THE VARIABILITY OF THE DOUBLE-PEAKED BALMER LINES IN THE ACTIVE NUCLEUS OF NGC-1097

We present spectroscopic observations of the nucleus of the Seyfert/lo w-ionization nuclear emission-line region galaxy NGC 1097 spanning the period 1991-1994. The goal was to monitor anticipated variations of t he broad, double-peaked Balmer fines which appeared abruptly in 1991. We find that the broad Balmer lines have varied significantly over the monitoring period, both in their integrated fluxes and in their profi le shapes. The integrated H alpha flux has decreased by a factor of 2, the H alpha/H beta ratio has increased, and the originally asymmetric H alpha profile has become symmetric. The decline of the H alpha flux and the change in the H alpha/H beta ratio can be interpreted as cons equences of either increased obscuration along the line of sight, or a decline in the ionizing continuum, but neither of these scenarios can account for the change in profile shapes. A model attributing the lin e emission to a precessing elliptical ring around a 10(6) M. nuclear b lack hole can reproduce the observed profile variations. In this scena rio, the line-emitting ring is the result of the tidal disruption of a star by the black hole. Alternative scenarios associating the broad-l ine emission with a collimated bipolar outflow also remain viable, but binary black holes and inhomogeneous accretion disks are disfavored b y the observed pattern of variability.