A hot gas model for iron-line X-ray emission from the rapidly varying Seyfert galaxy NGC6814
Abstract
KUNIEDA et al.1 have observed rapidly varying X-ray continuum emission, along with an emission line at 6.4 keV, from the Seyfert I galaxy NGC6814. They suggest that a central energy source of radius ~1012 cm generates X-rays that produce the emission line by fluorescence of iron in a surrounding cold gas, which extends out to ~1013 cm. But in this model the intense X-irradiation needed to explain the line intensity would heat the surrounding gas to too high a temperature to allow the existence of the low ionization state needed to account for the wavelength of the line. I argue here, therefore, that the line is generated by hot gas, closer to the central energy source, and that the observed wavelength corresponds to the energy of a higher ionization state of iron, gravitationally redshifted by ~6%.
- Publication:
-
Nature
- Pub Date:
- May 1991
- DOI:
- 10.1038/351214a0
- Bibcode:
- 1991Natur.351..214H
- Keywords:
-
- Galactic Radiation;
- High Temperature Gases;
- Iron;
- Metallicity;
- Seyfert Galaxies;
- X Rays;
- Astronomical Models;
- Continuous Radiation;
- Emission Spectra;
- Line Spectra;
- Astrophysics