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Profile Sebastian M. Bobrecki
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Message 78 - Posted: 24 Feb 2015, 15:06:20 UTC
Last modified: 24 Feb 2015, 15:08:58 UTC

There's always that someone has to start, so... what exactly "Universe X-ray sources" application is doing?
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Grzegorz Wiktorowicz
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Message 88 - Posted: 25 Feb 2015, 16:06:22 UTC - in response to Message 78.  

It's a good time to start explaining that! The Universe is full of X-ray sources, but we don't see them as the atmosphere is blocking all the radiation. Generally, stars have a very weak X-ray emission. However, interactions present in the binary systems (two stars bound by gravitation) could be powerful sources.
Of our main interest are systems where one star is the black hole and it accretes matter from its companion. This matter can't be transferred directly onto the black hole because it is very small. Therefore it forms a disk around black hole where the matter systematically loses energy due to friction and falls down. This process leads also to the strong growth of temperature in the disk and, as a consequence, to highly energetic radiation in the X-ray band.
This is a very general model and in this simulations we are going to check if it is possible to reproduce the observed sample of X-ray objects. They are of high importance as this X-ray binaries are the only places in the Universe where black holes are observed (indirectly). Shortly should be published our first article concerning this topic.
Grzegorz Wiktorowicz
National Astronomical Observatories,
Chinese Academy of Sciences
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Message 97 - Posted: 26 Feb 2015, 16:00:02 UTC - in response to Message 88.  

Thank you for your explanation!
So, in short, we are simulating a universe and look if the x-ray sources are in the simulation, where they were observed in the real universe, right?
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Grzegorz Wiktorowicz
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Message 98 - Posted: 26 Feb 2015, 16:53:21 UTC - in response to Message 97.  

Yes, you are right.

We have to simulate the whole Universe to have a valuable comparison with the number of observed sources. Currently, we concentrate on X-ray binaries as the black holes, whose formation mechanisms are still quite mysterious, were found only in these systems.
Grzegorz Wiktorowicz
National Astronomical Observatories,
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Message 156 - Posted: 12 Mar 2015, 18:12:23 UTC - in response to Message 98.  
Last modified: 12 Mar 2015, 18:13:16 UTC

What is difference between the old and new (v2) version of application? In addition to the obvious fact that the result files are smaller? Are we computing something different with it? Or maybe, it is just rejecting/losing/filtering some results?
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Message 159 - Posted: 13 Mar 2015, 8:19:07 UTC - in response to Message 156.  

In one word it is filtering. We moved the first step of analyzis to the simulation code, so now it is done on the volunteers' computers instead of our machines. It searches for the interesting phases of star's life and filters out the rest that we understand.

In the near future we are going to change the output in such a way that the simulation will run longer but the output files will be even smaller.
Grzegorz Wiktorowicz
National Astronomical Observatories,
Chinese Academy of Sciences
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Message 160 - Posted: 13 Mar 2015, 11:19:58 UTC - in response to Message 159.  

Thanks for the information Grzegorz.
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Message 388 - Posted: 29 Jun 2015, 8:45:11 UTC

Is there anything interesting you could actually tell us, Grzegorz?

Many WUs have been calculated since the article from April. Maybe there are some interesting new observations you could tell us about? =)
"I should bring one important point to the attention of the authors and that is, the world is not the United States..."
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Message 389 - Posted: 30 Jun 2015, 8:09:52 UTC - in response to Message 388.  

Thanks for this question! We are currently presenting the work on the international conference where it gets a wide interest. After the return I will put the poster and some interesting graphics on the page.

The previous work was done for a small subgroup of objects and that's why it took less time. Currently, we aim at simulating the whole population. It will not be possible without the large numerical power we have thanks to the participants of U@H project. Nevertheless, as several different models have to be checked, it still needs a lot of time to calculate. We will provide you with all the partial results as only we obtain them.
Grzegorz Wiktorowicz
National Astronomical Observatories,
Chinese Academy of Sciences
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Message 419 - Posted: 17 Jul 2015, 20:19:22 UTC - in response to Message 389.  

Thanks for this question! We are currently presenting the work on the international conference where it gets a wide interest. After the return I will put the poster and some interesting graphics on the page.

The previous work was done for a small subgroup of objects and that's why it took less time. Currently, we aim at simulating the whole population. It will not be possible without the large numerical power we have thanks to the participants of U@H project. Nevertheless, as several different models have to be checked, it still needs a lot of time to calculate. We will provide you with all the partial results as only we obtain them.


So, I am curious. Can you not piggy-back on the data other projects are gathering, such as Einstein?
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Message 427 - Posted: 18 Jul 2015, 16:17:59 UTC - in response to Message 419.  

Einstain@home is a totally different project. Firstly, they concentrate on the search for gravitational waves. Secondly, they process observations.

Nevertheless, we can cooperate. For example, we can predict what they should obtain. Some predictions for the gravitational radiation have been made with StarTrack code already (e.g., Figure 13 of http://arxiv.org/pdf/1110.1726v1).
Grzegorz Wiktorowicz
National Astronomical Observatories,
Chinese Academy of Sciences
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Message 540 - Posted: 15 Sep 2015, 18:22:51 UTC

What's new/different with v3 application? Some tasks have name like "universe_xray_3_Paulina_...". Are they something special?
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Message 542 - Posted: 16 Sep 2015, 10:56:53 UTC - in response to Message 540.  

Sorry for this silence on the forum. We are working on the introduction of the new code for the simulations. It will, hopefully, allow for long, uninterrupted calculations of several different models and investigation of a bunch of astrophysical problems. I will write a news today about that.

Concerning this a bit farcical file names, they were introduced just for easier recognition. This particular one is the model in which we investigate the influence of a different initial distribution of eccentricities for low-mass stars. It was proposed and developed by a person whose name is Paulina. We cooperate with her but she is not a member of the team (yet).

Don't hesitate to ask if you have further questions.
Grzegorz Wiktorowicz
National Astronomical Observatories,
Chinese Academy of Sciences
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Message 578 - Posted: 4 Oct 2015, 5:37:25 UTC

Hello and from me.
I would like to ask you if you think to make app to use GPU? Because i wnt to use my nvidia gpu for this project.
Best regards.
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Grzegorz Wiktorowicz
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Message 583 - Posted: 5 Oct 2015, 11:54:56 UTC - in response to Message 578.  

Hello!

Currently we are not planning that. However, the algorithm is perfect for GPU-computing and in the future we will for sure consider such an improvement.
Grzegorz Wiktorowicz
National Astronomical Observatories,
Chinese Academy of Sciences
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Message 585 - Posted: 6 Oct 2015, 18:12:36 UTC - in response to Message 583.  

However, the algorithm is perfect for GPU-computing and in the future we will for sure consider such an improvement.


Hoping for OpenCl....
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