Long-term profile variability of double-peaked emission lines in active galactic nuclei, and, Follow-up observations of candidate tidal disruption events

We present the results of over 15 years of spectroscopic monitoring of the broad, double-peaked Ha lines in a sample of seven broad-line radio galaxies with extremely broad, double-peaked line profiles that are well modeled by emission from photoionized gas in a relativistic Keplerian accretion disk around a central black hole. We use the long-term profile variability of the broad Ha lines to rule out alternative "non-accretion disk" scenarios for the source of the broad double peaked line emission, test models for dynamical processes in the accretion disk, and measure physical parameters of the accretion disk and its central black hole.; Luminous UV/X-ray flares are predicted to occur in the nuclei of inactive galaxies when a star is tidally disrupted by the galaxy's central supermassive black hole, and the bound fraction of the tidal debris is accreted. The ROSAT All-Sky Survey detected several large amplitude, soft X-ray flares from galaxies with no previous evidence for AGN activity, which were best explained as tidal disruption events. We obtained follow-up optical spectroscopy of three of the flaring galaxies a decade later with the STIS and a narrow slit to search for or place stringent limits on the presence of any persistent Seyfert-like emission in their nuclei. Two of the galaxies, RX J1624.9+7554 and RX J1242.6-1119, show no evidence for emission lines or a non-stellar continuum in their HST nuclear spectra, consistent with their ground-based classification as inactive galaxies. They remain the most convincing examples of tidal disruption events to date. The GALEX Ultra-Deep Imaging Survey (UDIS) has the ideal depth, wavelength coverage, and temporal sampling for detecting flares from tidal disruption events in the nuclei of galaxies over a large range of redshifts. We describe an analysis of the capability of GALEX to detect tidal disruption events, and describe our Chandra target-of-opportunity rapid follow-up X-ray imaging program to catch the early phase of the decay of the tidal disruption flares we discover in the UDIS.