Author Topic: Gravitational Waves Have Been Detected At LIGO  (Read 58982 times)

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #260 on: 10/17/2017 06:56 AM »
A bunch of papers are now all on arxiv.org:

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817:
* https://arxiv.org/abs/1710.05459 I. Dark Energy Camera Discovery of the Optical Counterpart
* https://arxiv.org/abs/1710.05440 II. UV, Optical, and Near-IR Light Curves and Comparison to Kilonova Models
* https://arxiv.org/abs/1710.05456 III. Optical and UV Spectra of a Blue Kilonova From Fast Polar Ejecta
* https://arxiv.org/abs/1710.05454 IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South
* https://arxiv.org/abs/1710.05431 V. Rising X-ray Emission from an Off-Axis Jet
* https://arxiv.org/abs/1710.05457 VI. Radio Constraints on a Relativistic Jet and Predictions for Late-Time Emission from the Kilonova Ejecta
* https://arxiv.org/abs/1710.05458 VII. Properties of the Host Galaxy and Constraints on the Merger Timescale
* https://arxiv.org/abs/1710.05438 VIII. A Comparison to Cosmological Short-duration Gamma-ray Bursts

I've only included the 8 summary papers on the electromagnetic counterpart.  There are *load* of papers from individual observatories and exploring various topics (a total of 64!) ... but there's a lot of reading there :-)

--- Tony

« Last Edit: 10/17/2017 06:57 AM by jebbo »

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #261 on: 10/17/2017 07:02 AM »
I remember from The Atlantic article that this event is also helping with the cosmic scale distance. Apparently gravitational waves also measure distance (or is it some other observation?) and this gives an independent measure of the distance of that galaxy, helping constrain the cosmic ladder. More information would be welcome

Yes indeed.  The paper you are looking for is here: https://arxiv.org/abs/1710.05835

--- Tony

Offline bolun

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #262 on: 10/17/2017 10:14 AM »
INTEGRAL SEES BLAST TRAVELLING WITH GRAVITATIONAL WAVES

16 October 2017

ESA's INTEGRAL satellite recently played a crucial role in discovering the flash of gamma rays linked to the gravitational waves released by the collision of two neutron stars.

On 17 August, a burst of gamma rays lit up in space for almost two seconds. It was promptly recorded by INTEGRAL and NASA's Fermi satellite.

Such short gamma-ray bursts are not uncommon: INTEGRAL catches about 20 every year. But this one was special: just seconds before the two satellites saw the blast, an entirely different instrument was triggered on Earth.

One of the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) experiment, in the USA, recorded the passage of gravitational waves fluctuations in the fabric of spacetime caused by powerful cosmic events.

http://sci.esa.int/integral/59664-integral-sees-blast-travelling-with-gravitational-waves/

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #263 on: 10/17/2017 02:52 PM »
The LIGO folks are doing a Reddit Ask Me Anything at 15:00 GMT.

Here: https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/

--- Tony

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #264 on: 10/17/2017 04:18 PM »
The LIGO folks are doing a Reddit Ask Me Anything at 15:00 GMT.

Here: https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/

--- Tony

I noticed on there someone asked what secondary applications LIGO has. I am sure I read in the New Scientist its considered a highly sensitive seismic detector, that actual scientific research is done from this side as well?

Offline Hungry4info3

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #265 on: 10/17/2017 10:51 PM »
So this is going to be a question straight out of the depths of my uninformed, nave mind, and I apologise in advance for that. One of the take-aways I get from this discovery is that g-waves are confirmed to move at the speed of light. My understanding is that g-waves are distortions in space-time. If changes in space-time can move only at velocities limited to the speed of light, does this automatically rule out Alcubierre-type "warp drive" systems? (aside from all the obvious stuff about a lack of plausible mechanism to generate negative energy density, etc).

Online meberbs

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #266 on: 10/17/2017 11:13 PM »
So this is going to be a question straight out of the depths of my uninformed, nave mind, and I apologise in advance for that. One of the take-aways I get from this discovery is that g-waves are confirmed to move at the speed of light. My understanding is that g-waves are distortions in space-time. If changes in space-time can move only at velocities limited to the speed of light, does this automatically rule out Alcubierre-type "warp drive" systems? (aside from all the obvious stuff about a lack of plausible mechanism to generate negative energy density, etc).
Alcubierre warp drive (with caveats you mentioned) is predicted by the same theory of GR that predicts that gravitational waves travel at the speed of light, so this should be support not contradiction. Now that you point it out it does seem strange, but there are many stranger things in physics, especially some of the other things you could do with negative energy density.

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #267 on: 10/18/2017 05:54 AM »
So this is going to be a question straight out of the depths of my uninformed, nave mind, and I apologise in advance for that. One of the take-aways I get from this discovery is that g-waves are confirmed to move at the speed of light. My understanding is that g-waves are distortions in space-time. If changes in space-time can move only at velocities limited to the speed of light, does this automatically rule out Alcubierre-type "warp drive" systems? (aside from all the obvious stuff about a lack of plausible mechanism to generate negative energy density, etc).
Alcubierre warp drive (with caveats you mentioned) is predicted by the same theory of GR that predicts that gravitational waves travel at the speed of light, so this should be support not contradiction. Now that you point it out it does seem strange, but there are many stranger things in physics, especially some of the other things you could do with negative energy density.

I am surprised to hear that people thought that gravity might move at anything other than the speed of light.

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #268 on: 10/18/2017 06:35 AM »
I am surprised to hear that people thought that gravity might move at anything other than the speed of light.

This gets a lengthy treatment in section 4 here: http://iopscience.iop.org/article/10.3847/2041-8213/aa920c/meta.

tl;dr the expectation is they propagate at identical speeds, and this event puts stringent constraints on any deviation from that  :)

--- Tony

Offline CuddlyRocket

Re: Gravitational Waves Have Been Detected At LIGO
« Reply #269 on: 10/18/2017 06:17 PM »
Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?

A white dwarf merger would result in a supernova that would completely disrupt both stars.

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #270 on: 10/18/2017 06:33 PM »
Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?

A white dwarf merger would result in a supernova that would completely disrupt both stars.

But wouldnt some kind of body still be left behind?

Online jgoldader

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #271 on: 10/18/2017 08:01 PM »
I wondered too, and a quick look turned up this paper
http://iopscience.iop.org/article/10.1088/0004-637X/746/1/62/meta

which suggests a remnant is usually left behind after white dwarf mergers.  IANA stellar evolution expert, but what the remnant is, depends on the total mass left over after the explosion.  For low enough remnant masses, it would be another carbon-oxygen degenerate star, like a white dwarf; but you'd get a neutron star if the remnant mass exceeds the Chandrasekhar limit of about 1.4 M_sun, the most massive an object held up by electron degeneracy can be.  I don't think two WDs colliding could make a black hole; those typically shouldn't show up below 3 M_sun, which is greater than twice the Chandrasekhar limit.

Reminds me of the Calvin & Hobbes cartoon where Calvin's playing with his toys, and he's got several things crashing together at the same time, and he says something like, "This is gonna be good!"
« Last Edit: 10/18/2017 08:02 PM by jgoldader »
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Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #272 on: 10/18/2017 08:16 PM »
There's also this https://arxiv.org/abs/1505.01646

--- Tony

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #273 on: 11/09/2017 09:33 PM »
Giant star smash-up may have made the biggest neutron star ever

Quote
When we watched two neutron stars smash into each other in August, producing gravitational waves and a huge explosion, we werent quite sure what was left over afterward: a single colossal neutron star or a black hole.

Now, Yun-Wei Yu at Central China Normal University and Zi-Gao Dai at Nanjing University in China have modelled that explosion, a so-called kilonova that could last weeks to months, and they say there is a neutron star left over at the spot where the smash-up occurred.

https://www.newscientist.com/article/2152822-giant-star-smash-up-may-have-made-the-biggest-neutron-star-ever/

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #274 on: 11/13/2017 07:41 PM »
Listening for Gravitational Waves Using Pulsars

https://www.jpl.nasa.gov/news/news.php?feature=6998

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #275 on: 11/16/2017 08:07 AM »
Another detection

GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence

Quote
On June 8, 2017 at 02:01:16.49 UTC, a gravitational-wave signal from the merger of two stellar-mass black holes was observed by the two Advanced LIGO detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses 12+7−2M⊙ and 7+2−2M⊙ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through gravitational waves with electromagnetic observations. The source's luminosity distance is 340+140−140 Mpc, corresponding to redshift 0.07+0.03−0.03. We verify that the signal waveform is consistent with the predictions of general relativity.

https://arxiv.org/abs/1711.05578

--- Tony

Offline Star One

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Gravitational Waves Have Been Detected At LIGO
« Reply #276 on: 11/16/2017 09:33 AM »
Heres the press release for the detection.

LIGO and Virgo announce the detection of a black hole binary merger from June 8, 2017

Quote
News Release November 15, 2017

Scientists searching for gravitational waves have confirmed yet another detection from their fruitful observing run earlier this year. Dubbed GW170608, the latest discovery was produced by the merger of two relatively light black holes, 7 and 12 times the mass of the sun, at a distance of about a billion light-years from Earth. The merger left behind a final black hole 18 times the mass of the sun, meaning that energy equivalent to about 1 solar mass was emitted as gravitational waves during the collision.

This event, detected by the two NSF-supported LIGO detectors at 02:01:16 UTC on June 8, 2017 (or 10:01:16 pm on June 7 in US Eastern Daylight time), was actually the second binary black hole merger observed during LIGOs second observation run since being upgraded in a program called Advanced LIGO.  But its announcement was delayed due to the time required to understand two other discoveries: a LIGO-Virgo three-detector observation of gravitational waves from another binary black hole merger (GW170814) on August 14, and the first-ever detection of a binary neutron star merger (GW170817) in light and gravitational waves on August 17.

A paper describing the newly confirmed observation, GW170608: Observation of a 19-solar-mass binary black hole coalescence, authored by the LIGO Scientific Collaboration and the Virgo Collaboration has been submitted to The Astrophysical Journal Letters and is available to read on the arXiv. Additional information for the scientific and general public can be found at

https://www.ligo.caltech.edu/news/ligo20171115?source=techstories.org
« Last Edit: 11/16/2017 09:36 AM by Star One »

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