GRB 101225A
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GRB 101225A, also known as the "Christmas burst", was a cosmic explosion first detected by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
's
Swift observatory 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 o ...
on Christmas Day 2010. The
gamma-ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nucleus, atomic nuclei. It consists of the shortest wavelength electromagnetic wav ...
emission lasted at least 28 minutes, which is unusually long. Follow-up observations of the burst's afterglow by the
Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
and ground-based observatories were unable to determine the object's distance using spectroscopic methods. In papers published in the journal ''
Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'', two different groups of astronomers proposed different theories about the event's origin. Sergio Campana's group proposes that the event was caused by a
comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
crashing onto a
neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
within our own galaxy. Christina Thöne's group prefers a more conventional
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
mechanism, involving a merger between a helium star and a
neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
at a distance of about 5.5 billion light years from Earth.


Observations

The
gamma ray burst In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milli ...
, in the constellation Andromeda, was first detected by the NASA
Swift Gamma-Ray Burst Mission 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 o ...
at 18:38 UT on December 25, 2010. The gamma-ray emission had a duration of at least 28 minutes, which is unusually long. After news of the gamma-ray burst was sent to other observatories, the longer-wavelength "afterglow" of the burst was monitored by on-ground observatories and the Hubble Space Telescope. After the unusually long duration of gamma emissions,
x-ray emission Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays. Several types of astrophysical objects emit X-rays. They include galaxy clusters, black holes in active galactic nuclei (AGN), ...
s in the afterglow continued for just two days, an unusually short duration for this phase. Optical emissions observed over the first 10 days were characterized as those of "an expanding, cooling blackbody with a large initial radius". A faint light source appeared about 10 days after the burst and reached its maximum brightness 30 days after its appearance; observers described this light source as looking like a supernova. On January 6, 2011, the 10m Keck-I telescope equipped with the Low Resolution Imaging Spectrometer (LRIS) conducted
spectroscopic Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wav ...
measurements of the host galaxy of GRB 101225A. A 900s spectrum was obtained; it consisted of blue and red channels, covering the wavelength ranges ~320–550 nm and ~500–820 nm, respectively. Isotropic energy was estimated at (7.8 ± 1.6)
erg The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...
from the
Burst Alert Telescope 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 o ...
(BAT) data. The unusual characteristics of the afterglow led astronomers to generate novel hypotheses to explain the event. Observers were unable to ascertain the burst's distance from Earth, and the two alternative hypotheses of its origin place the event at radically different distances.


Hypotheses

Christina Thöne, of the Institute of Astrophysics of Andalusia in Spain, was lead author of a paper that proposed that the burst occurred in a binary system where a
neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
orbited a normal helium star that had just entered its
red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...
phase, which had enormously expanded its outer atmosphere. During the expansion, the red giant star engulfed the neutron star, resulting in both the ejection of the giant's atmosphere and rapid tightening of the neutron star's orbit. Once the two stars became wrapped in a common envelope of gas, the neutron star may have merged with the giant's core after just five orbits, or about 18 months. The end result of the merger was the birth of a
black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
or a
magnetar A magnetar is a type of neutron star with an extremely powerful magnetic field (∼109 to 1011 T, ∼1013 to 1015 G). The magnetic-field decay powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays.War ...
and the production of oppositely directed jets of particles moving at nearly the speed of light, followed by a weak
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
. The particle jets produced gamma rays. Jet interactions with gas ejected before the merger explain much of the burst's different nature. Based on this interpretation, the event took place about 5.5 billion
light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away (
redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in f ...
0.33), and the team has detected what may be a faint galaxy at the right location. An alternative hypothesis, offered by a team led by Sergio Campana of the
Brera Astronomical Observatory The Brera Observatory ( it, Osservatorio Astronomico di Brera) is an astronomical observatory in the Brera district of Milan, Italy. It was built in the historic Palazzo Brera in 1764 by the Jesuit astronomer Roger Boscovich. Following the suppre ...
(
INAF The National Institute for Astrophysics ( it, Istituto Nazionale di Astrofisica, or INAF) is an Italian research institute in astronomy and astrophysics, founded in 1999. INAF funds and operates twenty separate research facilities, which in turn e ...
), proposes that GRB 101225A was produced by a comet-like object that fell into a neutron star located in our own galaxy, only some 10,000 light-years from Earth. In this model, the comet-like object falls onto the neutron star and is disrupted by tidal forces. Hard
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
emission (the burst) results from the first matter falling onto the neutron star. X-ray emission and initial variations detected by Swift are attributed to clumps of material striking the star as the disc formed around it. Then the disk cools down and emits only at UV and optical wavelengths. More recently, at the 2013 Huntsville Gamma-ray Burst Symposium, several scientists proposed that GRB 101225A, along with GRB 111209A and 121027A are part of a new class of gamma ray bursts, termed ultra-long bursts and caused by the collapse of low metallicity blue supergiant stars. Andrew Levan and his colleagues used the Gemini North Telescope to determine that GRB 101225A was 7 billion light years distant much further than original estimates. This greater distance gives it a much higher energy level, which combined with longer duration and an absence of a supernova signature have led scientists, such as Bruce Gendre to suggest that these ultra-long bursts are the result of collapsing blue supergiant stars.


Significance

Astrophysicist Sergio Campana told
Space.com Space.com is an online publication focused on space exploration, astronomy, skywatching and entertainment, with editorial teams based in the United States and United Kingdom. The website offers live coverage of space missions, astronomical discov ...
that he thinks this was "the discovery of a completely new astrophysical phenomenon that adnot been envisaged before." He also said, "If tidal disruption of minor bodies around neutron stars is really happening", this event would not be "unique". Christina Thöne has said, "What the Christmas burst seems to be telling us is that the family of gamma-ray bursts is more diverse than we fully appreciate."


References

*


External links

* NASA
"Swift Observation of GRB 101225"
– GCN Report 314.1 ; J. L. Racusin et al. ; 17 January 2011 ; * NASA
"Trigger 441015: Swift detection of a possible burst or transient"
– GCN CIRCULAR 11493 ; Judith Racusin ; 25 December 2010 ; * UK Swift Science Data Centre
"The Christmas 2010 Burst"
Kim Page, 5 December 2011 ; {{Andromeda (constellation) 101225A 20101225 Articles containing video clips December 2010 events Andromeda (constellation)