Observation of Gravitational Waves from a Binary Black Hole Merger

[Atmos (Colin)]

Originally Posted by Eratosthenes

Q.3 What is "happening" at the point of contact and subsequent merging of the event horizons in the case of two black holes colliding and forming a single black hole? How do we geometrically and mathematically describe the event horizons of the two black holes as they touch and combine? Do special contact and intersection points form? If so, what happens at these points

[25 marks]

For the answer to that I deserve a Nobel Prize

[Eratosthenes (Peter)]

Originally Posted by Atmos

For the answer to that I deserve a Nobel Prize

I cant alter the [25 marks] for this particular question. It wouldnt be fair on all the other students who are sitting the exam.

Its interesting to note that the September 2015 measurement at the LIGO facility, occurred a few days prior to the official opening and whilst it was undergoing some tests before the ceremonial opening.

The LIGO researchers were working hard to meet the deadline and when they left the facility at 2:00AM in the morning, they decided to leave the detector on. The GW blimp decided to hit the earth a few hours later at about 4:50AM. I cant recall a measurement of this importance being taken under such circumstances. Incredible.

The researchers at LIGO used to secretly and deliberately disturb the mirrors to test the detector. They would write down when they did it and sealed it in an envelope. When a detection was made, word would go around to see if anybody tampered with the mirrors or detector. At 4:50AM that day, nobody produced an envelope. The signal was real.

Took a while to validate the signal (and rightly so)

[sjastro]

Originally Posted by Atmos

For the answer to that I deserve a Nobel Prize

Colin,

I suspect our resident troll got the answer he was looking for.

As a two body problem the interactions between Black Holes or objects of similar mass is an extremely difficult exercise in GR given it is a non linear theory.
GR "works" as a two body problem if there is sizeable difference in mass, such as Mercury's orbit.
In this case Mercury is treated as a point mass, and space time curvature is contributed from solar gravity.

GWs are split into two problems, one is how GWs are created, the other is how they propagate through space time. The propagation is the "relatively" easy part that can be handled by GR.

The creation of GWs by merging BHs is an entirely different matter and requires Numerical Relativity and tons of supercomputer time processing to come up with an answer.
In essence how BHs interact with each other is answered by mathematical modelling, computer algorithms as well as advances in computer hardware.

There is no simple answer to the question.

Regards

Steven

[Eratosthenes (Peter)]

Originally Posted by sjastro

The creation of GWs by merging BHs is an entirely different matter and requires Numerical Relativity and tons of supercomputer time processing to come up with an answer.
In essence how BHs interact with each other is answered by mathematical modelling, computer algorithms as well as advances in computer hardware.

I will check with xelas, but I think you will find that the modelling of the collision and merging of two black holes has nothing to do with access to supercomputers or the limitation of Numerical methodologies. Any scientist or mathematician worth their salt understands that the accuracy and applicability of Numerical simulations are grounded in the extent to which the mechanisms of the system/process are understood as well as the assumptions made.

In any case Black Hole collisions have already been simulated and these simulations require a lot less computer time and grunt than Climate and weather modelling simulations. The problem with singularity simulations and their theoretical descriptions is obtaining data and observations from nature in order to validate the models - after all the coupling and inter-validation of observation and theory is the most important pillar of the scientific method.

Its a little bit like String Theory which is more of a mathematical philosophy rather than a scientific idea due to its inherent lack of observational data to support it (so far). ST is closer to Catholicism than it is to Thermodymanics.

It's becoming more and more common for scientists to drift into the realm of religious fundamentalism as they pray in their temples everyday and chant the verses from their Scriptures like subserviant corproatised state puppets.

I hope xelas is able to forgive your little error

[Shiraz (Ray)]

Originally Posted by Eratosthenes

It's becoming more and more common for scientists to drift into the realm of religious fundamentalism as they pray in their temples everyday and chant the verses from their Scriptures like subserviant corproatised state puppets.

I hope xelas is able to forgive your little error

Oh for heavens sake - this cracked record is getting distinctly boring

[xelasnave]

So tell me Peter how do we fix the problem

[xelasnave]

and Peter it seems that you do have a problem.
This constant ranting has become as Ray says somewhat like a broken record.
Your rants worry me. I worry you are not well.
Can I help if you need a friend I am here for you.

[sjastro]

Originally Posted by xelasnave

and Peter it seems that you do have a problem.
This constant ranting has become as Ray says somewhat like a broken record.
Your rants worry me. I worry you are not well.
Can I help if you need a friend I am here for you.

That is a very admirable attitude Alex.
As a result I won't respond to his latest post.

[Eratosthenes (Peter)]

Originally Posted by Shiraz

Oh for heavens sake - this cracked record is getting distinctly boring

I think you will find that most exams are boring, but the candidates must still try to maximise the marks they receive for each question. Bruce didnt do well with Q3 unfortunately. Although I must say that I was refreshingly surprised with the candor and honesty displayed by Colin. Bonus marks there for sure.Well done Colin!

[Eratosthenes (Peter)]

Originally Posted by xelasnave

So tell me Peter how do we fix the problem

which problem are you referring to xelas?

Well done by the way xelas, well done on your tireless efforts in this particular forum.

[xelasnave]

Well its this way Peter your attacks rants and insults are disruptive. You seem like a nice enough bloke and quiet intelligent but you persist in behaviour that is upsetting to members.
So I wonder why you lash out the way you do.
I could speculate upon your reasons and when I do I think you are suffering some hurt that causes you to act in an anti social manner.
You could think about that and ask yourself if your personal image of yourself is well served given you choose to alienate folk with specific insults and generalizations as to the science and its short falls.
You may feel inadequate or superior I don't know.
But I ask you please be decent.
If you want insult me I will be a non moving target..and if that helps you recover your self esteem I will be happy for you.
But I ask again please don't insult people and rant about scienc.

[Eratosthenes (Peter)]

Originally Posted by xelasnave

Well its this way Peter your attacks rants and insults are disruptive. You seem like a nice enough bloke and quiet intelligent but you persist in behaviour that is upsetting to members.
So I wonder why you lash out the way you do.
I could speculate upon your reasons and when I do I think you are suffering some hurt that causes you to act in an anti social manner.
You could think about that and ask yourself if your personal image of yourself is well served given you choose to alienate folk with specific insults and generalizations as to the science and its short falls.
You may feel inadequate or superior I don't know.
But I ask you please be decent.
If you want insult me I will be a non moving target..and if that helps you recover your self esteem I will be happy for you.
But I ask again please don't insult people and rant about scienc.

I see xelas.

I will need to review your comments in more detail.

This review shouldnt take more than 9 or 10 months, so I will see you all back here, same time, same channel in early 2017.

[Shiraz (Ray)]

Some more details on the second candidate event (a binary BH 23 +13 merger) are at https://dcc.ligo.org/public/0123/P15...CBC_Search.pdf
This paper gives a comprehensive summary of the signal processing - very interesting methodolgy. Also interesting that signal strength is now being discussed in audio terms - loudnenss. The paper points out the fundamental problem in determining noise statistics in this task - there is no way to isolate the system from GW signals and just look at noise (nothing can shield against GWs).

"Both analyses reported a candidate event on October 12, 2015 at 09:54:43 UTC as the second-loudest event in the observation period,
which we refer to as LVT151012. This candidate event has
a combined matched-filter SNR of 9.6. The PyCBC analysis
reported a false alarm rate of 1 per 2.3 years and a corresponding
false alarm probability of 0.02 for this event. The
GstLAL analysis reported a false alarm rate of 1 per 1.1 years
and a false alarm probability of 0.05. These results are consistent
with expectations for candidate events with low matched-
filter SNR, since PyCBC and GstLAL use different ranking
statistics and background estimation methods. Detector characterization
studies have not identified an instrumental or environmental
artifact as causing this candidate event [14], however
its false alarm probability is not sufficiently low to con-
fidently claim the event as a signal. It is significant enough
to warrant follow-up, however. The results of signal parameter
estimation, shown in Table I, indicate that if LVT151012
is of astrophysical origin, then the source would be a stellarmass
binary black hole system with source-frame component
masses 23+18
−5 M and 13+4
−5 M. The effective spin would be
χeff = 0.0
+0.3
−0.2
and the distance 1100+500
−500 Mpc.

[silv (Annette)]

I LOVE how the first two pages list the co-authors
How wonderful that in our age of the internet, those names won't be falling off the table like in the olden days, when the fourth author already got no reference anymore, library-wise, and was forgotten, forever.

Interesting and again exciting that the coinciding gamma ray blast was found when crawling back through the data.
and then again, was not found by the other data set. intriguing. yay.

Maybe Fermi detected the influx from our own sun?
It sure is close to the event time of 9.50 UTC:

Space Weather Message Code: ALTEF3
Serial Number: 2248
Issue Time: 2015 Sep 14 1011 UTC
CONTINUED ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
Continuation of Serial Number: 2247
Begin Time: 2015 Sep 10 1020 UTC
Yesterday Maximum 2MeV Flux: 11910 pfu
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Satellite systems may experience significant charging resulting in increased risk to satellite systems.

quoted from ftp://ftp.swpc.noaa.gov/pub/alerts/ , specifically alerts_201509.html - a rather active period as the attached graph from the same archive shows.

I can only assume that a "Continued Alert" is actually triggered by a new overstepping of certain thresholds. I assume that based on the fact that the continuation alerts come with different time stamps as can also be seen in the graph.
In which case, in the morning, just before 10.11UTC, incoming "stuff" from our sun has triggered this NOAA alarm. and it might be what the Fermi data back crawl team has found in their data, too.
If the Fermi-measurement was anything above normal background noise, of course.

[silv (Annette)]

unrelated:
From the Max Planck response to the find:
"While supermassive black holes are often accompanied by substantial disks, black holes of stellar mass lose the disk created during the progenitor star collapse on a time scale of the order of τdisk ∼ 100 s."
In my association this connects to the dumbell-explanation of a single star source for the 2 BH and how quickly this dumbell-forming and colliding would happen.

Here, the two very short-lived accretion disks might have very quickly amassed enough to stream the stuff off into the void...just before they die in each other's arms,
to form a new BH.
There's a bit of tragic cosmical romance or a little soft-porn in it, don't you think?