GRB 050709
Encyclopedia
GRB 050709 was a gamma-ray burst (GRB) detected on July 9, 2005. A gamma-ray burst is a highly luminous
flash of gamma ray
s, the most energetic form of electromagnetic radiation
, which is often followed by a longer-lived "afterglow" emitting at longer wavelengths (X-ray
, ultraviolet
, optical, infrared
, and radio
).
A radio source was detected on July 11 at a position of R.A.
=, Decl.
=. Optical observations taken 34 hours after the burst revealed an optical afterglow. This was the first discovery of transient optical emission from a short burst.
were collimated into a jet with a half-angle greater than 6° and interacted with a high-density medium. In the second, the jet had a half-angle greater than 2° and interacted with a low-density medium. If the characteristics of the first model, which were similar to those of GRB 050724, are representative of all short GRBs, then the emission jets of short GRBs are less collimated and less energetic than those of long GRBs.
association, a common feature of long bursts. This suggested that short-duration bursts release much less energy than long-duration bursts.
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 of 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...
, which is often followed by a longer-lived "afterglow" emitting 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
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
).
Observations
GRB 050709 was detected by multiple instruments on board HETE-2 on June 9, 2005 at 22:36:37 UTC. The first pulse lasted 100 milliseconds, followed 30 seconds later by a fainter pulse lasting approximately 150 seconds. The disparity between the spectra of the first pulse and the second suggest that the second pulse was the onset of the burst's afterglow. As such, this burst was classified as a short-duration hard burst.A radio source was detected on July 11 at a position of R.A.
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:...
=, Decl.
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...
=. Optical observations taken 34 hours after the burst revealed an optical afterglow. This was the first discovery of transient optical emission from a short burst.
Ejecta
Analysis of the burst's afterglows suggested two models to explain the burst's afterglow. In the first, the burst's ejectaEjecta
Ejecta can mean:*In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor...
were collimated into a jet with a half-angle greater than 6° and interacted with a high-density medium. In the second, the jet had a half-angle greater than 2° and interacted with a low-density medium. If the characteristics of the first model, which were similar to those of GRB 050724, are representative of all short GRBs, then the emission jets of short GRBs are less collimated and less energetic than those of long GRBs.
Host galaxy
GRB 050709's x-ray afterglow associated the burst with a host galaxy at a redshift of z = 0.16. This galaxy's light curve excluded the possibility of a supernovaSupernova
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...
association, a common feature of long bursts. This suggested that short-duration bursts release much less energy than long-duration bursts.