A HOT GAS-MODEL FOR IRON-LINE X-RAY-EMISSION FROM THE RAPIDLY VARYING SEYFERT-GALAXY NGC6814

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 approximately 10(12) cm generates X-rays that produce the emission line by fluorescence of iron in a surrounding cold gas, which extends out to approximately 10(13) 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 approximately 6%.