BROADENING OF THE IRON EMISSION-LINE IN MCG-6-30-15 BY COMPTONIZATION

We show that the iron K emission line from MCG-6-30-15 could be broade ned through Comptonization by a surrounding highly ionized cloud with radius similar to 10(14) cm. We calculate the temperature of the cloud to be similar to 0.21 keV, provided that a reasonable estimate of the UV flux is made. The X-ray/gamma-ray emission observed from the sourc e is compatible with this model. Such a cloud should be highly ionized , and strong absorption edges are not expected from the source. For a 10(6) M-circle dot black hole the size of the cloud corresponds to abo ut 300 Schwarzschild radii. The intrinsic line could then be emitted f ar from the black hole, and gravitational redshift and Doppler effects would be negligible. If the black hole mass is much larger than 10(6) M-circle dot, gravitational/Doppler redshifts would also contribute s ignificantly to the broadening. We argue that the broad red wing obser ved in the source does not by itself imply emission from regions close (R < 5r(S)) to the black hole. However, Comptonization cannot produce a double peak. The presence of such a feature is a clear sign of inne r disk emission influenced by gravitational and Doppler effects, perha ps broadened by the Comptonization. We note that simultaneous broadban d (2-100 keV) study of this source can also reveal (or rule out) the p resence of such a Comptonizing cloud.