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Hard X-ray image made by Swift and fields-of-view of Suzaku CCD camera. The figure is made by DARTS JUDO You can display the same figure with JUDO by clicking here

Universe seen with "hard" X-rays

The X-ray is electromagnetic wave with high energies. Therefore, the X-ray astronomy is also called as "high energy astronomy". We call low energy X-rays as "soft X-rays" and high energy X-rays as "hard X-rays", though its boundary is not clearly defined. Japanese ASCA satellite is the first one that captured the hard X-ray images above 2 keV. It is technically very difficult to focus hard X-rays with mirrors and detect them. The successor of ASCA, Suzaku is also able to image sky with hard X-rays above 2 keV, up to about 10 keV. However, higher energy X-rays penetrate the satellite, hence we may not obtain such hard X-ray images with Suzaku. The background of this picture indicates the hard X-ray image of the Galactic center region from 14 to 195 keV, by NASA's Swift satellite. Swift employs a completely different technology from ASCA or Suzaku, and is able to image sky with such high energy hard X-rays (but its imaging capability is limited). Here, we show Suzaku CCD fields-of-view on the Swift image. There are many black holes and neutron stars emitting strong hard X-rays near the Galactic center. Combining Suzaku and Swift, we can observe these targets in a wide energy range. In this manner, we can study characteristics of these X-ray sources in detail making use of the strengths of the two satellites.

Ken Ebisawa (ISAS/JAXA)

December, 2010