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LIGO, High Gear Science Run
PFK
post Feb 11 2016, 07:08 PM
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QUOTE (hendric @ Feb 11 2016, 07:36 PM) *
Nice article about the post-doc who was monitoring when the event occurred:

http://www.sciencemag.org/news/2016/02/her...itational-waves


Great stuff. "He reached only one of the facilities—“Livingston, I think,” he says—but was told all was normal".
If only his words were "Livingston, I presume" smile.gif
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Mongo
post Feb 12 2016, 08:22 PM
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An interesting possible second binary black hole merger, from GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

QUOTE
The second most significant candidate event in the observation period (referred to as LVT151012) was reported on October 12, 2015 at 09:54:43 UTC with a combined matched filter SNR of 9:6. The search reported a false alarm rate of 1 per 2.3 years and a corresponding false alarm probability of 0.02 for this candidate event. Detector characterization studies have not identified an instrumental or environmental artifact as causing this candidate event. However, its false alarm probability is not sufficiently low to confidently claim this candidate event as a signal. Detailed waveform analysis of this candidate event indicates that it is also a binary black hole merger with source frame masses 23 M Sun and 13 MSun , if it is of astrophysical origin.

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TheAnt
post Jun 20 2016, 03:48 PM
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Now that a second black hole merger have been detected with high confidence. The idea that such events might be common have surfaced and made some think in radically new lines to explain how such events might happen quite often.
One hypothesis is that black holes and stars in the central part of globular clusters might collect in a 'Mosh pit' - I have a hunch that one of the team must be a metalhead for that expression to be used - indeed is a good term to describe the chaotic conditions and collisions that can occur in such a volume of space where stars and black holes are comparably tightly packed together.
Northwestern univ summary, video and link to the actual paper.
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moustifouette
post Oct 17 2017, 07:19 AM
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First merger of neutron stars detected and observed both with gravity waves and electromagnetical ones.

ligo press release
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JRehling
post Oct 18 2017, 10:25 PM
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The neutron star merger is actually bigger news than the black hole mergers, as it just provided the explanation for how half the elements on the periodic table are created, and provided absolute confirmation of how some gamma ray bursts are generated, while establishing with certainty that the speed of gravity and the speed of light are equal. Wow! That's a lot of science from one event!

I'm eager to see more neutron star mergers to provide information on the base rates of such events. And incidentally, I might be able to photograph one of these in the northern skies someday.
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Explorer1
post Oct 19 2017, 12:43 AM
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Incredible find!
I was under the impression that supernovas also create the elements heavier than iron. Is that origin theory still possible, or is it a mix of both?
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TheAnt
post Oct 19 2017, 05:27 PM
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QUOTE (Explorer1 @ Oct 19 2017, 02:43 AM) *
Incredible find!
I was under the impression that supernovas also create the elements heavier than iron. Is that origin theory still possible, or is it a mix of both?


A supernova should indeed produce some heavy elements if the theory is correct for them.

If I have understood this right, and I'm no physicist, the amounts of elements heavier than iron don't quite add up if only supernova explosions were the source.
For example the amount of the most heavy elements would be very small. Lets say the mass of Luna, our moon from one supernova.
When two neutron stars collide, they spew out 100 if not 1000's of times more material.
The part from the surface of the neutron star would be iron and elements from that medium heavy part of the periodic table, the other material will be neutronium.
Soon ˝ of the neutrons decay to protons capture electrons and create gold, uranium and the very heavy, and briefly existing, elements on row 7 of the periodic table.
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nogal
post Oct 19 2017, 10:00 PM
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QUOTE (moustifouette @ Oct 17 2017, 08:19 AM) *
First merger of neutron stars detected and observed both with gravity waves and electromagnetical ones.

ligo press release


See also INTEGRAL sees blast traveling with gravitational waves
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fredk
post Oct 21 2017, 03:10 PM
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QUOTE (JRehling @ Oct 18 2017, 11:25 PM) *
The neutron star merger is actually bigger news than the black hole mergers

A bit of an apples and oranges thing, perhaps. The BH mergers were extremely cool since we had direct observations of the "strong-field" regime of gravity, where the spacetime undergoes order-unity convolutions. That's many many many orders of magnitude stronger than anything we'd seen before, and Einstein's general relativity (GR) passed with flying colours.

The equality of electromagnetic and gravitational wave speeds is extremely cool, too. It's meant that many large classes of models for dark energy or modified gravity (extensions of GR) have been ruled out overnight.
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Floyd
post Oct 22 2017, 02:24 PM
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It is amazing that a lid was successfully placed on the news and the findings were successfully announcement at one time. An article in Science stated that the huge teams of physicists were unprepared for the chaos of astronomers in small competing groups---but they came together on one giant paper submitted to The Astrophysical Letters with 4600 authors--one third of the astronomy community. Wow, talk of big science.


--------------------
Floyd
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TheAnt
post Oct 27 2017, 11:42 AM
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QUOTE (Floyd @ Oct 22 2017, 04:24 PM) *
.....one third of the astronomy community. Wow, talk of big science.


They needed time to write, and embargoed each other (the cloak and dagger threat works fine in my field - and it's nothing regarding space at all) but it worked fine for them also.

Big science indeed, on the bottom of this page, and unusual for Universe today - a bibliographical list with 96 papers on arXiv.

@fredk: Yes you're right there that most MOND ideas have been thrown out the window, and also several models for Dark energy. I think the more outlandish idea of branes made it trough this unscathed.
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