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 Basque researchers turn light upside down
23.02.2018 | Elhuyar Fundazioa

nachricht Attoseconds break into atomic interior
23.02.2018 | Max-Planck-Institut für Quantenoptik

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: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>