NOAO >   Observing Info >   Approved Programs >   2000A-0324

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Proposal Information for 2000A-0324


PI: Michael Eracleous, Pennsylvania State University, mce@astro.psu.edu
Address: 525 Davey Lab, University Park, PA 16802, U.S.A.

CoI: Jules P. Halpern, Columbia University
CoI: Thaisa Storchi-Bergmann, IF-UFRGS, Brasil

Title: Long-Term Monitoring of Dynamical Motions in the Accretion Disks of AGNs

Abstract: Our ongoing long-term study of ``disk-like'' emission lines in AGNs has demonstrated that the accretion disk is indeed the most likely origin of these double-peaked lines. They must be rather common too, since they often appear in nearby LINERs. In the course of our study we have found that most of these double-peaked line profiles vary dramatically on time scales of months to years. The observed variability time scale is compatible with the dynamical time in an accretion disk at several hundred gravitational radii. We are comparing the observed evolution of the line profiles with detailed models of dynamical phenomena that are thought to occur in disks. These applications will provide direct measurements of the black hole mass, and will evaluate models for tidal disruption of stars, elliptical accretion rings, spiral waves in accretion disks, and accretion-disk winds. The full range of profile variability may take decades to characterize, but for now we make a modest proposal to continue our long- term monitoring, observing the variable line profiles twice a year for another six years. It is apparent from a decade's worth of data that there are specific patterns in the variability of the line profiles. The most important observational fact that we now need to learn is whether the observed variations are regular and periodic. The proposed observing runs at NOAO will contribute approximately half of the quarterly monitoring intervals that we need to adequately sample the variability, with other telescopes filling in the rest.


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