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		| Paper: | 
		Long Term Profile Variability of Double-Peaked Emission Lines in AGNs | 
	 
	
		| Volume: | 
		311, AGN Physics with the Sloan Digital Sky Survey | 
	 
	
		| Page: | 
		193 | 
	 
	
		| Authors: | 
		Lewis, K.T.; Eracleous, M.; Halpern, J.P.; Storchi-Bergmann, T. | 
	 
	
	
		| Abstract: | 
		An increasing number of AGNs exhibit broad, double-peaked Balmer emission lines, which are thought to arise from the outer regions of the accretion disk which fuels the AGN. The line profiles are observed to vary on a characteristic timescales of 5-10 years. The variability is not a reverberation effect; it is a manifestation of physical changes in the disk. Our group has monitored a set of 20 double-peaked emitters for the past 8 years (longer for some objects). Here, we characterize the variability of the double-peaked Hα line profiles in five objects from our sample. By experimenting with simple models, we find that disks with a single precessing spiral arm are able to reproduce many of the variability trends that are seen in the data.  | 
	 
	
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