Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists detect first afterglow of short gamma-ray bursts

19.02.2002


In the powerful, fast-fading realm of gamma-ray bursts, scientists say they have detected for the first time a lingering afterglow of the shortest types of bursts, which themselves disappear within a second.



This afterglow, radiating in X rays, may provide crucial insight into what triggers the mysterious bursts, the most energetic explosions in the Universe, second only to the big bang in total power. Previously, scientists had only detected the afterglow of longer bursts, which can last from a few seconds to about a minute and which seem to be of different origin than short bursts.

Davide Lazzati and Enrico Ramirez-Ruiz of the Institute of Astronomy at the University of Cambridge, along with Gabriele Ghisellini of the Osservatorio Astronomico di Brera in Merate, Italy, published these results in a recent issue of Astronomy & Astrophysics.


"The discovery of afterglows for long bursts in 1997 was a breakthrough, allowing us to determine that these explosions originate at cosmological distances, billions of light years away," said Lazzati. "Short bursts, which sometimes last for only a few milliseconds, are naturally harder to catch. With the discovery that they too have an afterglow, we may now finally have at least a small handle to study them."

Many scientists believe that longer bursts are from the collapse of massive stars. This is the so-called collapsar model, which may entail the collapse of a theorized hyperstar, more massive than the stars that explode as supernovae. Shorter bursts, under two seconds long, may originate from the collision of two neutron stars or black holes. As exotic as they may sound, gamma-ray bursts are remarkably common, detected nearly daily by earth-orbiting satellites.

Precious little is known about short bursts. Because they fade so quickly, orbiting burst detectors have been unable to accurately determine the location of the short bursts. Thus scientists cannot study the "crime scene" to search for clues of the explosion, as they can with longer bursts. Also, short bursts might not produce bright afterglows, further complicating their study.

The afterglow of any gamma-ray burst is caused by an event different from the original explosion, likely by blast waves from the burst ramming material from its chaotic source into matter in the surrounding medium. The detection of afterglows in short bursts may allow scientists to study the critical early phases of this phenomenon, hidden under the brighter prompt emission of long bursts.

Lazzati and his colleagues looked for signs of an afterglow in the archived data of short bursts detected by the BATSE instrument aboard NASA`s Compton Gamma-Ray Observatory, a mission that ran from 1991 to 1999. Although a given burst may only last a few seconds, each burst usually triggers the BATSE detectors to collect any gamma rays or higher-energy X rays (also called hard X rays or soft gamma rays) that come their way for the next 200-plus seconds.

The team studied several hundred short bursts lasting less than one second and having a high "signal-to-noise ratio," meaning that an afterglow would be less likely to be masked, or missed, by background radiation, or noise. The detection was performed on the sum of the best 76 light curves, since the afterglow of a single event is too faint to be detected against the background radiation.

"Characteristics in the light suggest that this peak in emission is produced by the deceleration of a relativistic blast wave, as predicted by the afterglow model and observed for the class of long-duration bursts," said Ramirez-Ruiz.

The similarity of afterglows does not rule out that short and long bursts are different, Ramirez-Ruiz said. Further analysis and observations, along with theoretical modeling, will be needed to determine the physics of the sources and their distance (perhaps within our Galaxy or from the distant, early Universe). While both types of bursts appear to emanate from their source as beamed jets, as opposed to an expanding fireball, the data indicate that short bursts may have an opening jet angle 3-10 times larger than the long bursts. Thus, they may have a similar overall energy, only spread out over a wider distance.

The afterglow phenomenon was first detected by the Italian-led Beppo-SAX X-ray satellite, nearly five years ago. The Swift satellite -- a NASA-led international mission on schedule for a 2003 launch -- will be "swift" enough to detect and localize short gamma-ray bursts and notify other satellites and telescopes within seconds. Swift`s X-ray and ultraviolet telescopes will also be able to study the afterglow phenomenon in depth.

Dr Davide Lazzate | alphagalileo
Further information:
http://www.ast.cam.ac.uk/~lazzati/short/short.html

More articles from Physics and Astronomy:

nachricht Mars 2020 mission to use smart methods to seek signs of past life
17.08.2017 | Goldschmidt Conference

nachricht Gold shines through properties of nano biosensors
17.08.2017 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>