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A faint discrete source origin for the highly ionized iron emission from the Galactic Centre region


The origin of the X-ray emission for the central region of our Galaxy has remained a mystery1,2,3,4. In particular, the relative spectral contributions of the diffuse emission and discrete sources, which are critical to understanding the high-energy phenomena in this environment, have been unclear because of the lack of sufficient spatial resolution. Here we report the results of a large-scale imaging survey of the Galactic Centre that resolves these components. We find that the Kα emission from iron that has been highly ionized (so that it has only two electrons left), which has previously been attributed to the diffuse component1, actually arises mainly from discrete sources. This suggests that the presence of a large amount of hot gas (T ≈ 108 K) is no longer required to explain the iron line emission. The spectra of the discrete sources indicate the presence of numerous accreting white dwarfs, neutron stars, and/or black holes in the region. The diffuse emission dominates over the contribution from the faint point sources, and is shown to be associated globally with interstellar features that have been observed at radio and mid-infrared wavelengths, suggesting that it is the product of recent massive star formation.

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Figure 1: Mosaic image of the Galactic Centre region.
Figure 2: Comparison of accumulated point-source (lower) and diffuse emission (upper) spectra.
Figure 3: A multiwavelength close-up of the recent massive star-forming region near the Galactic centre.

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We thank F. Jagodzinski for assistance in the data calibration, and L. Townsley for helping with the CTI corrections.

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Correspondence to Q. D. Wang.

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The authors declare no competing financial interests.

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Wang, Q., Gotthelf, E. & Lang, C. A faint discrete source origin for the highly ionized iron emission from the Galactic Centre region. Nature 415, 148–150 (2002).

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