Register to reply

Gamma Ray Bursts

by |Glitch|
Tags: bursts, gamma
Share this thread:
|Glitch|
#1
Nov22-13, 11:25 PM
P: 54
I recently read the following article:
Brightest Explosion In the Universe Ever Seen Defies Astronomy Theories

A mysterious blast of light spotted earlier this year near the constellation Leo was actually the brightest gamma-ray burst ever recorded, and was triggered by an extremely powerful stellar explosion, new research reports.

Source: http://www.space.com/23684-brightest...mysteries.html
It was not very long, and it did not contain much information. However, after a little searching I discovered the article was referring to GRB 130427A.

The key features of this GRB are its strength at 94 GeV, and its duration at "better part of a day." Also its distance of 3.6 billion light years puts it relatively close by for a typical GRB.

While searching for more information on this particular event I also encountered this paper:
Detection of Pulsed Gamma Rays Above 100 GeV from the Crab Pulsar --- arXiv:1108.3797
They were detecting gamma ray pulses in the 200 to 400 GeV range. Furthermore, these GRB had to be at least 10 solar radii from the surface of the pulsar. Granted, pulsars are neutron stars with a radius of maybe a dozen miles. So at 10 solar radii we are not talking about a large distance. Also, the Crab Nebula is only 6,500 ± 1600 light years, which is considerably closer than 3.6 billion light years.

Is it the strength and the distance of the GRB that determines its power? In other words, if GRB 130427A were measured from a distance of 6,500 ± 1600 light years, instead of 3.6 billion light years, would the power of the GRB be significantly larger than the gamma ray pulses of 400 GeV being detected in the Crab Nebula?
Phys.Org News Partner Astronomy news on Phys.org
Spitzer telescope witnesses asteroid smashup
Radio telescopes settle controversy over distance to Pleiades
Integral gamma-ray observatory demonstrates white dwarfs can reignite and explode as supernovae
Drakkith
#2
Nov22-13, 11:32 PM
Mentor
Drakkith's Avatar
P: 11,874
I'm not sure. At 3.6 billion light years the gamma rays have probably been stretched somewhat by expansion but I'm not sure how far, nor do I know whether the 94 GeV was before or after the effects of expansion.

Also, note that the given energies are per photon, not the power output of the event.
|Glitch|
#3
Nov23-13, 12:01 AM
P: 54
Quote Quote by Drakkith View Post
I'm not sure. At 3.6 billion light years the gamma rays have probably been stretched somewhat by expansion but I'm not sure how far, nor do I know whether the 94 GeV was before or after the effects of expansion.

Also, note that the given energies are per photon, not the power output of the event.
I guess that is what I am asking. They are saying not only was it the biggest GRB by more than a factor of three, but also incredibly long, lasting several hours. Could even the largest, most massive stars, like R136a, produce such an event?

As you say, the energies per photon they are receiving was measuring 94 GeV. Yet we are also detecting gamma rays from the Crab Pulsar measuring 200 to 400 GeV. Granted, they are two completely different mechanisms, and the Crab Pulsar are short GRBs, only miliseconds in duration. But three times stronger than the biggest recorded GRB? You can understand my confusion.

The only way I could figure out the discrepancy was due to distance.

Drakkith
#4
Nov23-13, 01:36 AM
Mentor
Drakkith's Avatar
P: 11,874
Gamma Ray Bursts

I can definitely tell you that the total energy output from GRB 130427A was MUCH more than anything from the Crab Nebula. Had it been 6,000 light years away instead of 3.6 billion it would have been unimaginably bright.

Note that the 200 - 400 GeV gamma rays from the Crab Nebula were not detected by the LAT aboard the Fermi Space Telescope. The "3 times greater" refers to the energy of the gamma rays detected by the LAT. One of the gamma rays it detected had an energy 3 times higher than the previous record for the LAT, not three times higher than ever detected.
|Glitch|
#5
Nov26-13, 02:42 PM
P: 54
There is more information about this particular event.
Birth of black hole witnessed, marking watershed moment for astronomy

The virtual impossibility of observational astronomy has never been clearer. With astronomers having recorded so many events, now that they’ve used so many different instruments to wring all possible insight from what little information somehow makes it all the way to Earth, simply pointing telescopes at stars is providing diminishing returns. To keep moving forward we need to make use of the universe’s most unusual and, in many cases, violent events so we can see some truly novel data. It’s not just a matter of patience, since the the space industry can’t possibly set up enough telescopes to look everywhere at once. With so much depth through which to zoom, it would seem a lost cause to try to capture unexpected, short-lived events.

And yet, this week a momentous event occurred somewhere in the universe, now dubbed GRB 130427A, and an “armada of instruments” from all over the world saw it produce a gamma ray burst more powerful than what many researchers believed theoretically possible. Now thought to be the collapse of a giant star and the birth of a black hole, the event has been described as a “Rosetta stone moment” for astronomy. It has sent out information astronomers will be studying for many years to come, and while it’s too soon to draw any real conclusions, there is already widespread excitement about the sheer newness of it.

Source: http://www.extremetech.com/extreme/1...-for-astronomy
I was under the impression that all long-duration (more than two seconds) gamma-ray bursts were the result of either a hypernovae or a pair-instability supernovae. While the result of a hypernovae results in a black-hole, the result of a pair-instability supernovae leaves no black hole, or remnants of any kind.

GRB 130427A lasted 80 seconds, with an after-glow that lasted for hours ("better part of a day"). Therefore, how can they make a definitive statement about the birth of a black hole? Why would this long-duration GRB produce a black hole and not all the other long-duration GRBs we have previously detected, making it a "watershed moment?"

Furthermore, since GRB 130427A was one of the five closest GRBs detected (at ~3.6 billion light years distant), would they not also be able to detect the remnants of a hypernovae or a pair-instability supernovae that caused the GRB?

One of the things that does make GRB 130427A unique is the number of instruments we had observing the event:
  • Los Alamos' RAPTOR (RAPid Telescopes for Optical Response)
  • NASA's Fermi Gamma-Ray Space Telescope
  • NASA's NuSTAR Space Telescope
  • NASA's Swift Gamma-Ray Burst Space Telescope


Optical Flash From GRB 130427A by the RAPTOR Telescopes
OmCheeto
#6
Nov26-13, 05:18 PM
PF Gold
OmCheeto's Avatar
P: 1,431
Quote Quote by |Glitch| View Post
There is more information about this particular event.
I was under the impression that all long-duration (more than two seconds) gamma-ray bursts were the result of either a hypernovae or a pair-instability supernovae. While the result of a hypernovae results in a black-hole, the result of a pair-instability supernovae leaves no black hole, or remnants of any kind.

GRB 130427A lasted 80 seconds, with an after-glow that lasted for hours ("better part of a day"). Therefore, how can they make a definitive statement about the birth of a black hole? Why would this long-duration GRB produce a black hole and not all the other long-duration GRBs we have previously detected, making it a "watershed moment?"

Furthermore, since GRB 130427A was one of the five closest GRBs detected (at ~3.6 billion light years distant), would they not also be able to detect the remnants of a hypernovae or a pair-instability supernovae that caused the GRB?

One of the things that does make GRB 130427A unique is the number of instruments we had observing the event:
  • Los Alamos' RAPTOR (RAPid Telescopes for Optical Response)
  • NASA's Fermi Gamma-Ray Space Telescope
  • NASA's NuSTAR Space Telescope
  • NASA's Swift Gamma-Ray Burst Space Telescope


Optical Flash From GRB 130427A by the RAPTOR Telescopes
I wish the author(a "writer" with a BSc in Molecular Biology?) had listed some references.

The comments regarding the article are quite entertaining.

Quote Quote by chojin999
That proves nothing. No one knows what that object could be.. there could be aliens moving giant stars and planets ... this proves absolutely nothing.
2 likes 7 dislikes

Quote Quote by Yoduh99
Seems like a reasonable alternative hypothesis.
16 likes, 1 dislike
ps. I know nothing of Cosmology, but saw a headline about GRB 130427A the other day, that made it sound like an exciting event.

Headlines also tune me in to current events, which generally lead me to ask; "What the hell is a Raptor"?, which leads to googling, which leads to articles:

Quote Quote by science20.com
GRB 130427A: Black Hole Birth Captured By RAPTOR

Los Alamos National Laboratory astrophysicist Tom Vestrand poses with a telescope array that is part of the RAPTOR (RAPid Telescopes for Optical Response) system. RAPTOR is an intelligent visual system that scans the skies for optical anomalies and zeroes in on them when it detects them. This unique capability allowed the system to witness the rare birth of a black hole in the constellation Leo recently. Credit: Los Alamos National Laboratory
Which gave references.....

Quote Quote by LANL
Black hole birth captured by cosmic voyeurs

The RAPTOR system is a network of small robotic observatories that scan the skies for optical anomalies such as flashes emanating from a star in its death throes as it collapses and becomes a black hole.
Bingo!

So then, this layman wants to know the expert's opinions on whether or not our robotic eyes witnessed the birth of a black hole back on April 27th.
SteamKing
#7
Nov26-13, 07:42 PM
Emeritus
Sci Advisor
HW Helper
Thanks
PF Gold
P: 6,529
It has been hypothesized that a GRB emanating from within the Milky Way and pointing toward the Earth could cause an extinction-level event. This article reports that scientists think such an event has already occurred at least once before:

http://news.nationalgeographic.com/n...xtinction.html
|Glitch|
#8
Nov27-13, 09:11 AM
P: 54
Quote Quote by SteamKing View Post
It has been hypothesized that a GRB emanating from within the Milky Way and pointing toward the Earth could cause an extinction-level event. This article reports that scientists think such an event has already occurred at least once before:

http://news.nationalgeographic.com/n...xtinction.html
I have read that before. Some have speculated that the Ordovician-Silurian extinction was caused by such an event. There is also evidence to suggest Earth was hit by a gamma-ray burst from within the Milky Way much more recently.

Earth Was Hit by a Massive Gamma-Ray Burst in the Year 775


Register to reply

Related Discussions
Why Do We See So Many Gamma Ray Bursts? Astronomy & Astrophysics 8
Gamma Ray Bursts Astronomy & Astrophysics 5
Gamma Ray Bursts Cosmology 1
Gamma ray bursts! Astronomy & Astrophysics 6
Gamma bursts Astronomy & Astrophysics 13