Diffuse emission spectrum of the central part of M82, obtained from the Chandra ACIS-S. The flux density is in units of 10 −14 erg s −1 cm −2 keV −1 . Upper panel: The 0.7-8 keV spectrum; Lower panel: The Fe K band spectrum of the same data. The three vertical dotted-lines indicates the expected centroid energies of 6.4 keV, 6.7 keV and 6.96 keV for cold Fe K, Fe xxv and Fe xxvi, respectively. The grey line indicates the fitted model of a power-law and three Gaussian lines.

Contexts in source publication

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... the soft X-ray emission spectrum is beyond the scope of this work, it is worth illustrating the contrasting characteristics of the emission-line spectrum above and below 4 keV. The broad-band spectrum (Fig. 2) shows strong He-like and H-like K-shell emission from Ne, Mg, Si, S, Ar and Ca in the 1-4 keV range. At energies above 4 keV, the most prominent spectral feature is the Fe K complex in 6-7 keV (Fig. 2), dominated by Fe xxv at ∼ 6.7 keV. As previously noted by Strickland & Heck- man (2007); Liu et al. (2014), a cold Fe K line at 6.4 keV ...

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... this work, it is worth illustrating the contrasting characteristics of the emission-line spectrum above and below 4 keV. The broad-band spectrum (Fig. 2) shows strong He-like and H-like K-shell emission from Ne, Mg, Si, S, Ar and Ca in the 1-4 keV range. At energies above 4 keV, the most prominent spectral feature is the Fe K complex in 6-7 keV (Fig. 2), dominated by Fe xxv at ∼ 6.7 keV. As previously noted by Strickland & Heck- man (2007); Liu et al. (2014), a cold Fe K line at 6.4 keV is also present. A line-like excess is detected marginally at 4.5 keV, although the origin is unclear. Since its detection is marginal and is not essential for this work, we leave further details in ...

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... Fe K line complex (Fig. 2) is described here by multiple Gaussians. The dominant Fe xxv is most likely of thermal origin. It is a triplet that is not resolved at the CCD resolution. Fitting a single Gaussian to a simulated apec spectrum gives a centroid energy of 6.68 keV with a slight broadening of σ ∼ 30 eV, when kT is in the range of 4-6 keV (Appendix A), ...

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... , which is the probability-weighted mean over the expected metallicity range of 1-5 Z . Their proportions of the total 4-8 keV flux in each spectrum are given in Table 4 (where the contribution of the 4.5 keV and 6.4 keV lines are left out). With the same set of spectral components, a spectral decomposition for the total diffuse emission spectrum (Fig. 2) is illustrated in Fig. 14. The relative contributions of the respective components are also given in Table ...