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TOP > Report & Column > The Forefront of Space Science > 2008 > Real Identity of “Dark Particle AcceleratorETo Be Explored by “SUZAKUE/span>

The Forefront of Space Science

Real Identity of “Dark Particle AcceleratorETo Be Explored by “SUZAKUE><br>
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Unveil the real identity of the bodies by SUZAKU!

To reveal scientifically, not imagination, real identity of the dark particle accelerators, it is important to observe in detail around the accelerators in various wavelengths other than TeV gamma ray and locate bodies in question. In above I wrote that “we cannot locate the bodies.EStrictly speaking, we are unsure whether we cannot locate them because they are really “darkEor we have not yet found them simply because we have not yet observed.

Coincidentally, 2005, when the dark particle accelerators were discovered, is the year when a Japanese X-ray astronomical satellite SUZAKU was launched. Since SUZAKU can perform low noise observation compared to X-ray astronomical satellites currently operated by Europe ant the U.S., it is good at detecting faint X-rays coming from the accelerators, which are predicted to be dark in X-ray. And, even if the accelerators would be very high-density stars (i.e., neutron stars) like the Crab Nebula, which formed after star’s death by explosion, or nebula around such stars, we thought that we could detect rotation movement of the stars because a hard X-ray detector onboard SUZAKU has good temporal resolution.

Then, we observed HESS J1616-508, one of candidates of dark particle accelerators, by SUZAKU just two months after its launch. We excited to open the data retrieved from the satellite but found that there was no image of bright body in the data. That was the moment that we convinced that the accelerator was “reallyEdark in X-ray. With more in-depth data analysis, it was discovered that its radiation energy in X-ray was only 2% of its TeV gamma ray. This value is the “dark particle accelerator’s recordEthat has not been broken from 3 years ago to date. SUZAKU revealed that the accelerator was really new population by the fact that it could not see the accelerator in X-ray.

However, as dark particle accelerators were the big discovery in the 21st century, story concerning them did not simply end at that point. In the center of the next accelerator candidate HESS J1804-216 observed by SUZAKU, we found an X-ray body though it was dark. With this discovery, we were partly delighted to get a clue to unveil and we got partly discouraged. Under such mixed feeling, we observed the third accelerator candidate HESS J1614-518. In the image taken by SUZAKU, X-ray radiation extended to the almost same degree as that of TeV gamma ray. There were no similar results among these three candidates. They showed quite different properties respectively.

After that, SUZAKU continually observed the accelerators candidates. As a result, we became aware that the accelerators had various facets in X-ray although they looked similar in gamma ray. One showed the similar shape as TeV gamma ray. One was more compact. One showed difference in position of its bright area. When sorting the accelerators, they were classified into several patterns.

It was thought that supernova remnant like SN 1006 was the most probable premise on accelerators. But number of body that was judged to be a remnant was only one. There were several bodies that were really dark in X-ray. It is guessed that they shine in only TeV gamma rays because of cosmic raysEcollision with molecular clouds. However we have not yet obtained any direct evidence to validate our guess. For the ten-odd accelerators, about half of the observed ones, we found out gloomily extended X-ray radiation similar to that of TeV gamma rays thanks to the low-noise observation capability of SUZAKU. We continue our research with the assumption that most of these extended bodies would be neutron stars or nebula around the stars. In fact, for an X-ray object located at HESS J1837-069, one of accelerator candidates, SUZAKU detected periodical variation of about 70 msec like that of the Crab Nebula by taking advantage of its high-temporal resolution capability. We believe that this indicates a scene where a neutron star hidden in the dark particle accelerator rotates at extremely high-speed.


Figure 2
Figure 2. Former dark particle accelerator HESS J1837-069, of which identity was confirmed to be a neutron star and nebula in the vicinity. Color image and contour line are by SUZAKU and HESS respectively. The lower left figure shows profile of brightness change caused by high-speed rotation of the star, which was measured by SUZAKU.



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