We study the evolution of the broad, double-peaked H emission-line profile of the LINER/Seyfert 1 nucleus of NGC 1097, using 24 spectra obtained over a time span of 11 years-from 1991 November through 2002 October. While in the first 5 years the main variation was in the relative intensity of the blue and red peaks, in the last years we have also observed an increasing separation between the two peaks, at the same time as the integrated flux in the broad line has decreased. We propose a scenario in which the emission originates in an asymmetric accretion disk around a supermassive black hole, whose source of ionization is getting dimmer, causing the region of maximum emission to come closer to the center (and thus to regions of higher projected velocity). We use the observations to constrain the evolution of the accretion disk emission and to evaluate two models: the elliptical-disk model previously found to reproduce the observations from 1991 to 1996 and a model of a circular disk with a single spiral arm. In both models the peak emissivity of the disk drifts inward with time, while the azimuthal orientation of the elliptical-disk or the spiral pattern varies with time. In the case of the spiral-arm model, the whole set of data is consistent with a monotonic precession of the spiral pattern, which has completed almost two revolutions since 1991. Thus, we favor the spiral-arm model, which, through the precession period, implies a black hole mass that is consistent with the observed stellar velocity dispersion. In contrast, the elliptical-disk model requires a mass that is an order of magnitude lower. Finally, we have found tentative evidence of the emergence of an accretion disk wind, which we hope to explore further with future observations.

We present 888 visual-wavelength spectra of 122 nearby type II supernovae (SNe II) obtained between 1986 and 2009, and ranging between 3 and 363 days post-explosion. In this first paper, we outline our observations and data reduction techniques, together with a characterization based on the spectral diversity of SNeII. A statistical analysis of the spectral matching technique is discussed as an alternative to nondetection constraints for estimating SN explosion epochs. The time evolution of spectral lines is presented and analyzed in terms of how this differs for SNe of different photometric, spectral, and environmental properties: velocities, pseudo-equivalent widths, decline rates, magnitudes, time durations, and environment metallicity. Our sample displays a large range in ejecta expansion velocities, from ∼9600 to ∼1500 km s −1 at 50 days post-explosion with a median a H value of 7300 km s −1. This is most likely explained through differing explosion energies. Significant diversity is also observed in the absolute strength of spectral lines, characterized through their pseudo-equivalent widths. This implies significant diversity in both temperature evolution (linked to progenitor radius) and progenitor metallicity between different SNeII. Around 60% of our sample shows an extra absorption component on the blue side of the a H P-Cygni profile ("Cachito" feature) between 7 and 120 days since explosion. Studying the nature of Cachito, we conclude that these features at early times (before ∼35 days) are associated with Si II l6355, while past the middle of the plateau phase they are related to high velocity (HV) features of hydrogen lines.