Tag: GRB

Astronomers link fast X-ray bursts with gamma ray bursts and supernovae

1:17 pm

Using observations of a fast X-ray burst (FXT) 2.8 billion light years away by a plethora of space- and ground-based telescopes, astronomers now think the burst was caused by a massive star’s supernova explosion that would normally result in a gamma ray burst (GRB), but does not because the star’s outer layers trap the gamma rays from escaping.

Through analysis of EP 250108a’s rapidly evolving signal over the first six days following initial detection, the team found that this FXT is likely a ‘failed’ variation of a gamma-ray burst (GRB). GRBs are the most powerful explosions in the Universe and have been observed preceding supernovae. During these events, violent geysers of high-energy particles burst through a star’s outer layers as it collapses in on itself. These jets flow at nearly the speed of light and are detectable by their gamma-ray emission.

EP 250108a appears similar to a jet-driven explosion, but one in which the jets do not break through the outer layers of the dying star and instead remain trapped inside. As the stifled jets interact with the star’s outer layers, they decelerate and their kinetic energy is converted to the X-rays detected by Einstein Probe.

As always, there are many uncertainties with this conclusion.

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New gamma ray burst violates the explanations of scientists

9:04 am

The uncertainty of science: A newly discovered long gamma ray burst (GRB) that appears to have been formed by the merger of two neutron stars has contradicted the long held views of scientists as to the origin of this particular type of GRB.

Prior to the discovery of this burst, astronomers mostly thought that there were just two ways to produce a GRB. The collapse of a massive star just before it explodes in a supernova could make a long gamma-ray burst, lasting more than two seconds. Or a pair of dense stellar corpses called neutron stars could collide, merge and form a new black hole, releasing a short gamma-ray burst of two seconds or less.

But there had been some outliers. A surprisingly short GRB in 2020 seemed to come from a massive star’s implosion (SN: 8/2/21). And some long-duration GRBs dating back to 2006 lacked a supernova after the fact, raising questions about their origins. “We always knew there was an overlap,” says astrophysicist Chryssa Kouveliotou of George Washington University in Washington, D.C., who wrote the 1993 paper that introduced the two GRB categories, but was not involved in the new work. “There were some outliers which we did not know how to interpret.”

There’s no such mystery about GRB 211211A: The burst lasted more than 50 seconds and was clearly accompanied by a kilonova, the characteristic glow of new elements being forged after a neutron star smashup.

Kouveliotou’s claim is not how I remember things back in 1990s. Then, the astronomers seemed certain that the two GRB classes were entirely separate, with no overlap, despite the large number of uncertainties.

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Scientists puzzle over possible connection between a fast radio burst and a gamma ray burst

9:31 am

The uncertainty of science: In trying to explain the relatively new mystery of fast radio bursts (FRB), of which only about 20 have been detected and of which very little is known, scientists are intrigued by a gamma ray burst (GRB) that apparently occurred at the same time and place of one FRB.

Seeing the FRB event in a different wavelength would normally help astronomers better understand the FRB The problem is that this particular GRB only makes the mystery of FRBs more baffling.

One puzzle is that the two signals portray different pictures of the underlying source, which seems to be as much as 10 billion light years (3.2 gigaparsecs) away. Whereas the radio burst lasted just a few milliseconds, the γ-ray signal lasted between two and six minutes, and it released much more energy in total than the radio burst. “We’ve pumped up the energy budget more than a billion times,” says study co-author Derek Fox, an astrophysicist at Penn State.

This has big implications for the FRB’s origin. One leading theory suggests that FRBs are flares from distant magnetars — neutron stars with enormous magnetic fields that could generate short, energetic blasts of energy, and do so repeatedly, as at least one FRB is known to do. Although magnetars are thought to produce γ-rays, they would not emit such high energy and over such a long time, says Fox. “This is a severe challenge for magnetar models,” he says.

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Engineers have returned to full operation the x-ray instrument on the Swift gamma-ray burst space telescope.

11:58 pm

Engineers have returned to full operation the x-ray instrument on the Swift gamma-ray burst space telescope.

They are still investigating what went wrong this week, but have figured out how to get the instrument back in full automatic robotic mode so that it can gather x-ray data on gamma ray bursts within seconds of their occurence.

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Astronomers have found evidence which suggests that most of the universe’s gold was created during the collision and merger of two neutron stars.

8:54 am

Astronomers have found evidence which suggests that most of the universe’s gold was created during the collision and merger of two neutron stars.

A binary of two neutron stars will eventually spiral into each other. When they do, scientists believe that their violent merger produces short gamma ray bursts (GRB). Observations of a short GRB burst in June found a lot of spectroscopic evidence of gold.

[T]he explosion had been responsible for the creation of a whole menagerie of heavy elements. They estimated that an equivalent of 1% of the sun’s matter was being flung out from the collision in a tail, and about 10 parts per million of that tail was made of gold.

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Last Saturday the space telescope Swift detected the most powerful gamma ray bursts ever detected.

7:59 pm

Last Saturday the space telescope Swift detected the most powerful gamma ray burst ever detected.

You can see the raw reports of the detection, followed up immediately by a host of other ground-based and space-based observations at this website. Click on the circulars for GRB130427A, starting with circular 14448. When this happened last Saturday I was out camping. When I got home there were dozens of circulars to look at. Based on the data here, this gamma-ray burst was relatively close for a grb, approximately 3.6 billion light years away.

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