Soft gamma repeater

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A soft gamma repeater (SGR) is an

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.[1]

History

On March 5, 1979[2] a powerful gamma-ray burst was noted. As a number of receivers at different locations in the Solar System[3] 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.[2][3]

Over time it became clear that this was not a normal gamma-ray burst. The photons were less energetic in the soft gamma-ray and hard X-ray range, and repeated bursts came from the same region.

Astronomer

SGR 1806-20. The period had increased by 0.008 seconds since 1993, and she calculated that this would be explained by a magnetar with a magnetic-field strength of 8×1010 teslas (8×1014 gauss
). This was enough to convince the international astronomical community that soft gamma repeaters are indeed magnetars.

An unusually spectacular soft gamma repeater burst was

RXTE), an X-ray satellite
, received its strongest signal from this burst at this time, even though it was directed at a different part of the sky, and should normally have been shielded from the radiation.

List of SGR

Known soft gamma repeaters include:[4]

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[5] 2008 Rotates once every 2.07 seconds, holds the record for the fastest-spinning magnetar.
SGR 0501+4516[6] 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

  1. S2CID 14745312
    .
  2. ^ a b c d Duncan, Robert C. (May 1998). "The March 5th Event". Magnetars', Soft Gamma Repeaters & Very Strong Magnetic Fields. University of Texas at Austin. Retrieved March 2, 2009.
  3. ^ a b c d Dooling, Dave (May 20, 1998). ""Magnetar" discovery solves 19-year-old mystery". NASA. Archived from the original on March 11, 2009. Retrieved March 2, 2009.
  4. ^ "McGill SGR/AXP Online Catalog".
  5. ^ "Star Emits Intense Celestial Fireworks". Space.com. 10 February 2009.
  6. ^ "Giant eruption reveals 'dead' star". European Space Agency. 16 June 2009. Retrieved 28 December 2009.

Further reading

External links

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