GRB 970228

GRB 970228

Event type	Gamma-ray burst
Date	c. 8.123 billion years ago (detected 28 February 1997, 02:58 UTC)
Duration	c. 1 minute and 20 seconds
Instrument	Fermi Gamma-ray Space Telescope
Constellation	Orion
Right ascension	05h 01m 46.7s
Declination	+11° 46′ 53.0″[1]
Epoch	J2000
Distance	c. 8.123 billion ly
Redshift	0.695
Total energy output	5.2×1044 J
Other designations	GRB 970228
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GRB 970228^[2] was the first gamma-ray burst (GRB) for which an afterglow was observed.^[3] 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 (in wavelengths such as radio waves, x-rays, and even visible light), but until this event, GRBs had only been observed in highly luminous bursts of high-energy gamma rays (the most energetic form of electromagnetic radiation); this resulted in large positional uncertainties which left their nature very unclear.

The burst had multiple peaks in its light curve and lasted approximately 80 seconds. Peculiarities in the light curve of GRB 970228 suggested that a supernova may have occurred as well. The position of the burst coincided with a galaxy about 8.1 billion light-years^[4] away (a redshift of z = 0.695), providing early evidence that GRBs occur well beyond the Milky Way; this was proven decisively two months later with a subsequent burst GRB 970508.