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Proc. SPIE 4006: Interferometry in Optical Astronomy

The following papers were presented at the SPIE conference Interferometry in Optical Astronomy (part of Astronomical Telescopes and Instrumentation, 27-31 March 2000, Munich) by members of the COAST team:

Recent Astronomical Results from COAST

Oral presentation

PDF

John S. Young, John E. Baldwin, Roger C. Boysen, David F. Buscher, Amanda V. George,
Christopher A. Haniff, Debbie Pearson, John Rogers, Peter J. Warner,
Donald M. A. Wilson, and Richard W. Wilson*

Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

Craig D. Mackay

Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

* On secondment from: UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK

Abstract

We present the latest astronomical results from the Cambridge Optical Aperture Synthesis Telescope (COAST). COAST is a first-generation stellar interferometer, which uses an array of small (40 cm) separated telescopes to perform high-resolution imaging at visible and near-infrared wavelengths. The new science results from COAST exploit two recently-added capabilities of the COAST array, namely the ability to observe in any of the infrared J, H and K bands as well as at visible wavelengths, plus operation with five telescopes. We present contemporaneous observations of the red supergiant Betelgeuse at three wavelengths in the red and near-infrared. These data show that the apparent symmetry of the stellar disk is a strong function of wavelength, but that the bright spots seen in visible light are consistent with a convective origin. Data obtained using all five array elements on the symbiotic star CH Cygni reveal an elliptical distortion of the disk of the red giant, possibly related to mass transfer to a compact companion.

Keywords: interferometry, closure phase, imaging, infrared, supergiants, symbiotic stars

COAST: the current status

Poster presentation

PostScript

Christopher A. Haniff, John E. Baldwin, Roger C. Boysen, Amanda V. George, David F. Buscher,
Debbie Pearson, John Rogers, Peter J. Warner, Donald M. A. Wilson and John S. Young

Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

Craig D. Mackay

Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

Abstract

We present a summary of the status of the Cambridge Optical Aperture Synthesis Telescope (COAST). Since our last report we have concentrated on improving both the efficiency of use of the array and its astrophysical capabilities. In particular we have achieved useful improvements in throughput, detector sensitivity and the efficiency of securing measurements of visibility amplitudes and closure phases. With five telescopes fully operational, COAST is now being used routinely for parallel programs of astrophysics and as a technical test-bed for its proposed successor, the Large Optical Array - LOA.

Keywords: interferometry, closure phase, optical, infrared

Technologies for a cost-effective astronomical imaging array

Poster presentation

PostScript

David F. Buscher, John Rogers, John E. Baldwin, Roger C. Boysen, Amanda V. George, Christopher A. Haniff,
Debbie Pearson, Peter J. Warner, Donald M. A. Wilson and John S. Young

Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

Abstract

We discuss the design of the Large Optical Array, an optical/IR interferometer optimised for rapid imaging of complex astrophysical sources.

Keywords: imaging arrays, array geometry, beam combination, adaptive optics

Performance of new fringe-detecting APDs at COAST

Poster presentation

PDF

Amanda V. George, John E. Baldwin, Roger C. Boysen, Christopher A. Haniff, Debbie Pearson,
John Rogers, Peter J. Warner, Donald M. A. Wilson, and John S. Young

Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

Craig D. Mackay

Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

Abstract

At the Cambridge Optical Aperture Synthesis Telescope (COAST), first-generation photon-counting avalanche photodiodes (APDs) have been used as the pupil-plane fringe detectors in the optical regime. These are being replaced with EG&G's super-low k ('SLiK') APDs, which have an exceptionally low dark count (fewer than 100 counts per second) and high detection efficiency (up to 70% at 700nm). The new detectors have increased the limiting magnitude of the telescope, enabling the observation of targets previously too faint to be seen. We shall discuss the operation of these devices at COAST and present new interferometric observations of stellar objects at visible magnitudes of eight and fainter.

Keywords: detectors, optoelectronic devices, avalanche photodiode, APD, photon counting, fringe detection, optical, interferometry

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