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I've read that there are 4 distinct although related forms of AGs : Seyferts, Quasars, Radio and Blazars. Are there any other forms possible? Also do these forms ever intermix to give something new?

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a quick wiki search gives you an answer to all your questions. Try and make your question more specific – polyphant Jun 7 '14 at 16:36

Yes of course, there are other forms apart from the four stated above. Basically you have just two kinds:

  1. the radio-quiet, and
  2. the radio-loud.

But then again, there are two Seyferts

  1. Seyfert I, and
  2. Seyfert II

Apart from Quasar, Blazar and Radio galaxy, we also have presently,

  1. BL Lac (Named after its prototype BL Lacarte (original member of Blazar type)), and
  2. OVV (Optically Variable Violent Quasar or OVV Quasar; subtype of Blazar)

Best source to begin with is of course.

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What you've mentioned are basically the sub forms of the 4 prominent types. Its their inherent characteristics that distinguishes them into sub categories. My question was about any formats apart from these and if an intermix or aby-product (which is an AGN) is possible? – stp30 May 22 '14 at 10:45

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