[SEMINARI] [2 SEMINARIS] Bill Cotton, Radio and Optical Interferometry

[Enric Marco]

		    BILL COTTON
	National Radio Astronomy Observatory 
	      Charlottesville, EE.UU.


LUGAR: Seminario del Dpto. de Astronomia y Astrofisica


CONFERENCIA-1: Martes 17 de Junio, 16:00: 

			"Radio and Optical Interferometry"

 This talk will cover the basics of astronomical interferometry.
The underlying basic physical principles are developed by a 
comparison of the more widely understood radio interferometry 
with the use of currently developing optical/IR arrays. The 
implementation technology and practical constraints of radio and 
optical/IR interferometry are quite different, largely due to the
Heisenberg Uncertainty Principle which imposes a huge sensitivity
penalty on the detection of the phase of a photon at high 
frequencies.  This leads to "direct" interferometry in the 
optical/IR where the photons are first interfered and then the 
interference pattern detected, and "heterodyne" interferometry 
in the radio where the electric field of the incoming waves is 
detected and then fringes formed electronically.  These and other
practical technical details are explored.


CONFERENCIA-2: Jueves 19 de Junio, 16:00: 

		"Optical Interferometry: Astronomical Application"
			

  This talk surveys the astrophysical topics to which the newly
developing optical/IR interferometric techniques can be applied.  
A brief historical review and summary of past and current
interferometers in covered.  For a couple decades the poor
sensitivity of optical interferometry has limited its application
mainly to the study of bright stars, principally close multiple star
systems and stars with extended envelopes.  Especially in the cooler
stars with extended envelopes, line blanketing by the numerous
molecules means that spectroscopic measurements are insufficient to
determine effective temperatures and direct measurements of the
photospheric size are needed to test stellar models.  Recently the
development of interferometric arrays with large apertures up to 10 m
with adaptive optics have dramatically increased the sensitivity of
these arrays, allowing a wider range of astrophysical topics 
including AGNs, to be studied. Recent results on AGNs from the 
ESO MIDI/VLTI interferometer are discussed.

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/------------------------------------\
 Dr. Enric Marco
 Departament d'Astronomia i Astrofísica
 Facultat de Física
 Universitat de València
 C/  Dr. Moliner, 50
 46100 Burjassot, Spain
 Phone: (34)-96-354-3069
 Fax:(34)-96-354-3084
 enric.marco en uv.es
 http://www.uv.es/marco
 http://www.uv.es/aulaastronomia
 http://www.uv.es/daa
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