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 Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>