Transmission- to reflection-dominated spectral transitions in Seyfert 2 galaxies

Reflectiondominated Seyfert 2 galaxies are usually interpreted in terms of anactive nucleus covered by a Comptonthick absorber. However, recentserendipitously discovered transitions between reflection (R) andtransmissiondominated (T) states are more convincingly explained as changes inthe activity level of the AGN. If this is true, a substantial fraction of RSeyfert 2s may actually correspond to lowactivity states, rather than toheavily obscured AGN. We propose to observe an optically defined, complete andunbiased sample of Comptonthick Seyfertvirgul2 galaxies during the XMMNewton AO2,to measure on a sound statistical basis the rate of R to T transitions. Werequest to observe 8 objects for a total allocation time of 100 ks. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]