"O1Spot1" Continuous Gravitational Wave Galactic Center search started

hoarfrost
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solling2 wrote:hoarfrost

solling2 wrote:
hoarfrost wrote:

Hello!

The signal from which sources we are currently looking for? From pair of central Huge Black Hole (n*10^6 Msun) with other presumable black hole (m*10^5 Msun)?

Thank you!

This search is primarily going for CONTINUOUS waves. These are expected from asymmetric pulsars. However, this question is more related to the science section than to this thread which primarily refers to the app. Anyway, just keep on crunching!

If sources of gravitation waves now is only converge, can emitted waves be continuous in therms of this search?

Or period of this waves would be too large?

solling2
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hoarfrost schrieb: If

hoarfrost wrote:

If sources of gravitation waves now is only converge, can emitted waves be continuous in therms of this search?

Or period of this waves would be too large?

Two objects, like two black holes or two neutron stars approaching and finally colliding, emit a different type or a different pattern of gravitational waves from what an asymmetric neutron star emits. Searching for that pattern of two objects is what the LIGO team is doing, whereas searching for a continuous pattern is what you are doing in this project. So again, we'll just have to keep on crunching. :-)

More to the technical aspects of this thread, I'd be curious to know whether the O1... app might benefit from a wisdom file given the success we've seen with the FGRP...1.08 app recently.

Bernd Machenschalk
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solling2 wrote:More to the

solling2 wrote:

More to the technical aspects of this thread, I'd be curious to know whether the O1... app might benefit from a wisdom file given the success we've seen with the FGRP...1.08 app recently.

Yes it will. I recently filed an internal pull request to make the current GW app read wisdom from a file. Once this has been merged, we'll build new app versions and publish these.

BM

hoarfrost
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solling2 написал:hoarfrost

solling2 wrote:
hoarfrost wrote:

If sources of gravitation waves now is only converge, can emitted waves be continuous in therms of this search?

Or period of this waves would be too large?

Two objects, like two black holes or two neutron stars approaching and finally colliding, emit a different type or a different pattern of gravitational waves from what an asymmetric neutron star emits.

Yes, of course. I'm understand this. :)

But what is "continuous" in therms of this search? "Shape" of desired signal or time during which its shape looks constant? (For example - pair of black holes for 1 million years before merge).

In this search we try to detect waves from neutron stars, located near Galactic Centre?

Thank you!

Bernd Machenschalk
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The (detectable)

The (detectable) gravitational wave emitted from a "collision" (actually more a "merge") of two massive objects is pretty strong, but only lasts for fractions of a second. Gravitational waves emitted from spinning neutron stars are much, much weaker, but should last for years with only little, predictable change in frequency (or so we hope), so they are called "continuous" gravitational waves. The good thing is that you can somewhat accumulate the power of the signal over time, as long as you can record it. Thus in theory your sensitivity for those signals is limited only by the amount of data that you can collect and process computationally. This is why we look for this specific type of signals with a machinery like Einstein@Home.

Indeed the current search focuses ("spotlights") on sources from the galactic center.

BM

hoarfrost
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Bernd, thank you for

Bernd, thank you for explanation!

Mad_Max
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Bernd Machenschalk

Bernd Machenschalk wrote:

The (detectable) gravitational wave emitted from a "collision" (actually more a "merge") of two massive objects is pretty strong, but only lasts for fractions of a second. Gravitational waves emitted from spinning neutron stars are much, much weaker, but should last for years with only little, predictable change in frequency (or so we hope), so they are called "continuous" gravitational waves. The good thing is that you can somewhat accumulate the power of the signal over time, as long as you can record it. Thus in theory your sensitivity for those signals is limited only by the amount of data that you can collect and process computationally. This is why we look for this specific type of signals with a machinery like Einstein@Home.

Indeed the current search focuses ("spotlights") on sources from the galactic center.

 

But if we looking for tight binary system of 2 black holes (or pair of neutron stars, or BH+NS) long before actual merger happens (e.g. from few dozen of years to thousands years before merger event) these systems will also generate weak but continuous GW with very stable parameters.

I thought we are looking for such sources in "continuous" searches...

If i understand correctly - single spinning neutron star produces any significant continuous GW only if it asymmetrical in shape? And AFAIK there are no any poofs that such NS exist at all, yet. They all could be very close to ideal sphere.

But we already KNOW that tight binary systems of extreme  dense objects (BH+BH, NS+NS, NS+BS) exist. Thus sources of continuous GW also exist.

Is there any plans for search of continuous GW signals from these sources?

Bernd Machenschalk
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The frequency of these

The frequency of these gravitational waves is below the range of what our ground-based observatories can detect. These waves only come into the detectable frequency range when the Black Holes or Neutron Stars are pretty close, orbiting each other very fast, only seconds before the actual merge.

These waves will only be detectable by LISA, the planned space-based GW detector.

BM

Mad_Max
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Hmm. But such binary systems

Hmm. But such binary systems have full continuous spectra from very low for binary systems millions or thousands years before merger (like PSR J0737−3039:  ~2.5 hr orbital period but it at least millions years before those NS will merge) to very high at very end (like hundreds HZ / few ms orbital period at recent BH merger detections).
And I thought that there are must be some objects in between with  frequencies in range about 0.1 - 10 Hz and relative long life time span (time remaining before merger event). Which should be reachable by ground detector with lower sensitivity of course, but this sensitivity loss compensated by long observation times and intense calculation.

But now i am trying to do some calculation. And if i did not do mistake and too much assumptions it looks like best objects we can try to catch is something like:

2 NS (~1.5 solar mass each) at 1000 km distance ==> ~ 4 Hz starting frequency of GW but only ~1 hour life time before merger

same at 10 000 km ==> ~1 year LF but only ~0.1 Hz GW

2 BH (~5 SM) @ 10 000 km ==> 0.3 Hz and few days before merger.

Is this numbers near correct (e.g. in same order of magnitude - it just rough estimates) ?

If soo it looks like we have too low frequency (if think LIGO record almost only a seismic noise < 1 Hz ?) or too short life time and event will be detected by online LIGO monitoring fist before full data set collected and can be analyzed.

Last question. What is order of magnitude for sensitivity gain if we compare short events like merger where only a few dozen orbital periods are analyzed with the power of relatively simple computations and patterns in online ongoing searches versus analyze of records of very large lengths of nearly constant waves using a tool such as E@H for intensive computation?

Mike Hewson
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Mad_Max wrote:Hmm. But such

Mad_Max wrote:

Hmm. But such binary systems have full continuous spectra from very low for binary systems millions or thousands years before merger (like PSR J0737−3039:  ~2.5 hr orbital period but it at least millions years before those NS will merge) to very high at very end (like hundreds HZ / few ms orbital period at recent BH merger detections).
And I thought that there are must be some objects in between with  frequencies in range about 0.1 - 10 Hz and relative long life time span (time remaining before merger event). Which should be reachable by ground detector with lower sensitivity of course, but this sensitivity loss compensated by long observation times and intense calculation.

But now i am trying to do some calculation. And if i did not do mistake and too much assumptions it looks like best objects we can try to catch is something like:

2 NS (~1.5 solar mass each) at 1000 km distance ==> ~ 4 Hz starting frequency of GW but only ~1 hour life time before merger

same at 10 000 km ==> ~1 year LF but only ~0.1 Hz GW

2 BH (~5 SM) @ 10 000 km ==> 0.3 Hz and few days before merger.

Is this numbers near correct (e.g. in same order of magnitude - it just rough estimates) ?

If soo it looks like we have too low frequency (if think LIGO record almost only a seismic noise < 1 Hz ?) or too short life time and event will be detected by online LIGO monitoring fist before full data set collected and can be analyzed.

For the LIGO detectors about 10 Hz to a few thousand Hz is the quoted dynamic range. Reception lower than that is dominated by effects related to being on a planet, higher than that is largely a matter of optics. However the 'sweet spot' with maximal sensitivity is about 200 hz. As demonstrated inspiralling binary systems don't last very long in that band ! 'Continuous' for E@H purposes may be defined as having a low rate of change of frequency and thus remaining sufficiently coherent over long integration times when we 'fold' a recorded signal to catch a candidate waveform. If the frequency changes too much the ( Fourier ) transform will have a lower peak and won't reach sufficient signal-to-noise to trigger the detection statistic threshold. In general LIGO likes a five sigma result or better to claim a discovery.

Quote:
Last question. What is order of magnitude for sensitivity gain if we compare short events like merger where only a few dozen orbital periods are analyzed with the power of relatively simple computations and patterns in online ongoing searches versus analyze of records of very large lengths of nearly constant waves using a tool such as E@H for intensive computation?

Don't know. But I reckon the short answer is that it's our job to do continuous waves. Someone has to I suppose. :-)

The multi-petaflop capability of E@H makes us highly suited for this ( dare I say quite tedious ? ) work. The scientific payoff, like the rest of this new GW venture, is quite high if we score though ! :-))

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter ...

... and my other CPU is a Ryzen 5950X :-) Blaise Pascal

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