George's Random Astronomical Object

Object 18: GRB 100206A

Podcast release date: 06 April 2020

Right ascension: 03:08:38.9

Declination: +13:09:26

Epoch: J2000

Constellation: Aires

Corresponding Earth location: The Gulf of Aden about 46 km off the coast of Yemen

The GRB in the name GRB 100206A stands for "Gamma Ray Burst". These are sources in the sky that briefly produce extremely huge amounts of gamma radiation over a single period of time that could be as short as a few milliseconds or as long as a few minutes. They were discovered in the late 1960s by American satellites designed to look for gamma radiation from nuclear bombs on Earth [1,2]. It wasn't until 1997, however, that these were identified as objects outside the Milky Way Galaxy. They are thought to be formed multiple ways. One of the phenomena that could form gamma ray bursts are the merger of two neutron stars or two black holes; these bursts should be shorter than 2 seconds [3]. Bursts larger than 2 seconds are thought to form primarily from supernovae [3].

GRB 100206A was detected at 1:30 pm Universal Time on February 6th, 2011, by the Swift and Fermi satellites, which were designed specifically for detecting gamma ray bursts [4]. The total length of the gamma ray burst was 0.2 seconds, which places it into the short burst category [4]. After its detection, a series of observatories around the world observed the burst in the near-infrared and visible parts of the electromagnetic spectrum to try to find the afterglow that should be produced by the burst at these wavelengths. It would be fun to name all the observatories that looked at this object, but then I don't think people want to listen to me read a list of observatories for several minutes. Besides this, none of the observatories could find the afterglow, which was a little bit of a let-down.

Despite this, a couple of the larger telescopes that tried to detect the afterglow in near-infrared and visible light were actually able to detect the galaxy that is most likely to be the host of the gamma ray burst [4], and the host galaxy turned out to be one of the most interesting thing about this object. Researchers also dug up archival mid-infrared, near-infrared, and visible light data and managed to detect the host galaxy in those data as well.

The galaxy appears to be a disk-like galaxy, which would mean that it is probably a spiral galaxy, and the galaxy is at a distance where we are seeing light emitted when the Universe was 4.5 billion years younger [4]. What is unusual, though, is that the host galaxy is a luminous infrared galaxy [4]. These are galaxies that produce infrared emission that is equivalent to somewhere between 100 billion and 1 trillion times the total amount of energy emitted by the Sun. The host galaxy for GRB 100206A, like other luminoius infrared galaxies, is forming stars at a very rapid pace; stars are forming about 10 times faster than in the Milky Way. The regions where stars form are surrounded by clouds of interstellar gas and dust, and the dust absorbs the ultraviolet and visible light from the stars in these regions and re-radiates the energy as infrared light, which is why the infrared brightness is so high. For comparison, most other short gamma ray bursts are found in galaxies with relatively wimpy star formation rates. The host galaxy also has a rather unusually high amount of elements heavier than hydrogen or helium, which implies that, for a very long time, the galaxy has been forming a lot of stars that can synthesize these elements. Nonetheless the gamma ray burst may not be associated with the younger stars in its host galaxy. Instead, the burst may have actually formed from two merging neutron stars or black holes that were intermixed in the very old stars on the outskirts of the galaxy [4].

A few more gamma ray burst have similar host galaxies, but its still rare to find a short gamma ray burst like GRB 100206A that is associated with a galaxy where stars are forming at a very rapid rate [5]. It just demonstrates that we shouldn't make too many assumptions about any specific type of astronomical phenomenon.


[1] Klebesadel, Ray W. et al., Observations of Gamma-Ray Bursts of Cosmic Origin, 1973, Astrophysical Journal Letters, 182, L85

[2] Robson, Colin, What are Gamma-Ray Bursts and how Did we Discover Them?, 2013, Futurism

[3] Berger, Edo, Short-Duration Gamma-Ray Bursts, 2014, Annual Reviews of Astronomy and Astrophysics, 52, 43

[4] Perley, D. A. et al., The Luminous Infrared Host Galaxy of Short-duration GRB 100206A, 2012, Astrophysical Journal, 758, 122

[5] Chrimes, Ashley A. et al., Investigating a population of infrared-bright gamma-ray burst host galaxies, 2018, Monthly Notices of the Royal Astronomical Society, 478, 2

Podcast and Website: George J. Bendo

Music: Immersion by Sascha Ende, which is distributed by under a Creative Commons 4.0 Attribution License

Sound Effects: alcoceba, Dalibor, ivolipa, jameswrowles, metrostock99, Samulis, sforsman, and Xulie at The Freesound Project

Image Viewer: Aladin Sky Atlas (developed at CDS, Strasbourg Observatory, France)


© George Bendo 2020. See the acknowledgments page for additional information.

Last update: 25 April 2020