Are pulsars gravity-wave generators?

Nuadormrac
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According to the article,

According to the article, there is a slightly faster pulsar (about 640 rps) but that emits radio waves, not x-rays, which makes this one somewhat unique in terms of the one's we've detected so far.

It is possible that they formerly thought the rate at which it could spin and still be stable wass lower then what they're thinking now...though the article does say 3k rps...

And yes, this very much touches upon what we're looking at with this project; but I suppose the reason we haven't all said much, is we're waiting to see what comment the project heads/scientists have to say on this very discovery/should they want to say something...

As to questions such as

> I am not sure but I think that most of these Ligo and Geo600 things have most
> of their sensitivities at the low end things ( a few orders of magnitude from
> 10's to 1000's Hz). I sure hope that this project tells us more about the
> science here and less about the computer games.

> If anyone knows the frequency sensitivites of our searches, please post them.
> There has to be someone out there that knows the astronomy, what is really
> going on in these programs.

they would be the best qualified to inform us, as it's their project. I'd be curious as to the answer myself...

Stevious
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I would also like to learn

Message 4114 in response to message 4113

I would also like to learn more about the specifics of the project and what exactly we're crunching for. There is a broad statement on the homepage saying that "This first production run of Einstein@home carries out a search for pulsars over the entire sky".

I followed the Einstein@Home in the news hyperlinks, but that's just second-hand information being filtered through the news media. What I would like to see is in-depth/technical information on http://einstein.phys.uwm.edu/

Afterall, if we are to donate our spare cycles to the project, we're owed at least that much. Many of us studied Math and Physics in college. Inquiring minds want to know! More info, please. :)

Edit: I did search the messageboard for information, but that's not always the easiest method.

Ben Owen
Ben Owen
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Hi folks, I can answer a

Hi folks,

I can answer a couple of these questions. I'm one of the designated Science Answer Guys and I have a spare moment. We do appreciate your desire to know something about the science (and pick it out of the board traffic). Bruce has plans to spiff up the boards and Q&A a bit; it's just that he (and the other coders) have their hands more than full right now making sure the guts of the project are working.

The answer to the thread title is "yes." All pulsars should generate some gravitational waves; it's just a question of how strong. That is very poorly constrained by theory, and the work units you are crunching are dedicated towards firming that up with observation.

Most pulsars should generate most of their gravitational wave signal at twice the spin frequency. So the 641 Hz pulsar, which is the fastest currently known, should emit gravitational waves at 1282 Hz. Broadly speaking, the detectors are sensitive from there down to a few tens of Hz, but the signals generally get fainter at lower frequencies and the noise starts getting stronger below about 150-200 Hz.

The maximum frequency a pulsar could spin at is also poorly constrained by theory. It's proportional to the square root of the density of the neutron star, but that density isn't known to any better precision than a factor of 3-4. So it could be 3000 Hz (or even higher in some really far-out theories), or it could be that the 641 Hz is the fastest possible. The maximum frequency isn't the same for all stars, either. It depends on the mass, and the masses are known from radio observations to vary somewhat. So the 641 Hz pulsar might be a heavy one spinning at half its breakup frequency, and at the same time the 619 Hz one might be a lightweight on the verge of flying apart.

I should say that if you do know the density, the maximum spin frequency is pretty easy to work out if you've had freshman physics. By definition it's when the star is on the edge of flying apart due to the centrifugal force, so you can consider the stuff on the equator to be in orbit. Work out the orbital velocity of a particle around an object of radius R and mass M and there you are. (That's the Newtonian gravity answer, but surprisingly relativity doesn't change the answer more than a few percent for any given M and R. It does change what M and R really mean, though....)

There are answers to a few more questions in my previous posts, which you can look up in my profile.

Hope this helps,
Ben

Dennis
Dennis
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> Hi folks, > > I can answer

Message 4116 in response to message 4115

> Hi folks,
>
> I can answer a couple of these questions. I'm one of the designated Science
> Answer Guys and I have a spare moment. We do appreciate your desire to know
> something about the science (and pick it out of the board traffic). Bruce has
> plans to spiff up the boards and Q&A a bit; it's just that he (and the
> other coders) have their hands more than full right now making sure the guts
> of the project are working.
> .......................> There are answers to a few more questions in my previous posts, which you can
> look up in my profile.
>
> Hope this helps,
> Ben
>
Thanks,
so basically are our little WU just searching through the sky to find periods of 100 to 1000 or so signals. Are different WU just data taken at different times or something like that? And the results that are compared to be verified check to see if we come up with the same period signals at the same locations in the sky?

Please forgive me, I am the kind that is more interested in the science behind all this crunching than what computer does what how fast. I guess I may need to wait a while - that is OK, I imagine you "wizards" are busy right now. But later please let us know what we are really doing with all this computer time. I can look up the physics but I have no idea what these WU are really working on.

Thanks again,

Dennis

BillyG
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> Hope this helps, >

Message 4117 in response to message 4115

> Hope this helps,
> Ben

Thanks Ben. That's 100% more info on this project than what I had before, us lowly "users" appreciate your input!

.
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Bernd Machenschalk
Bernd Machenschalk
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> so basically are our little

Message 4118 in response to message 4116

> so basically are our little WU just searching through the sky to find periods
> of 100 to 1000 or so signals. Are different WU just data taken at different
> times or something like that?

The Wurkunits differ mainly in the frequency band they are searching. And yes, also a bit in the time when the samples are taken. The frequency you are looking for is currently coded in the name of the Results - not hard to see.

BM

BM

cIclops
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> Most pulsars should

Message 4119 in response to message 4115

> Most pulsars should generate most of their gravitational wave signal at twice
> the spin frequency.

Hopefully you can enlighten me regarding the physics of extreme objects such as these spinning neutron stars. Given that we (hopefully) observe gravitational waves as observers high up in the deep gravitational well of a neutron star (10^11 G) won't the time dilation effect significantly change the frequency that we observe?

--
searching for gravitational waves since 2005

Dennis
Dennis
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> > so basically are our

Message 4120 in response to message 4118

> > so basically are our little WU just searching through the sky to find
> periods
> > of 100 to 1000 or so signals. Are different WU just data taken at
> different
> > times or something like that?
>
> The Wurkunits differ mainly in the frequency band they are searching. And yes,
> also a bit in the time when the samples are taken. The frequency you are
> looking for is currently coded in the name of the Results - not hard to see.
>
> BM
>
Thanks, that is exactly the kind of info I was hoping for.

I am not sure what I am seeing. For example one of my WU is named:
H1_0510.9__0511.4_0.1_T01_Test02_0

Does that mean that it is searching for periods of 510.9 to 511.4 Hz????

Thanks again,
Dennis

BillyG
BillyG
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> one of my WU is named: >

Message 4121 in response to message 4120

> one of my WU is named:
> H1_0510.9__0511.4_0.1_T01_Test02_0
>
> Does that mean that it is searching for periods of 510.9 to 511.4 Hz????

sounds right but that's a good question Dennis

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I HAVE BEEN RUNNING 24/7 SINCE (not counting server WAIT times lol), CHECKOUT MY STATS!


Dennis
Dennis
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> > Most pulsars should

Message 4122 in response to message 4119

> > Most pulsars should generate most of their gravitational wave signal at
> twice
> > the spin frequency.
>
> Hopefully you can enlighten me regarding the physics of extreme objects such
> as these spinning neutron stars. Given that we (hopefully) observe
> gravitational waves as observers high up in the deep gravitational well of a
> neutron star (10^11 G) won't the time dilation effect significantly change the
> frequency that we observe?
>

As I understand it, the frequency of the emission is shifted but what we are looking at is the period of the rotation of the pulsar. It is like a little lighthouse. It is not about the "color" (or colour for you brits) of the light beam but about how fast the beam is rotated (time between flashes). These things have had their radius decreased and like an ice skater, their rotational speed increases as the mass goes from the size of the sun (+) down to a few tens of miles.
See:
http://www.ucolick.org/~bolte/AY4/notes13/node2.html

These things have a big magnetic field due to rotation and their light/radio waves come out in a beam.
We (E@H crunchers) are looking at certain frequencies across the sky to see if we see any pulsars with that "flash rate". As time goes on the "flash rate" (=period) should increase and give an idea at how fast they are loosing energy.
If we are lucky enough to find two pulsars close together, the rate at which they slow down their orbits around each other should indicate that they are loosing energy (=mass) in the form of gravity waves.
see:
http://www.ucolick.org/~bolte/AY4/notes13/node2.html

Take what I say as coming from just an amateur.......it is my best guess as to what we are doing. I assume they will tell us more as the wizards get more time after the program bugs are fixed.

Dennis

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