Searching for pulsars in PALFA data from Arecibo

Kotulic Bunta
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RE: ...due to ... smaller

Message 89015 in response to message 89012

Quote:
...due to ... smaller template bank it does this much faster...

Does it mean that the number of combinations of orbital radius+period+phase according to which the data are analysed in each WU has been decreased? If yes, isn't it "bluring" the possible signal and thus decreasing the probability of discovery?

Mike Hewson
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RE: RE: ...due to ...

Message 89016 in response to message 89015

Quote:
Quote:
...due to ... smaller template bank it does this much faster...

Does it mean that the number of combinations of orbital radius+period+phase according to which the data are analysed in each WU has been decreased? If yes, isn't it "bluring" the possible signal and thus decreasing the probability of discovery?


IIRC the template refers to the putative signal waveform shape - so my guess is the smaller template/precision is a 'blunter' approximation.

Cheers, Mike.

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

hoarfrost
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Hello! What is "Progress

Hello!

What is "Progress in C, N, S grid" that shown on Einstein@Home Arecibo Binary Radio Pulsar Search Progress Page?

Mad_Max
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I join the previous question.

I join the previous question. You can give a brief explanation of the meaning of these graphs? At the crunchers level?
For example why the latitude has range of only -3 ... 3 degrees, I can understand - because our galaxy is relatively "flat" (a "disc" rather than the ball)? But why longitude not 360 degrees? What does "C, N, S grid" means?
% of done corresponds to DM (distance) which were calculated or multiple observations of one and the same portion of the sky or anticipated frequency of rotation of pulsars? Or all simultaneously?

And why the graphs is made up of individual dots with wide intervals between them? Is search is not on a continuous parameter space?

Bernd Machenschalk
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Basically this is a detailed

Basically this is a detailed progress counter for three different data sets from Arecibo data. I pointed Benjamin to this thread, he should be able to give a more detailed explanation.

BM

BM

Bikeman (Heinz-Bernd Eggenstein)
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I'd guess that there are

I'd guess that there are certain constraints on the part of the galaxy that is surveyable by Arecibo, both by

a) the geographic location of Arecibo
b) the mechanics of the dish

The dish is fixed, but you can aim the telescope by moving secondary reflector dome a bit.

Right?

HB

Benjamin Knispel
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RE: I join the previous

Message 89021 in response to message 89018

Quote:
I join the previous question. You can give a brief explanation of the meaning of these graphs? At the crunchers level?
For example why the latitude has range of only -3 ... 3 degrees, I can understand - because our galaxy is relatively "flat" (a "disc" rather than the ball)?

Exactly. Pulsars are expected to be abundant near the Galactic disk where they are born. This is why the PALFA search is focusing on this narrow window in Galactic latitude.

Quote:

But why longitude not 360 degrees?

Arecibo can only see a limited part of the sky because it can basically look straight up and a bit (20°) away from the zenith (straight up). So, there's a 40° wide corridor of the sky that passes the viewfield of Arecibo being carried in and out by the rotation of the Earth. This corridor intersects with the plane of our Galaxy in two parts of the sky: one is closer to the Galactic center and this is the patch of sky you can see in the plots, the other one is a patch opposite in the sky. Data from the second patch have not been analysed by Einstein@Home but will be analysed in the near future.

Quote:

What does "C, N, S grid" means?

The receiver used at Arecibo for the survey has seven beams that observe seven adjacent tiny patches (diameter of each patch about a eighth of the diameter of the Full Moon) in the sky simultaneously. The seven beams are arranged in a hexagon with one beam in the center and the others at the corners. To cover the whole search space in sky efficiently there are three grids (called C, N, and S) of the hexagons interleaved with each other. Please look at Fig. 1 and Fig.3 in this paper to get a nice picture of it.

Quote:

% of done corresponds to DM (distance) which were calculated or multiple observations of one and the same portion of the sky or anticipated frequency of rotation of pulsars? Or all simultaneously?

Each dot in the plots stands for the central of the seven beams only. So the "% done" tells you how many of the 628 DM values of all of the seven beams have been done. The quantization here is 1 / (628 * 7).

Quote:

And why the graphs is made up of individual dots with wide intervals between them? Is search is not on a continuous parameter space?

The sky is a continuous parameter space, you're right. But as I said above: it is covered by this grid (or to be more exact: three grids) of hexagon-shaped pointings. Because I'm only plotting the center of the hexagon for clarity (otherwise the plot's totally cluttered), there are gaps between the points. These gaps are covered by the other six beams on the corners of the hexagon, fully covering the sky. The grey dots in the background show all observations done by Arecibo, the coloured ones are the ones we have at least partially analysed.

 

Einstein@Home Project

Mad_Max
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Thanks for the explanation.

Thanks for the explanation. It is now much clearer. Although as always answers raise new questions :)
Telescope range +/- 20 degrees plus the Earth's rotation around its axis gives us the "40° wide corridor" through space. But a rotation of the Earth around the Sun does not make it possible to cover a larger area?

> The quantization here is 1 / (628 * 7).
And the other possible parameters (except DM)? Does this mean that one APB WU (or 1/4 WU as one task of current APB2 includes 4 datasets) covers the entire parameters space (eg base spin frequency, the spindown rate, binary systems parameters, etc. except DM) for one skypoint? (ok, one beam from one of three grids for one skypoint)?

> The grey dots in the background show all observations done by Arecibo, the coloured ones are the ones we have at least partially analysed.

Great, this is a reply to a question that I was going to ask but forgot to write in previous post :)
Then another question on his replacement - big black gaps where there are no gray or colored dots - what is it? (In the central regions of the graphs. Closer to the edges of the apparently data collecting simply is not finished yet?) Malfunctions in the Arecibo detectors or/and data collection system and stops to service / repairs that occurred during data collection for the past 5 years? Or something blocked the observations at these points? (My assumption it may be the Sun and the Moon?)

Mike Hewson
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RE: But a rotation of the

Message 89023 in response to message 89022

Quote:
But a rotation of the Earth around the Sun does not make it possible to cover a larger area?


The Earth rotates with respect to an axis independent of orbital position & motion ( in the time frame of our observations ). What changes throughout the year is where the Sun ( or the planets ) lies on the Celestial sphere. If Aricebo looks at Solar system stuff then that would be of merit, with distant stuff not so.

Cheers, Mike.

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

Benjamin Knispel
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RE: Thanks for the

Message 89024 in response to message 89022

Quote:
Thanks for the explanation. It is now much clearer. Although as always answers raise new questions :)
Telescope range +/- 20 degrees plus the Earth's rotation around its axis gives us the "40° wide corridor" through space. But a rotation of the Earth around the Sun does not make it possible to cover a larger area?

Ok, this has already been answered correctly by Mike.

Quote:

> The quantization here is 1 / (628 * 7).
And the other possible parameters (except DM)? Does this mean that one APB WU (or 1/4 WU as one task of current APB2 includes 4 datasets) covers the entire parameters space (eg base spin frequency, the spindown rate, binary systems parameters, etc. except DM) for one skypoint? (ok, one beam from one of three grids for one skypoint)?

One of the ABP WUs consist of four so-called de-dispersed timeseries (that is: corrected for one trial value of DM). This timeseries is searched over the whole frequency range for all orbital parameters. There is no additional search over spin-down.

Quote:


> The grey dots in the background show all observations done by Arecibo, the coloured ones are the ones we have at least partially analysed.

Great, this is a reply to a question that I was going to ask but forgot to write in previous post :)
Then another question on his replacement - big black gaps where there are no gray or colored dots - what is it? (In the central regions of the graphs. Closer to the edges of the apparently data collecting simply is not finished yet?) Malfunctions in the Arecibo detectors or/and data collection system and stops to service / repairs that occurred during data collection for the past 5 years? Or something blocked the observations at these points? (My assumption it may be the Sun and the Moon?)

There just weren't done any observations by Arecibo in these gaps. I'm not sure why this actually happened, might be one or all of the above. It's however not about parts of the sky being hidden behind celestial bodies in our solar system. The PALFA survey started using a new instrument in March 2009 and re-observing the points in the sky done before with the old instrument at higher sensitivity and longer observation time.

 

Einstein@Home Project

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