Date:   July 28, 2008 (Monday)
Time:   3:30 pm EDT (refreshments at 3:20 pm)
Place:  Green Bank Auditorium
         (Video: CV-AUD/AOC-AUD)

Speaker:  Yuri Kovalev, MPIfR, Bonn; ASC Lebedev, Moscow

Title:  "Nuclear opacity in active galactic nuclei and
recent results on the inner radio jet in M87"

Abstract:

In extragalactic jets, the apparent position of the compact, bright
emitting region at the narrow end of the jet (the core) depends on the
observing frequency, owing to synchrotron self-absorption and external
absorption. This dependency both provides a tool to probe absolute
geometry and physical conditions in the vicinity of the core and
possesses problems for astrometric studies using compact radio sources.
New observational evidence based on the first systematic VLBI study as
well as astrophysical and astrometric applications of the effect will be
discussed. Recent results from deep 2 cm VLBA monitoring of the inner
radio jet of M87 will be also presented.


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