Pulsar re-detections in PALFA data

Bikeman (Heinz-Bernd Eggenstein)
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RE: RE: So we have more

Message 93885 in response to message 93884

Quote:
Quote:
So we have more succes by using the LIGO data then that of arecibo, if we would.
Well we're trying to get Einstein's theories checked, not only to find (double)pulsars

Yep, plus I reckon there'll be stuff quite unexpected. :-)

Quote:
I have seen the Effelsberg 100M directing telescope.
1 of the 2 largest in the world. Massive device :D

That's a terrific looking gadget, and looks like it has one axis to rotate. The beauty of parabolic dishes!

Cheers, Mike.

Effelsberg has a two axis alt-azimuth "mount" so you can point it to any point in the visible sky. It's no longer the biggest steerable radio telescope (Green Banks is bigger), but I think it's more beautiful :-) .

CU
Bikeman

Mike Hewson
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RE: Effelsberg has a two

Message 93886 in response to message 93885

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Effelsberg has a two axis alt-azimuth "mount" so you can point it to any point in the visible sky. It's no longer the biggest steerable radio telescope (Green Banks is bigger), but I think it's more beautiful :-).


It looks like a wine glass! So beneath the trees in the foreground of that photo is the other axis?

Cheers, Mike.

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

Bikeman (Heinz-Bernd Eggenstein)
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RE: RE: Effelsberg has a

Message 93887 in response to message 93886

Quote:
Quote:
Effelsberg has a two axis alt-azimuth "mount" so you can point it to any point in the visible sky. It's no longer the biggest steerable radio telescope (Green Banks is bigger), but I think it's more beautiful :-).

It looks like a wine glass! So beneath the trees in the foreground of that photo is the other axis?

Cheers, Mike.

Yup, it's better visisble here.

Amazing. It's not trivial to build a telescope of this size, a lesson that was learnt the hard way when the predecessor of the current Green Bank telescope collapsed in a sudden structural failure.

Mark
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RE: Hi Marty, E@H is

Message 93888 in response to message 93872

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Hi Marty,

E@H is currently processing about 18 minutes of Arecibo data per day. We think that, via various tricks, improvements, optimizations, and GPU-enablings, we can increase this processing speed by almost an order of magnitude, to about 2 hours/day. This would enable us to catch up on the PALFA data set (which on average is about an hour of data per day).

Cheers,
Bruce

Now that we have done the GPU and other stuff, where are we at?

Benjamin Knispel
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The re-discovery page has

The re-discovery page has been updated today to include the latest re-discoveries made by the project.

In total there are now 26 re-observations of 17 different radio pulsars, some of which were known before the observations were done with Arecibo, some of which were discovered in the course of the survey a few years ago.

As usual you can check whether you are among the two users who successfully crunched the WU that showed the candidate with the highest signifiance.

Cheers,
Ben

 

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Tom Philippart
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I just checked the

I just checked the re-discoveries page and a thing that struck me is that not all the pulsars look approximately the same.

The "normal" pulsar should look like a gaussian function (bell curve) as far as I know, however on the first result for instance this gaussian shape isn't visible to me.

Could this me some radio interferrence like they're having at seti?

Thanks in advance!

Mike Hewson
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RE: I just checked the

Message 93891 in response to message 93890

Quote:

I just checked the re-discoveries page and a thing that struck me is that not all the pulsars look approximately the same.

The "normal" pulsar should look like a gaussian function (bell curve) as far as I know, however on the first result for instance this gaussian shape isn't visible to me.

Could this me some radio interferrence like they're having at seti?

Thanks in advance!


I'm pretty sure this depends more so on the presumed mechanism of radiation, also on the exact orientation of the beam toward us, plus any filtering from intervening material on it's way to us. It 'looks' like an extended source on the surface of the neutron star, and the profile given is an average over many pulses - there is considerable beat-to-beat variation. Mind you I can't for the life of me see the profile in the plot for J1922+1733, is it that denser part of the thicket at DM ~ 350 ? :-)

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: Mind you I can't for

Message 93892 in response to message 93891

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Mind you I can't for the life of me see the profile in the plot for J1922+1733, is it that denser part of the thicket at DM ~ 350 ? :-)


Hi Mike,

you won't see the profile in this plot. This plot shows the detection statistic as a function of the spin frequency and the DM of the pulsar. A signal in a data set is a somewhat peak-like, cuspy structure in this plot (as you can see for the other pulsars). The shape of this peak depends a bit on the pulse profile but does not show the pulse profile as such.

The quoted peak however is fairly difficult to see for this one because this pulsar was emitting pulses only for about 20 seconds during the total 268 seconds of the observation. That's why the peak fairly weak, but is shown as this "denser part of the thicket" at DM channel ~350.

The pulse profile can be seen in the PRESTO plot, upper left corner. It's also definitely not a simple Gaussian shape, which you would not expect. Astronomers are not exactly sure why there's this substructure in the pulses but it might have to do with the exact shape of the emitting regions and the orientation of the beam and the line of sight, as you already said.

Cheers,
Ben

 

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Mike Hewson
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RE: Hi Mike, you won't see

Message 93893 in response to message 93892

Quote:

Hi Mike,

you won't see the profile in this plot. This plot shows the detection statistic as a function of the spin frequency and the DM of the pulsar.


So that's why I can't see it! :-)

Blush, of course ..... the graphic on the right side.

Quote:
The quoted peak however is fairly difficult to see for this one because this pulsar was emitting pulses only for about 20 seconds during the total 268 seconds of the observation. That's why the peak fairly weak, but is shown as this "denser part of the thicket" at DM channel ~350.


So I'd guess that would imply some reason at source to change the beam orientation on that timescale? Like it's in orbit around something, or precessing, so that the observation interval only partly overlapped it's interval of favourable alignment ( so the 20 seconds were contiguous? ). Could the mechanism turn on/off that quickly while we are still favourably aligned? I can see why these objects fascinate so .....

Quote:
The pulse profile can be seen in the PRESTO plot, upper left corner. It's also definitely not a simple Gaussian shape, which you would not expect. Astronomers are not exactly sure why there's this substructure in the pulses but it might have to do with the exact shape of the emitting regions and the orientation of the beam and the line of sight, as you already said.


Is there a current 'best' model for the emission mechanism(s)?

Cheers, Mike.

( edit ) I'm thinking the 'shape' is not reflecting some source characteristic that generates radiation in that pattern per se - but more that pulsar surfaces generically emit stuff roughly non-directionally but the magnetic ( and gravitational ) field constrains the path of escape to the distant universe. Sort of like blowing smoke rings, which you get by passage through a constriction and not ( necessarily ) because you burned material in donut pattern. A sort of aurora in reverse.

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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Hi all, just to get this

Hi all,

just to get this thread updated:
we've just refreshed the re-discovery page. We're now at 31 detections of 19 different known pulsars, meaning we detect one pulsar about once a week.

The latest one we found is a very interesting one. J1939+2134 is the second fastest spinning known pulsar, rotating at incredible 691 Hz!

Cheers,
Ben

 

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