Comparisons of various model fits to the iron line profile in MCG-6-30-15

The broad iron line in MCG -6-30-15 is fitted to the Comptonization model, in which line broadening occurs as a result of Compton down-scattering in a highly ionized optically thick cloud. These results are compared to the di sk line model, in which the broadening is due to gravitational/Doppler effe cts in the vicinity of a black hole. We find that both models fit the data well, and it is not possible to differentiate between them by fitting only the ASCA data. The best-fit temperature and optical depth of the cloud are found to be kT = 0.54 keV and tau = 4.0, respectively, from the Comptonizat ion model. This model further suggests that while the temperature can be as sumed to be constant, the optical depth varies during the observation perio d. We emphasize an earlier conclusion that simultaneous broadband data (3-5 0 keV) can rule out (or confirm) the Comptonization model.