. Like typical white dwarfs, they are extremely dense, being composed of degenerate matter, and so have radii on the order of the Earth's radius. Astronomers believe that the two stars will eventually merge, based on data from many X-ray satellites, such as Chandra X-Ray Observatory, XMM-Newton and the Swift Gamma-Ray Burst Mission. These data show that the orbital period of the two stars is steadily decreasing at a rate of 1.2 milliseconds per year as they thus are getting closer by approximately 60 centimetres (2.0 ft) per day. At this rate, they can be expected to merge in approximately 340,000 years. With a revolution period of 5.4 minutes, HM Cancri is the shortest orbital period binary white dwarf system currently known.
Nial Rahil Tanvir is a British astronomer at the University of Leicester. His research specialisms are the Extragalactic distance scale, Galaxy evolution and Gamma ray bursts. Tanvir has featured in various TV programs, including The Sky at Night hosted by Sir Patrick Moore, and Horizon
GRB 970508 was a gamma-ray burst (GRB) detected on May 8, 1997, at 21:42 UTC; it is historically important as the second GRB with a detected afterglow at other wavelengths, the first to have a direct redshift measurement of the afterglow, and the first to be detected at radio wavelengths.
GRB 101225A, also known as the "Christmas burst", was a cosmic explosion first detected by NASA's Swift observatory on Christmas Day 2010. The gamma-ray emission lasted at least 28 minutes, which is unusually long. Follow-up observations of the burst's afterglow by the Hubble Space Telescope and ground-based observatories were unable to determine the object's distance using spectroscopic methods.
A neutron star merger is the stellar collision of neutron stars. When two neutron stars fall into mutual orbit, they gradually spiral inward due to the loss of energy emitted as gravitational radiation. When they finally meet, their merger leads to the formation of either a more massive neutron star, or—if the mass of the remnant exceeds the Tolman–Oppenheimer–Volkoff limit—a black hole. The merger can create a magnetic field that is trillions of times stronger than that of Earth in a matter of one or two milliseconds. These events are believed to create short gamma-ray bursts.
Time-domain astronomy is the study of how astronomical objects change with time. Said to have begun with Galileo's Letters on Sunspots, the field has now naturally expanded to encompass variable objects beyond the Solar System. Temporal variation may originate from movement of the source or changes in the object itself. Common targets include novae, supernovae, pulsating stars, flare stars, blazars and active galactic nuclei. Visible light time domain studies include OGLE, HAT-South, PanSTARRS, SkyMapper, ASAS, WASP, CRTS, GOTO and in a near future the LSST at the Vera C. Rubin Observatory.
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.
BlackGEM is an under-construction array of optical telescopes located at the La Silla astronomical observatory in Chile. This system is specifically designed to detect the optical counterparts from gravitational wave sources detected with Virgo and LIGO. Principal investigator of the array is Paul Groot.
GW170817 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, about 140 million light years away. The signal was produced by the last moments of the inspiral process of a binary pair of neutron stars, ending with their merger. It was the first GW observation to be confirmed by non-gravitational means. Unlike the five previous GW detections—which were of merging black holes and thus not expected to produce a detectable electromagnetic signal—the aftermath of this merger was seen across the electromagnetic spectrum by 70 observatories on 7 continents and in space, marking a significant breakthrough for multi-messenger astronomy. The discovery and subsequent observations of GW170817 were given the Breakthrough of the Year award for 2017 by the journal Science.
NGC 4993 is a lenticular galaxy located about 140 million light-years away in the constellation Hydra. It was discovered on 26 March 1789 by William Herschel and is a member of the NGC 4993 Group.
SN 2018cow was a very powerful astronomical explosion, 10–100 times brighter than a normal supernova, spatially coincident with galaxy CGCG 137-068, approximately 200 million ly (60 million pc) distant in the Hercules constellation. It was discovered on 16 June 2018 by the ATLAS-HKO telescope, and had generated significant interest among astronomers throughout the world. Later, on 10 July 2018, and after AT 2018cow had significantly faded, astronomers, based on follow-up studies with the Nordic Optical Telescope (NOT), formally described AT 2018cow as SN 2018cow, a type Ib supernova, showing an "unprecedented spectrum for a supernova of this class"; although others, mostly at first but also more recently, have referred to it as a type Ic-BL supernova. An explanation to help better understand the unique features of AT 2018cow has been presented. AT2018cow is one of the few reported Fast Blue Optical Transients (FBOTs) observed in the Universe. In May 2020, however, a much more powerful FBOT than AT 2018cow was reportedly observed.
MASTER is a International network of Russian fully robotic telescopes in five Russian sites, and in South Africa, Argentina,Mexica and the Canary Islands.
