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 A tale of two pulsars' tails: Plumes offer geometry lessons to astronomers
18.01.2017 | Penn State

nachricht Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie

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: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>