M28?

Pavel_Kirpichenko
Pavel_Kirpichenko
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Topic 230946

The names of the tasks in the BRP 7 application contain the name M28. Does this name refer to a globular cluster from the Messier catalog?

astro-marwil
astro-marwil
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Hallo Pavel!May be. M28

Hallo Pavel!

May be. M28 is just 18.3 +/- 1 [KLy] away, and it's about 12[Gy] old. They assume, that in such globular clusters have to be lots of Neutron stars and so perhaps pulsars. Due to the high density of stars within the cluster, the chance for relativistic effects detectable in pulsar timing is much higher. That fits into the research program. And it's seeable by MEERKAT from the south of our earth. But ... I'm just an amateur astronomer.

Kind regards and happy crunching and happy Easter

Martin

Mike Hewson
Mike Hewson
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Yep, and as Martin says it

Yep. It has a known millisecond pulsar PSR B1821–24 : a dense neutron star rotating once every three milliseconds. In this case it has gamma ray emission (see here), as well as radio and X-ray pulse profiles (see here). It is described as 'exceptionally energetic'.

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

Pavel_Kirpichenko
Pavel_Kirpichenko
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Cool, thx! 

Cool, thx! 

 

Pavel_Kirpichenko
Pavel_Kirpichenko
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Is the pulsar PSR B1821–24

Is the pulsar PSR B1821–24 being investigated or is there a search for new pulsars in this cluster?

astro-marwil
astro-marwil
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Hello Pavel!They’re

Hello Pavel!

They’re searching for probable deviations from the GRT - General Relativity Theory - in the regime of high g - means strong gravitation fields, or better, heavy space-time curvature -. So, they will be happy to find more Pulsars in binary or triple systems in this dens volume.

Kind regards and happy crunching

Martin

Pavel_Kirpichenko
Pavel_Kirpichenko
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I see, thanks.

I see, thanks.

Mike Hewson
Mike Hewson
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From here (as of last March)

From here (as of last March) :

MeerKAT is an exciting new radio telescope, located in South Africa, that can search the Southern sky with more sensitivity, and with higher resolution than ever before. This means that there is a lot of data to search! Currently, the GPU-accelerated “BRP7” search is processing data from the TRAPUM survey. We are almost finished hunting for “black-widow” binaries in the globular clusters Messier 22, Messier 28, and Terzan 5. These are dense, spherical conglomerations of stars that harbour many rapidly rotating pulsars, especially in binary systems. After that is finished, we will search the data again, this time for looking double neutron star binaries.

I think we are now looking for those double neutron star binaries.

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

astro-marwil
astro-marwil
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Hello! Today at 09:06:05

Hello!

Today at 09:06:05 (UTC) I got the first tasks of Terzan 5 for my pipeline.

Kind regards and happy crunching

Martin

 

Mike Hewson
Mike Hewson
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Hi Martin! For your interest

Hi Martin! For your interest there is a fascinating recently published survey of Terzan 5 with many significant findings arising from examination of the TRAPUM data. Note also that two of the authors are from AEI in Hannover (P. V. Padmanabh & C. J. Clark), plus another from Swinburne University near where I live, all in all a multinational effort. 

From pages 21-22 of that preprint (my emphasis):

"The searches conducted on MeerKAT data so far have also been limited to acceleration searches down to 30 min segments. This implies that the searches are reasonably sensitive to binary pulsars with orbital periods of the order of hours rather than minutes. Applying jerk searches (Andersen & Ransom 2018) or coherent template bank based searches (Allen et al. 2013; Balakrishnan et al. 2022) can thus provide a possibility to find these highly compact binaries whose orbital period is of the order of few minutes. Such binaries can provide an excellent platform for testing GR in stronger gravitational fields than those of known binary pulsars. We are currently working with MeerKAT data to search for such systems using Einstein@Home (Anderson et al. 2006), a volunteer distributed computing project that has already been successful in the past for discovering several radio pulsars (see Knispel et al. 2015, and references therein)."

{Yes, that is Bruce Allen and Benjamin Knispel being referred to here.}

I am utterly gobsmacked by the idea/reality of two rapidly spinning pulsars orbiting each other in a matter of a few minutes. These are great tests, as you say, of GR in extreme circumstances*.

Cheers, Mike.

I also muse upon the idea of trinary systems etc ... what a place to go looking, eh?

(edit) Note that 'jerk searches' isn't a sociological comment but refers to the time derivative of acceleration, known as jerk. Further derivatives (of position with respect to time) are snap, crackle and pop. A non-zero jerk then means there is a changing acceleration. So snap tells you how jerk is changing, crackle how snap is changing, and pop how crackle is changing. From the breakfast cereal Kellogg's Rice Bubbles, I kid you not!

(edit) 'Roche lobe overflow' : a Roche lobe refers to the equipotential surface at which the gravitational binding (of a test mass) to each of the orbiting binary components are equal. If a particle is within a Roche lobe it will stay with it's star, as it were, while if beyond the Roche lobe it will tend toward the other star. The lobe has the shape of a teardrop with the smaller side of that pointing toward the companion. The really interesting case is when a star is larger than it's own Roche lobe and hence matter from the outer layers of that star will be siphoned off to the other component. If a pulsar is that other component then the in-fall of that material can 'spin up' said pulsar to faster revolutions. This leads to redback and black widow systems - that is one companion 'eats' the other - differentiated by their component masses, the redbacks being more massive than the black widows.

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

astro-marwil
astro-marwil
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Posts: 520
Credit: 441,849,966
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Hello Mike! It took some

Hello Mike!

It took some days before I could answer, because I’m bothered by a bad cold.

Thank-you for the link to the paper.

Some years ago, we had a lecture by a scientist from AIP (Astrophysical Institute Potsdam) about globular clusters at our amateur astronomical club. He said, that in such GCs the density of stars is so high, especially in the center, that very often neighbor stars come into the Roche limit. That is the reason, why the radial density of stars in GCs follow a Normal Distribution. I found it interesting in the paper you mentioned, shortly before the conclusions, that they have such interactions found : "... the detection of systems like Ter5ao, which are clearly the products of secondary exchange interactions, implies that other such systems might be found in Ter5." But, I assume, the time length of the closed approach might be too short to separate for deviations from GRT.

Kind regards and happy crunching

Martin

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