GRB 980425
Encyclopedia
GRB 980425 was a gamma-ray burst (GRB) that was detected on 25 April 1998 at 21:49 UTC. A gamma-ray burst is a highly luminous
flash associated with an explosion in a distant galaxy and producing gamma ray
s, the most energetic form of electromagnetic radiation
, and often followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray
, ultraviolet
, optical, infrared
, and radio
). GRB 980425 occurred at approximately the same time as SN 1998bw
, providing the first evidence that gamma-ray bursts and supernova
e are related.
on 25 April 1998 at 21:49 UTC. The burst lasted approximately 30 seconds and had one peak in its light curve
. The Narrow Field Instruments (NFIs) onboard BeppoSAX began making observations of the region approximately 10 hours after the burst was detected. The NFIs detected two previously unknown x-ray sources—one at α
= , δ
= , and the other at α = , δ = . In the days that followed the burst, a variable
object was detected in the original BeppoSAX error box that was not coincident with either of the two X-ray sources. The object's light curve implied that it might be a supernova
.
and GRB 980425 were related. This was the first evidence of a physical relationship between gamma-ray bursts and supernovae. Evidence for this relationship and the details thereof continues to develop in the years since this breakthrough. Analyses of previously discovered bursts, such as GRB 970228
and GRB 980326, showed that they may have also been affected by supernovae.
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
flash associated with an explosion in a distant galaxy and producing gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s, the most energetic form of electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
, and often followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
, ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
, optical, infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
, and radio
Radio waves
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...
). GRB 980425 occurred at approximately the same time as SN 1998bw
SN 1998bw
SN 1998bw was a rare type I/Ib gamma ray supernova detected on 26 April 1998 in the ESO 184-G82 spiral galaxy, which some astronomers believe may be an example of a collapsar. The supernova has been linked to GRB 980425, which was detected on 25 April 1998, the first time a gamma-ray burst has...
, providing the first evidence that gamma-ray bursts and supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
e are related.
Observations
GRB 980425 was first detected by the Gamma-Ray Burst Monitor onboard BeppoSAXBeppoSAX
BeppoSAX was an Italian–Dutch satellite for X-ray astronomy which played a crucial role in resolving the origin of gamma-ray bursts , the most energetic events known in the universe...
on 25 April 1998 at 21:49 UTC. The burst lasted approximately 30 seconds and had one peak in its light curve
Light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...
. The Narrow Field Instruments (NFIs) onboard BeppoSAX began making observations of the region approximately 10 hours after the burst was detected. The NFIs detected two previously unknown x-ray sources—one at α
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
= , δ
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
= , and the other at α = , δ = . In the days that followed the burst, a variable
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
object was detected in the original BeppoSAX error box that was not coincident with either of the two X-ray sources. The object's light curve implied that it might be a supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
.
Supernova relation
A search for the burst's radio afterglow resulted in one object that was coincident with the previously discovered supernova candidate, giving early credence to the idea that SN 1998bwSN 1998bw
SN 1998bw was a rare type I/Ib gamma ray supernova detected on 26 April 1998 in the ESO 184-G82 spiral galaxy, which some astronomers believe may be an example of a collapsar. The supernova has been linked to GRB 980425, which was detected on 25 April 1998, the first time a gamma-ray burst has...
and GRB 980425 were related. This was the first evidence of a physical relationship between gamma-ray bursts and supernovae. Evidence for this relationship and the details thereof continues to develop in the years since this breakthrough. Analyses of previously discovered bursts, such as GRB 970228
GRB 970228
GRB 970228 was the first gamma-ray burst for which an afterglow was observed. 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 , but until this event, GRBs had only been observed in highly luminous bursts of...
and GRB 980326, showed that they may have also been affected by supernovae.