Abstract


Echo Mapping of Broad Hbeta Emission in NGC 5548
Horne, K., Welsh, W.F., and Peterson, B.M. 1991, ApJ, 367, L5

A one-dimensional echo map of the broad Hbeta emission-line region in the Seyfert 2 galaxy NGC 5548 is reconstructed by using a maximum entropy technique to model the variable optical continuum and integrated Hbeta emission-line fluxes observed during the 1989-1990 monitoring campaign as reported by Peterson et al. The echo map has a strong peak at time delay of 20 lt-days which has an unresolved width of 20 days at half maximum. The Hbeta response at time delay zero is less than one-third of that at 20 days, implying a deficit of Hbeta-emitting gas near the line of sight to the continuum source. This rules out spherically symmetric and edge-on disk geometries for isotropically emitting Hbeta clouds. Further monitoring will be necessary to determine the reliability of secondary structure in the echo map at 100-180 days.


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