A soft gamma repeater (SGR) is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them.
History
On March 5, 1979 a powerful gamma-ray burst was noted. As a number of receivers at different locations in the Solar System saw the burst at slightly different times, its direction could be determined, and it was shown to originate from near a supernova remnant in the Large Magellanic Cloud.
{| class="wikitable"
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! Object !! Discovery !! Notes
|-
| SGR 0525−66 ||1979 ||
|-
| SGR 1806−20 ||1979/1986 ||The most powerful soft gamma repeater burst yet recorded was observed coming from this object on December 27, 2004.
|-
| SGR 1900+14 ||1979/1986 || 20,000 lyr away; powerful, affected the Earth's atmosphere.
|-
| SGR 1627−41 ||1998 ||
|-
| SGR J1550−5418 || 2008 || Rotates once every 2.07 seconds, holds the record for the fastest-spinning magnetar.
|-
| SGR 0501+4516 ||2008 || 15,000 lyr away; X-ray outburst detected by Swift satellite 22 August 2008.
|-
| SGR J1745−2900 || 2013 || A soft gamma repeater orbiting the black hole in Sagittarius A*.
|-
| SGR 1935+2154 || 2014 || 30,000 lyr away; First ever detected fast radio burst inside the Milky Way, and the first ever to be linked to a known source.
|}
The numbers give the position in the sky, for example, SGR 0525-66 has a right ascension of 5h25m and a declination of −66°. The date of discovery sometimes appears in a format such as 1979/1986 to refer to the year the object was discovered, in addition to the year soft gamma repeaters were recognized as a separate class of objects rather than "normal" gamma-ray bursts.
References
==Further reading== <!-- future refs -->
- On the persistent X-ray emission from the soft gamma-ray repeaters. Usov. 1996