* Astronomy

Blobrana · L

GRB 090423

Blobrana · L

Astronomers have spotted a burst of energy from a dying star, setting a record for the oldest and most distant object seen by Earth yet.
The 10-second blast was from when the universe was only 630 million years old.

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Blobrana · L

Long-Lag Gamma-Ray Bursts

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GRB 080916C

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RE: Gamma-Ray Bursts

Blobrana · L

An Australian team has marked the beginning of the International Year of Astronomy by revealing its discovery of the death of a star and the birth of a black hole.
The huge gamma ray burst was the most distant event ever seen from Western Australia, and one of the most distant seen from the nation as a whole.
The Australian team was the first in the world to see it, but then disaster struck when a computer crash meant the team's sophisticated astronomy camera stopped working.
The Zadko telescope, north of Perth, captured an image of a explosion that occurred about 11 billion years ago.
Dr David Coward told ABC Radio's AM the explosion resulted from the explosion of a massive star about 100 times bigger than our sun.

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Blobrana · L

These explosions, called gamma ray bursts (GRBs), are by far the brightest and most energetic phenomena in the known universe, second only to the Big Bang itself. Scientists were at a loss to imagine what could possibly cause them.
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Gamma-ray bursts, powerful glares of high-energy that wash through the Universe once every day or so are, for a brief time, the brightest objects in the gamma-ray sky. ESAs Integral gamma-ray observatory has observed several low-luminosity gamma-ray bursts, confirming the existence of an entire population of weaker bursts hardly noticed so far.
When it comes to detecting gamma-ray bursts (or GRBs), Integral is equipped with the most sensitive detector ever launched into space the IBIS imager. Its field of view is very well shielded from any background radiation, making the detection of faint gamma-ray signals possible.

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Title: Flares in Gamma Ray Bursts (II)
Authors: G. Chincarini, R. Margutti, J. Mao, F. Pasotti, C. Guidorzi, S. Covino, P. D'avanzo

We illustrate some of the preliminary results obtained with a new sample of flares and a new analysis. In these proceedings we deal mainly with the analysis related to the flare energy and describe the work in progress to measure the average flare luminosity curve. We discuss in brief GRB050904 and GRB050724 for matters relevant to this work. In particular we measure the contribution given to the flares by GRB050904 and give a new interpretation for the decaying early XRT light curve of GRB050724. We briefly illustrate the first evidence that the early decay is given by the subsequent emission of events with Width/TPeak < 1 and the total energy of these events is larger than the energy emitted during the prompt emission spike showing, indeed, that not only the central engine may still be active after hundreds of seconds of the first spike but that this may still be part of the prompt emission.

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Blobrana · L

A new study casts doubt on a long-standing belief about the power behind gamma-ray bursts, the most energetic explosions in the universe.
Researchers have found that short gamma-ray bursts—those that last a couple of seconds or less—have brighter afterglows than the simple, reigning model of afterglow emission predicts.
Gamma-ray bursts (GRBs) are believed to occur when a star that has collapsed into a black hole or a neutron star whips a disk of gas and dust into a pair of powerful jets moving at nearly light speed.
Like a lighthouse in fog, these so-called relativistic jets should cause whatever gas and dust that enshrouds the GRB source to glow brightly for hours after the burst's initial flash of energy.
Long gamma-ray bursts, which flash for up to 100 seconds or longer, are believed to occur when massive stars explode as supernovae. Such dying stars have plenty of debris around them, resulting in a bright afterglow.
But short bursts form in older galaxies where such supernovae are far less common. Instead, researchers believe a more likely progenitor is a pair of neutron stars that merge into one.

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