THE BROAD EMISSION-LINE AND CONTINUUM VARIATIONS OF SEYFERT-GALAXIES .2. BROAD-LINE REGION STRUCTURE AND KINEMATICS

Spectroscopic observations of 13 Seyfert 1 galaxies made from 1979 to 1984 at Palomar and Steward Observatories were analyzed for Hbeta line profile variations. Significant profile changes were detected in five galaxies. These variations are often associated with changes in conti nuum and/or Hbeta strength, suggesting a causal connection between var iations in the continuum source and changes in emission-line profiles. Moreover, the overall strength of Hbeta line flux variations is stron gly correlated with line width in the far wings, whereas no such corre lation was found in the line core. This finding is consistent with pre vious observations (Shuder 1982) which suggest that higher velocity ga s lies closer to the central continuum source, since this inner gas wo uld be expected to track variations more closely. In each of the five galaxies in which Hbeta line profile variations were detected, particu larly NGC 5548 and Mrk 6, only two distinct line profile shapes were o bserved. Since intermediate profile types were not detected, the trans ition from one type to the other must occur rapidly (within a few mont hs). These rapid line profile variations are thus consistent with nume rous other studies which strongly point to a small broad-line region ( BLR) size in Seyfert galaxies. Observational models of BLR kinematics and structure for each of the galaxies in the present sample are prese nted. Line asymmetries suggest that radial motions exist in the BLRs o f most of these objects. Chaotic motions also appear to be quite commo n. However, evidence for rotational motion was observed in only one ca se. A model that is consistent with the majority of this sample incorp orates both radial and chaotic motions combined with some form of exte rnal obscuration such as an optically and geometrically thick torus.